机械加工毕业设计外文翻译--淬硬齿轮的加工
机械加工毕业论文中英文资料外文翻译文献
毕业论文中英文资料外文翻译文献附录附录1：英文原文Selection of optimum tool geometry and cutting conditionsusing a surface roughness prediction model for end milling Abstract Influence of tool geometry on the quality of surface produced is well known and hence any attempt to assess the performance of end milling should include the tool geometry. In the present work, experimental studies have been conducted to see the effect of tool geometry (radial rake angle and nose radius) and cutting conditions (cutting speed and feed rate) on the machining performance during end milling of medium carbon steel. The first and second order mathematical models, in terms of machining parameters, were developed for surface roughness prediction using response surface methodology (RSM) on the basis of experimental results. The model selected for optimization has been validated with the Chi square test. The significance of these parameters on surface roughness has been established with analysis of variance. An attempt has also been made to optimize the surface roughness prediction model using genetic algorithms (GA). The GA program gives minimum values of surface roughness and their respective optimal conditions.1 IntroductionEnd milling is one of the most commonly used metal removal operations in industry because of its ability to remove material faster giving reasonably good surface quality. It is used in a variety of manufacturing industries including aerospace and automotive sectors, where quality is an important factor in the production of slots, pockets, precision moulds and dies. Greater attention is given to dimensional accuracy and surface roughness of products by the industry these days. Moreover, surface finish influences mechanical properties such as fatigue behaviour, wear, corrosion, lubrication and electrical conductivity. Thus, measuring and characterizing surface finish can be considered for predicting machining performance.Surface finish resulting from turning operations has traditionally received considerable research attention, where as that of machining processes using multipoint cutters, requires attention by researchers. As these processes involve large number of parameters, it would bedifficult to correlate surface finish with other parameters just by conducting experiments. Modelling helps to understand this kind of process better. Though some amount of work has been carried out to develop surface finish prediction models in the past, the effect of tool geometry has received little attention. However, the radial rake angle has a major affect on the power consumption apart from tangential and radial forces. It also influences chip curling and modifies chip flow direction. In addition to this, researchers [1] have also observed that the nose radius plays a significant role in affecting the surface finish. Therefore the development of a good model should involve the radial rake angle and nose radius along with other relevant factors.Establishment of efficient machining parameters has been a problem that has confronted manufacturing industries for nearly a century, and is still the subject of many studies. Obtaining optimum machining parameters is of great concern in manufacturing industries, where the economy of machining operation plays a key role in the competitive market. In material removal processes, an improper selection of cutting conditions cause surfaces with high roughness and dimensional errors, and it is even possible that dynamic phenomena due to auto excited vibrations may set in [2]. In view of the significant role that the milling operation plays in today’s manufacturing world, there is a need to optimize the machining parameters for this operation. So, an effort has been made in this paper to see the influence of tool geometry(radial rake angle and nose radius) and cutting conditions(cutting speed and feed rate) on the surface finish produced during end milling of medium carbon steel. The experimental results of this work will be used to relate cutting speed, feed rate, radial rake angle and nose radius with the machining response i.e. surface roughness by modelling. The mathematical models thus developed are further utilized to find the optimum process parameters using genetic algorithms.2 ReviewProcess modelling and optimization are two important issues in manufacturing. The manufacturing processes are characterized by a multiplicity of dynamically interacting process variables. Surface finish has been an important factor of machining in predicting performance of any machining operation. In order to develop and optimize a surface roughness model, it is essential to understand the current status of work in this area.Davis et al. [3] have investigated the cutting performance of five end mills having various helix angles. Cutting tests were performed on aluminium alloy L 65 for three milling processes (face, slot and side), in which cutting force, surface roughness and concavity of a machined plane surface were measured. The central composite design was used to decide on the number of experiments to be conducted. The cutting performance of the end mills was assessed usingvariance analysis. The affects of spindle speed, depth of cut and feed rate on the cutting force and surface roughness were studied. The investigation showed that end mills with left hand helix angles are generally less cost effective than those with right hand helix angles. There is no significant difference between up milling and down milling with regard tothe cutting force, although the difference between them regarding the surface roughness was large. Bayoumi et al.[4] have studied the affect of the tool rotation angle, feed rate and cutting speed on the mechanistic process parameters (pressure, friction parameter) for end milling operation with three commercially available workpiece materials, 11 L 17 free machining steel, 62- 35-3 free machining brass and 2024 aluminium using a single fluted HSS milling cutter. It has been found that pressure and friction act on the chip – tool interface decrease with the increase of feed rate and with the decrease of the flow angle, while the cutting speed has a negligible effect on some of the material dependent parameters. Process parameters are summarized into empirical equations as functions of feed rate and tool rotation angle for each work material. However, researchers have not taken into account the effects of cutting conditions and tool geometry simultaneously; besides these studies have not considered the optimization of the cutting process.As end milling is a process which involves a large number f parameters, combined influence of the significant parameters an only be obtained by modelling. Mansour and Abdallaet al. [5] have developed a surface roughness model for the end milling of EN32M (a semi-free cutting carbon case hardening steel with improved merchantability). The mathematical model has been developed in terms of cutting speed, feed rate and axial depth of cut. The affect of these parameters on the surface roughness has been carried out using response surface methodology (RSM). A first order equation covering the speed range of 30–35 m/min and a second order equation covering the speed range of 24–38 m/min were developed under dry machining conditions. Alauddin et al. [6] developed a surface roughness model using RSM for the end milling of 190 BHN steel. First and second order models were constructed along with contour graphs for the selection of the proper combination of cutting speed and feed to increase the metal removal rate without sacrificing surface quality. Hasmi et al. [7] also used the RSM model for assessing the influence of the workpiece material on the surface roughness of the machined surfaces. The model was developed for milling operation by conducting experiments on steel specimens. The expression shows, the relationship between the surface roughness and the various parameters; namely, the cutting speed, feed and depth of cut. The above models have not considered the affect of tool geometry on surface roughness.Since the turn of the century quite a large number of attempts have been made to find optimum values of machining parameters. Uses of many methods have been reported in the literature to solve optimization problems for machining parameters. Jain and Jain [8] have usedneural networks for modeling and optimizing the machining conditions. The results have been validated by comparing the optimized machining conditions obtained using genetic algorithms. Suresh et al. [9] have developed a surface roughness prediction model for turning mild steel using a response surface methodology to produce the factor affects of the individual process parameters. They have also optimized the turning process using the surface roughness prediction model as the objective function. Considering the above, an attempt has been made in this work to develop a surface roughness model with tool geometry and cutting conditions on the basis of experimental results and then optimize it for the selection of these parameters within the given constraints in the end milling operation.3 MethodologyIn this work, mathematical models have been developed using experimental results with the help of response surface methodolog y. The purpose of developing mathematical models relating the machining responses and their factors is to facilitate the optimization of the machining process. This mathematical model has been used as an objective function and the optimization was carried out with the help of genetic algorithms.3.1 Mathematical formulationResponse surface methodology(RSM) is a combination of mathematical and statistical techniques useful for modelling and analyzing the problems in which several independent variables influence a dependent variable or response. The mathematical models commonly used are represented by:where Y is the machining response, ϕ is the response function and S, f , α, r are milling variables and ∈is the error which is normally distributed about the observed response Y with zero mean.The relationship between surface roughness and other independent variables can be represented as follows，where C is a constant and a, b, c and d are exponents.To facilitate the determination of constants and exponents, this mathematical model will have to be linearized by performing a logarithmic transformation as follows:The constants and exponents C, a, b, c and d can be determined by the method of least squares. The first order linear model, developed from the above functional relationship using least squares method, can be represented as follows:where Y1 is the estimated response based on the first-order equation, Y is the measured surface roughness on a logarithmic scale, x0 = 1 (dummy variable), x1, x2, x3 and x4 are logarithmic transformations of cutting speed, feed rate, radial rake angle and nose radiusrespectively, ∈is the experimental error and b values are the estimates of corresponding parameters.The general second order polynomial response is as given below:where Y2 is the estimated response based on the second order equation. The parameters, i.e. b0, b1, b2, b3, b4, b12, b23, b14, etc. are to be estimated by the method of least squares. Validity of the selected model used for optimizing the process parameters has been tested with the help of statistical tests, such as F-test, chi square test, etc. [10].3.2 Optimization using genetic algorithmsMost of the researchers have used traditional optimization techniques for solving machining problems. The traditional methods of optimization and search do not fare well over a broad spectrum of problem domains. Traditional techniques are not efficient when the practical search space is too large. These algorithms are not robust. They are inclined to obtain a local optimal solution. Numerous constraints and number of passes make the machining optimization problem more complicated. So, it was decided to employ genetic algorithms as an optimization technique. GA come under the class of non-traditional search and optimization techniques. GA are different from traditional optimization techniques in the following ways:1.GA work with a coding of the parameter set, not the parameter themselves.2.GA search from a population of points and not a single point.3.GA use information of fitness function, not derivatives or other auxiliary knowledge.4.GA use probabilistic transition rules not deterministic rules.5.It is very likely that the expected GA solution will be the global solution.Genetic algorithms (GA) form a class of adaptive heuristics based on principles derived from the dynamics of natural population genetics. The searching process simulates the natural evaluation of biological creatures and turns out to be an intelligent exploitation of a random search. The mechanics of a GA is simple, involving copying of binary strings. Simplicity of operation and computational efficiency are the two main attractions of the genetic algorithmic approach. The computations are carried out in three stages to get a result in one generation or iteration. The three stages are reproduction, crossover and mutation.In order to use GA to solve any problem, the variable is typically encoded into a string (binary coding) or chromosome structure which represents a possible solution to the given problem. GA begin with a population of strings (individuals) created at random. The fitness of each individual string is evaluated with respect to the given objective function. Then this initial population is operated on by three main operators – reproduction cross over and mutation– to create, hopefully, a better population. Highly fit individuals or solutions are given theopportunity to reproduce by exchanging pieces of their genetic information, in the crossover procedure, with other highly fit individuals. This produces new “offspring” solutions, which share some characteristics taken from both the parents. Mutation is often applied after crossover by altering some genes (i.e. bits) in the offspring. The offspring can either replace the whole population (generational approach) or replace less fit individuals (steady state approach). This new population is further evaluated and tested for some termination criteria. The reproduction-cross over mutation- evaluation cycle is repeated until the termination criteria are met.4 Experimental detailsFor developing models on the basis of experimental data, careful planning of experimentation is essential. The factors considered for experimentation and analysis were cutting speed, feed rate, radial rake angle and nose radius.4.1 Experimental designThe design of experimentation has a major affect on the number of experiments needed. Therefore it is essential to have a well designed set of experiments. The range of values of each factor was set at three different levels, namely low, medium and high as shown in Table 1. Based on this, a total number of 81 experiments (full factorial design), each having a combination of different levels of factors, as shown in Table 2, were carried out.The variables were coded by taking into account the capacity and limiting cutting conditions of the milling machine. The coded values of variables, to be used in Eqs. 3 and 4, were obtained from the following transforming equations:where x1 is the coded value of cutting speed (S), x2 is the coded value of the feed rate ( f ), x3 is the coded value of radial rake angle(α) and x4 is the coded value of nose radius (r).4.2 ExperimentationA high precision ‘Rambaudi Rammatic 500’ CNC milling machine, with a vertical milling head, was used for experimentation. The control system is a CNC FIDIA-12 compact. The cutting tools, used for the experimentation, were solid coated carbide end mill cutters of different radial rake angles and nose radii (WIDIA: DIA20 X FL38 X OAL 102 MM). The tools are coated with TiAlN coating. The hardness, density and transverse rupture strength are 1570 HV 30, 14.5 gm/cm3 and 3800 N/mm2 respectively.AISI 1045 steel specimens of 100×75 mm and 20 mm thickness were used in the present study. All the specimens were annealed, by holding them at 850 ◦C for one hour and then cooling them in a furnace. The chemical analysis of specimens is presented in Table 3. Thehardness of the workpiece material is 170 BHN. All the experiments were carried out at a constant axial depth of cut of 20 mm and a radial depth of cut of 1 mm. The surface roughness (response) was measured with Talysurf-6 at a 0.8 mm cut-off value. An average of four measurements was used as a response value.5 Results and discussionThe influences of cutting speed, feed rate, radial rake angle and nose radius have been assessed by conducting experiments. The variation of machining response with respect to the variables was shown graphically in Fig. 1. It is seen from these figures that of the four dependent parameters, radial rake angle has definite influence on the roughness of the surface machined using an end mill cutter. It is felt that the prominent influence of radial rake angle on the surface generation could be due to the fact that any change in the radial rake angle changes the sharpness of the cutting edge on the periphery, i.e changes the contact length between the chip and workpiece surface. Also it is evident from the plots that as the radial rake angle changes from 4◦to 16◦, the surface roughness decreases and then increases. Therefore, it may be concluded here that the radial rake angle in the range of 4◦to 10◦would give a better surface finish. Figure 1 also shows that the surface roughness decreases first and then increases with the increase in the nose radius. This shows that there is a scope for finding the optimum value of the radial rake angle and nose radius for obtaining the best possible quality of the surface. It was also found that the surface roughness decreases with an increase in cutting speed and increases as feed rate increases. It could also be observed that the surface roughness was a minimum at the 250 m/min speed, 200 mm/min feed rate, 10◦radial rake angle and 0.8 mm nose radius. In order to understand the process better, the experimental results can be used to develop mathematical models using RSM. In this work, a commercially available mathematical software package (MATLAB) was used for the computation of the regression of constants and exponents.5.1 The roughness modelUsing experimental results, empirical equations have been obtained to estimate surface roughness with the significant parameters considered for the experimentation i.e. cutting speed, feed rate, radial rake angle and nose radius. The first order model obtained from the above functional relationship using the RSM method is as follows:The transformed equation of surface roughness prediction is as follows:Equation 10 is derived from Eq. 9 by substituting the coded values of x1, x2, x3 and x4 in termsof ln s, ln f , lnαand ln r. The analysis of the variance (ANOV A) and the F-ratio test have been performed to justify the accuracy of the fit for the mathematical model. Since the calculated values of the F-ratio are less than the standard values of the F-ratio for surface roughness as shown in Table 4, the model is adequate at 99% confidence level to represent the relationship between the machining response and the considered machining parameters of the end milling process.The multiple regression coefficient of the first order model was found to be 0.5839. This shows that the first order model can explain the variation in surface roughness to the extent of 58.39%. As the first order model has low predictability, the second order model has been developed to see whether it can represent better or not.The second order surface roughness model thus developed is as given below:where Y2 is the estimated response of the surface roughness on a logarithmic scale, x1, x2, x3 and x4 are the logarithmic transformation of speed, feed, radial rake angle and nose radius. The data of analysis of variance for the second order surface roughness model is shown in Table 5.Since F cal is greater than F0.01, there is a definite relationship between the response variable and independent variable at 99% confidence level. The multiple regression coefficient of the second order model was found to be 0.9596. On the basis of the multiple regression coefficient (R2), it can be concluded that the second order model was adequate to represent this process. Hence the second order model was considered as an objective function for optimization using genetic algorithms. This second order model was also validated using the chi square test. The calculated chi square value of the model was 0.1493 and them tabulated value at χ2 0.005 is 52.34, as shown in Table 6, which indicates that 99.5% of the variability in surface roughness was explained by this model.Using the second order model, the surface roughness of the components produced by end milling can be estimated with reasonable accuracy. This model would be optimized using genetic algorithms (GA).5.2 The optimization of end millingOptimization of machining parameters not only increases the utility for machining economics, but also the product quality toa great extent. In this context an effort has been made to estimate the optimum tool geometry and machining conditions to produce the best possible surface quality within the constraints.The constrained optimization problem is stated as follows: Minimize Ra using the model given here:where xil and xiu are the upper and lower bounds of process variables xi and x1, x2, x3, x4 are logarithmic transformation of cutting speed, feed, radial rake angle and nose radius.The GA code was developed using MATLAB. This approach makes a binary coding system to represent the variables cutting speed (S), feed rate ( f ), radial rake angle (α) and nose radius (r), i.e. each of these variables is represented by a ten bit binary equivalent, limiting the total string length to 40. It is known as a chromosome. The variables are represented as genes (substrings) in the chromosome. The randomly generated 20 such chromosomes (population size is 20), fulfilling the constraints on the variables, are taken in each generation. The first generation is called the initial population. Once the coding of the variables has been done, then the actual decoded values for the variables are estimated using the following formula: where xi is the actual decoded value of the cutting speed, feed rate, radial rake angle and nose radius, x(L) i is the lower limit and x(U) i is the upper limit and li is the substring length, which is equal to ten in this case.Using the present generation of 20 chromosomes, fitness values are calculated by the following transformation:where f(x) is the fitness function and Ra is the objective function.Out of these 20 fitness values, four are chosen using the roulette-wheel selection scheme. The chromosomes corresponding to these four fitness values are taken as parents. Then the crossover and mutation reproduction methods are applied to generate 20 new chromosomes for the next generation. This processof generating the new population from the old population is called one generation. Many such generations are run till the maximum number of generations is met or the average of four selected fitness values in each generation becomes steady. This ensures that the optimization of all the variables (cutting speed, feed rate, radial rake angle and nose radius) is carried out simultaneously. The final statistics are displayed at the end of all iterations. In order to optimize the present problem using GA, the following parameters have been selected to obtain the best possible solution with the least computational effort: Table 7 shows some of the minimum values of the surface roughness predicted by the GA program with respect to input machining ranges, and Table 8 shows the optimum machining conditions for the corresponding minimum values of the surface roughness shown in Table 7. The MRR given in Table 8 was calculated bywhere f is the table feed (mm/min), aa is the axial depth of cut (20 mm) and ar is the radial depth of cut (1 mm).It can be concluded from the optimization results of the GA program that it is possible toselect a combination of cutting speed, feed rate, radial rake angle and nose radius for achieving the best possible surface finish giving a reasonably good material removal rate. This GA program provides optimum machining conditions for the corresponding given minimum values of the surface roughness. The application of the genetic algorithmic approach to obtain optimal machining conditions will be quite useful at the computer aided process planning (CAPP) stage in the production of high quality goods with tight tolerances by a variety of machining operations, and in the adaptive control of automated machine tools. With the known boundaries of surface roughness and machining conditions, machining could be performed with a relatively high rate of success with the selected machining conditions.6 ConclusionsThe investigations of this study indicate that the parameters cutting speed, feed, radial rake angle and nose radius are the primary actors influencing the surface roughness of medium carbon steel uring end milling. The approach presented in this paper provides n impetus to develop analytical models, based on experimental results for obtaining a surface roughness model using the response surface methodology. By incorporating the cutter geometry in the model, the validity of the model has been enhanced. The optimization of this model using genetic algorithms has resulted in a fairly useful method of obtaining machining parameters in order to obtain the best possible surface quality.中文翻译选择最佳工具，几何形状和切削条件利用表面粗糙度预测模型端铣摘要：刀具几何形状对工件表面质量产生的影响是人所共知的，因此，任何成型面端铣设计应包括刀具的几何形状。
淬硬齿轮的加工工艺
淬硬齿轮的加工工艺用于动力传动的齿轮和齿轮箱，其尺寸要求更小，齿轮传动的噪音更低，从而导致对淬硬齿轮的需求，也给齿轮制造厂家提出了探索齿轮加工新方法的要求。
齿轮在淬硬热处理过程中，其材料组织及应力的改变，通常会使齿轮产生变形，即齿形、齿向及齿距误差。
这此误差将引起齿廓在传动时的不正确啮合，从而加大了载荷，产生齿轮噪音。
因此，淬硬齿轮在热处理后，一般应添加一道精加工工序。
淬硬齿轮精加工工艺可分为两类：一类是采用非成形的切削刃，如齿轮磨削加工；另一类则是具有成形的切削刃如淬硬齿轮(HRC48～53)滚削加工。
用于硬滚齿加工的硬质合金刀具成形切削刃的精加工过程。
当今的硬质合金材料、刀具涂层和滚齿机技术的发展，已使淬硬齿轮滚切加工技术有了显著的提高，特别是在加工小于或等于12DP的中小模数齿轮时，可承受硬切削过程中所产生的极大的切削力。
硬质合金滚刀的选取硬质合金滚刀在材料的品种规格上有很大进展。
超细、细、中等或大颗粒的硬质合金现在都有产品。
此外，硬质合金滚刀毛坯的成形工艺技术也有了显著提高，如采用热等静压(HIP)工艺，该工艺在高压高温下，增加了硬质合金毛坯的内在结合力，提高了硬质合金的抗弯强度。
按照ISO的规定，实体硬质合金材料可按应用场合的不同分为若干类：齿轮切削刀具分为K类和P类，K类硬质合金有更高的耐磨性，P类则有更好的高温红硬性。
在K牌号和P牌号硬质合金中，每种牌号硬质合金的颗粒结构是不同的，从中等颗粒到超细颗粒。
每种牌号都有其应用场合，这是和颗粒结构相关联的。
一般来说，对于软滚削，K类比P类的性能要好，K类硬质合金能得到微米级的颗粒结构(粒度小于0.5μm)，而P类则不行。
在磨耗方面，K类韧性更好，寿命更长。
滚刀的重新刃磨和翻新滚刀加工一定数量的工件后，其切削刃变钝，此时必须重新刃磨。
刃磨后的滚刀必须保持原有的几何形状；切削刃必须锋利；刀具的金相结构绝不可因磨削过热而受破坏。
因而在刃磨硬质合金滚刀时应采用一种油基冷却液，它对氯和硫不起反应。
毕业论文外文翻译-齿轮的加工方法
英文原文Gear manufacturing methodsThere are two basic methods of manufacturing gear teeth: the generating process and the forming process. when a gear tooth is generated, the workpiece and the cutting or grinding tool are in continuous mesh and the tooth form is generated by the tool. In other words, the work and the tool are conjugated to each other. hobbing :machines, shaper cutters, shaving machines, and grinders use this principle.When a gear tooth is formed, the tool is in the shape of the space that is being machined out. Some grinding machines use this principle with an indexing mechianism which allows the gear teeth to be formed tooth by tooth. Broaches are examples of form tools that machine all the gear teeth simultaneously.shapingShaping is inherently similar to planning but uses a circular cuttrer instead of rack and the resulting reduction in the reciprocating inertia allows much higher stroking speeds: modern shapers cutting car gears can run at 2,000 cutting strokes per minmute. The shape of the cutter is roughly the same as an involute gear but the tips of the teeth are rounded.The generating drive between cutter and workpiece does not involve a rack or leadscrew since only circular motion in involved. The tool and workpiece move tangential typically 0.5 mm for each stroke of the cutter. On the return stroke the cutter must be retracted about 1 mm to give clearance otherwise tool rub occurs on the backstroke and failure is rapid. The speed on this type of machine is limited by the rate at which some 50kg of cutter and bearings can be moved a distance of 1 mm. the accelerations involved tequire forces of the order of 5000N yet high accuracy must be maintained.The advantages of shaping are that production rates are relatively high and that it is possible to cut right up to a shoulder. Unfortunately, for helical gears, a helical guide is required to impose a rotational motion on the stroking motion; such helical guides cannot be produced easily or cheaply so the method is only suitable for long runs with helical gears since special cutters and guides must be manufactured for each different helix angle. A great advantage of shaping is its ability to annular gears such as those required for large epicyclie drives.When very high accuracy is of importance the inaccuracies in the shaping cutter matter since they may transfer to the cut gear. It is obvious that profile errors will transfer but it is less obvious than an eccentrically mounted or ground cutter will give a characteristic “dropped tooth”. There are several causes for “dropped tooth” but it occurs most commonly when the diameter of the workpiece is about half, one and half, two and a half, etc, times the cutter diameter. If the cutter starts on a high point and finishes on a low point during the final finishing revolution of the gear the peak to peak eccentricity errors in the cutter occurs between the last and the first tooth of the final revolution of the cut gear; as the cumulative pitch error of the cutter may well be over 25 microns there is a sudden pitch error of this amount on the cut gear. The next gear cut on the machine may however be very good on adjacent pitch if the final cut happened to start in a favorable position on the cutter.Various attempts have been made to prevent this effect, in particular by continuing rotation without any further cutter infeed but if the shaping machine is not very rigid and the cutter very sharp then no further cutting will occur and the error will not be removed.hobbinghobbing, the most used metal cutting method, uses the rack generating principle but avoids slow reciprocation by mounting many “racks ” on a rotating cutter. The “racks” are displaced axially to form a gashed worm. The “racks” do not generate the correct involute shape for the whole length of the teeth since they are moving on a circular path and so the hob is fed slowly along the teeth either axially in normal or in the direction of the helix in “oblique” hobbing.Metal removal rates are high since no reciprocation of hob or workpiece is required and so cutting speeds of 40 m/min can be used for conventional hobs and up to 150m/min for carbide hobs. Typically with a 100mm diameter hob the rotation speed will be 100rpm and so a twenty tooth workpiece will rotate at 5 rpm. Each revolution of the workpiece will correspond to 0.75mm feed so the hob will advance through the workpiece at about 4mm per minute. For car production roughing multiple start hobs can be used with coarse feeds of 3mm per revolution so that 100 rpm on the cutter, a two-start hob and a 20 tooth gear will give a feed rate of 30mm/minute.The disadvantage of a coarse feed rate is that a clear marking is left on the workpiece, particularly in the root, showing a pattern at a spacing of the feed rate per revolution. This surface undulation is less marked on the flanks than in the root and is not important when there is a subsequent finishing operation such as shaving or grinding. When there are no further operations the feed per revolution must be restricted to keep the undulations below a limit which is usually dictated by lubrication conditions. The height of the undulations in the root of the gear is given by squaring the feed per revolution and dividing by four times the diameter of the hob; 1 mm feed and 100mm diameter gives 2.5 micron high undulations in the root. On the gear flank the undulation is roughly cos70 as large, i.e., about 0.85 micron.Accuracy of hobbing is normally high for pitch and for helix, provided machines are maintained; involute is dependent solely on the accuracy of the hob profile. As the involute form is generated by as many cuts as there are gashes on the hob the involute is not exact, but if there are, say, 14 tangents generating a flank of 20 mm radius curvature about 4 mm high the divergence from a true involute is only about half a micron; hob manufacturing and mounting errors can be above 10 microns. Use of twostart hobs or oblique hobbing gives increased error levels since hob errors of pitching transfer to the cut gear.broachingBroaching is not used for helical gears but is useful for internal spur gears; the principal use of broaching in this context is for internal splines which cannot easily be made by any other method. As with all broaching the method is only economic for large quantities since setup costs are high.The major application of broaching techniques to helical external gears is that used by Gleasons in their G-TRAC machine .this machine operates by increasing the effective radius of a hobbing cutter to infinity so that each tooth of the cutter is travelingin a straight line instead of on a radius. This allows the cutting action to extend over the whole facewidth of a gear instead of the typical 0.75 mm feed per revolution of hobbing. The resulting process gives a very high production rate , more suitable for U.S.A. production volumes than for the relatively low European volumes and so, despite a high initial cost ,is very competitive.Broaching give high accuracy and good surface finish but like all cutting processes is limited to “soft” materials which must be subsequently casehardened or heat treated, giving distortion.ShavingA shaving cutting cutter looks like a gear which has extra clearance at the root and whose tooth flanks have been grooved to give cutting edges. It is run in mesh with the rough gear with crossed axes so that there is in theory point contact with a relative velocity along the teeth giving scraping action. The shaving cutter teeth are relatively flexible in bending and so will only operate effectively when they are in double contact between two gear teeth. The gear and cutter operate at high rotational speeds with traversing of the workface and about 100 mm micron of material is removed. Cycle times can be less than half a minute and the machines are not expensive but cutters are delicate and difficult to manufacture. It is easy to make adjustments of profile at the shaving stage and crowning can be applied. Shaving can be carried out near a shoulder by using a cutter which is plunged in to depth without axial movement; this method is fast but requires more complex cutter design.grindingGrinding is extremely important because it is the main way hardened gear are machined. When high accuracy is required it is not sufficient to pre-correct for heat treatment distortion and grinding is then necessary.The simplest approach to grinding, often termed the Orcutt method. The wheel profile is dressed accurately to shape using single point diamonds which are controlled by templates cut to the exact shape required; 6:1 scaling with a pantograph is often used. The profile wheel is then reciprocated axially along the gear which rotates to allow for helix angle effects; when one tooth shape has been finished, involving typically 100 micron metal removal the gear is indexed to the next tooth space. This method is fairly show but gives high accuracy consistently. Setting up is lengthy because different dressing templates are needed if module, number of teeth, helix angle, or profile correction are changed.The fastest grinding method uses the same principle as hobbing but replaces a gashed and relieved worm by a grinding wheel which is a rack in section. Since high surface speeds are needed the wheel diameter is increased so that wheels of 0.5 m diameter can run at over 2000 rpm to give the necessary 1000 m/min. only single start worms are cut on the wheel but gear rotation speeds are high,100 rpm typically, so it is difficult to design the drive system to give accuracy and rigidity. Accuracy of the process is reasonably high although there is a tendency for wheel and workpiece to deflect variably during grinding so the wheel form may require compensation for machine deflection effects. Generation of a worm shape on the grinding wheel is a slow process since a dressing diamond or roller must not only form the rack profile but has to move axially as the wheel rotates. Once the wheel has been trued, gears can be groundrapidly until redressing is required. This is the most popular method for high production rates with small gear and is usually called the Reishauer method.Large gears are usually generated by the Maag method which is similar to planning in its approach but uses cup grinding wheels of large diameter to form the flanks of the theoretical mating rack. Gears of very large diameter cannot easily be moved so the gear is essentially stationary while the grinding wheel carriage reciprocates in the direction of the helix. The wheel is only in contact over a small part of the facewidth in helical gears so this is not important when only a few gears of this size are made in a year. As with form grinding, after grinding a pair of flanks the gear is indexed to the next pair.A similar method used for medium size gears has stationary wheels, while the rough gear is traversed under the wheels. Corresponding rotational movement of the gear is controlled by steel bands unwrapping from a cylinder of pitch circle diameter so that the motion of gear relative to “rack” is correct.Another method, the Nile approach, uses a wheel which is formed to give the “theoretical mating rack” instead of using two cup wheels as in the Maag method. This approach is best suited to medium precision work on smaller gears and is intermediate in speed between the Reishauer and Maag methods.All grinding processes are slow and costly compared with cutting processed and so are only used when accuracy is essential. A rough rule of thumb is that grinding will increase gear cutting costs by a factor of 10 but the cost of the teeth is often only a small part of the total cost of a gearbox. The accuracies attainable are surprisingly not very dependent on size of gear ; whether a gear is 5 m or 50 m diameter the pitch involute and helix accuracies attainable are of the order of 5 microns or better and more dependent on the skill and patience of the operator and inspectors than on any other factors.It is often assumed that grinding will remove all error generated at the roughing stage. Unfortunately, grinding machines are relatively flexible and so the grinding wheel has a tendency to follow previous errors. The errors will thus be reduced but not completely eliminated unless very many cuts are used; whenever a grinding process is giving in consistent results it is advisable to check the accuracies at the rough-cut stage. The only exception is the form grinding process which will not follow involute errors though it will still allow helix and pitch errors.中文译文齿轮的加工方法加工齿轮轮齿有两种基本的方法：产生过程和形成过程。
机械制造 毕业设计 外文英文文献 翻译 齿轮和齿轮传动
机械制造毕业设计外文英文文献翻译齿轮和齿轮传动Gears and gear driveGears are the most durable and rugged of all mechanical drives. They can transmit high power at efficiencies up to 98% and with long service lives. For this reason, gears rather than belts or chains are found in automotive transmissions and most heavy-duty machine drives. On the other hand, gears are more expensive than other drives, especially if they are machined and not made from power metal or plastic.Gear cost increases sharply with demands for high precision and accuracy. So it is important to establish tolerance requirements appropriate for the application. Gears that transmit heavy loads or than operate at high speeds are not particularly expensive, but gears that must do both are costly.Silent gears also are expensive. Instrument and computer gears tend to be costly because speed or displacement ratios must be exact. At the other extreme, gears operating at low speed in exposed locations are normally termed no critical and are made to minimum quality standards.For tooth forms, size, and quality, industrial practice is to follow standards set up by the American Gear Manufactures AssociationAGMA.Tooth formStandards published by AGMA establish gear proportions and tooth profiles. Tooth geometry is determined primarily by pitch, depth, and pressure angle.Pitch：Standards pitches are usually whole numbers when measured as diametral pitch P. Coarse-pitch gearing has teeth larger than 20 diametral pitch ?usually 0.5 to 19.99. Fine-pitch gearing usually has teeth of diametral pitch 20 to 200.Depth: Standardized in terms of pitch. Standard full-depth have working depth of 2/p. If the teeth have equal addendaas in standard interchangeable gears the addendum is 1/p. Stub teeth have a working depth usually 20% less than full-depth teeth. Full-depth teeth have a larger contract ratio than stub teeth. Gears with small numbers of teeth may have undercut so than they do not interfere with one another during engagement. Undercutting reduce active profile and weakens the tooth.Mating gears with long and short addendum have larger load-carrying capacity than standard gears. The addendum of the smaller gear pinion is increased while that of larger gear is decreased, leaving the whole depth the same. This form is know as recess-action gearing.Pressure Angle: Standard angles are and . Earlier standards include a 14-pressure angle that is still used. Pressure angle affectsthe force that tends to separate mating gears. High pressure angle decreases the contact ratio ratio of the number of teeth in contact but provides a tooth of higher capacity and allows gears to have fewer teeth without undercutting.Backlash: Shortest distances between the non-contacting surfaces of adjacent teeth .Gears are commonly specified according to AGMA Class Number, which is a code denoting important quality characteristics. Quality number denote tooth-element tolerances. The higher the number, the closer the tolerance. Number 8 to 16 apply to fine-pitch gearing.Gears are heat-treated by case-hardening, through-hardening, nitriding, or precipitation hardening. In general, harder gears are stronger and last longer than soft ones. Thus, hardening is a device that cuts the weight and size of gears. Some processes, such as flame-hardening, improve service life but do not necessarily improve strength.Design checklistThe larger in a pair is called the gear, the smaller is called the pinion.Gear Ratio: The number of teeth in the gear divide by the number of teeth in the pinion. Also, ratio of the speed of the pinion to the speed of the gear. In reduction gears, the ratio of input to output speeds.Gear Efficiency: Ratio of output power to input power. includesconsideration of power losses in the gears, in bearings, and from windage and churning of lubricant.Speed: In a given gear normally limited to some specific pitchline velocity. Speed capabilities can be increased by improving accuracy of the gear teeth and by improving balance of the rotating parts.Power: Load and speed capacity is determined by gear dimensions and by type of gear. Helical and helical-type gears have the greatest capacity to approximately 30,000 hp. Spiral bevel gear are normally limited to 5,000 hp, and worm gears are usually limited to about 750 hp.Special requirementsMatched-Set Gearing: In applications requiring extremely high accuracy, it may be necessary to match pinion and gear profiles and leads so that mismatch does not exceed the tolerance on profile or lead for the intended application.Tooth Spacing: Some gears require high accuracy in the circular of teeth. Thus, specification of pitch may be required in addition to an accuracy class specification.Backlash: The AMGA standards recommend backlash ranges to provide proper running clearances for mating gears. An overly tight mesh may produce overload. However, zero backlash is required in some applications.Quiet Gears: To make gears as quit as possible, specify thefinest pitch allowable for load conditions. In some instances, however, pitch is coarsened to change mesh frequency to produce a more pleasant, lower-pitch sound. Use a low pressure angle. Use a modified profile to include root and tip relief. Allow enough backlash. Use high quality numbers. Specify a surface finish of 20 in. or better. Balance the gear set. Use a nonintegral ratio so that the same teeth do not repeatedly engage if both gear and pinion are hardened steel. If the gear is made of a soft material, an integral ratio allows the gear to cold-work and conform to the pinion, thereby promoting quiet operation. Make sure critical are at least 20% apart from operating speeding or speed multiples and from frequency of tooth mesh.Multiple mesh gearMultiple mesh refers to move than one pair of gear operating in a train. Can be on parallel or nonparallel axes and on intersection or nonintersecting shafts. They permit higer speed ratios than are feasible with a single pair of gears .Series trains:Overall ratio is input shaft speed divided by output speed ,also the product of individual ratios at each mesh ,except in planetary gears .Ratio is most easily found by dividing the product of numbers of teeth of driven gears by the product of numbers of teeth of driving gears.Speed increasers with step-up rather than step-down ratios mayrequire special care in manufacturing and design. They often involve high speeds and may creste problems in gear dynamics. Also, frictional and drag forces are magnified which, in extreme cases , may lead to operational problems.Epicyclic Gearing:Normally, a gear axis remains fixed and only the gears rotates. But in an epicyclic gear train, various gears axes rotate about one anther to provide specialized output motions. With suitable clutchse and brakes, an epicyclic train serves as the planetary gear commonly found in automatic transmissions.Epicyclic trains may use spur or helical gears, external or internal, or bevel gears. In transmissions, the epicyclic or planetary gears usually have multiple planets to increase load capacity.In most cases, improved kinematic accuracy in a gearset decreases gear mesh excitation and results in lower drive noise. Gearset accuracy can be increased by modifying the tooth involute profile, by substituting higher quality gearing with tighter manufacturing tolerances, and by improving tooth surface finish. However, if gear mesh excitation generaters resonance somewhere in the drive system, nothing short of a “perfect” gearset will substantially reduce vibration and noise.Tooth profiles are modified to avoid interferences which can result from deflections in the gears, shafts, and housing as teeth engageand disendgage. If these tooth interferences are not compensated for by profile modifications, gears load capacity can be seriously reduced. In addition, the drive will be noisier because tooth interferences generate high dynamic loads. Interferences typically are eliminated by reliving the tooth tip, the tooth flank, or both. Such profile modifications are especially important for high-load , high-speed drives. The graph of sound pressure levelvs tip relief illustrates how tooth profile modifications can affect overall drive noise. If the tip relief is less than this optimum value, drive noise increases because of greater tooth interference; a greater amount of tip relief also increase noise because the contact ratio is decreased.Tighter manufacturing tolerances also produce quietier gears. Tolerances for such parameters as profile error, pitch AGMA quality level. For instance, the graph depicting SPL vs both speed and gear quality shows how noise decreases example, noise is reduced significantly by an increase in accuracy from an AGMA Qn 11 quality to an AGNA Qn 15 quality. However, for most commercial drive applications, it is doubtful that the resulting substantial cost increase for such an accuracy improvement can be justified simply on the basis of reduced drive noise.Previously, it was mentioned that gears must have adequate clearance when loaded to prevent tooth interference during the course of meshing. Tip and flank relief are common profile modifications thatcontrol such interference. Gears also require adequate backlash and root clearance. Noise considerations make backlash an important parameter to evaluate during drive design. Sufficient backlash must be provided under all load and temperature conditions to avoid a tight mesh, which creates excessively high noise level. A tight mesh due to insufficient backlash occurs when the drive and coast side of a tooth are in contact simultaneously. On the other hand, gears with excessive backlash also are noisy because of impacting teeth during periods of no load or reversing load. Adequate backlash should be provided by tooth thinning rather than by increase in center distance. Tooth thinning dose not decrease the contact ratio, whereas an increase in center distance does. However, tooth thinning does reduce the bending fatigue, a reduction which is small for most gearing systems.齿轮和齿轮传动在所有的机械传动形式中，齿轮传动是一种最结实耐用的传动方式。
机械加工外文翻译
附录附录1英文原文Basic Machining Operations and Cutting TechnologyBasic Machining OperationsMachine tools have evolved from the early foot-powered lathes of the Egyptians and John Wilkinson's boring mill. They are designed to provide rigid support for both the work piece and the cutting tool and can precisely control their relative positions and the velocity of the tool with respect to the work piece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile work piece in the form of a severely deformed chip. The chip is a waste product that is considerably shorter than the work piece from which it came but with a corresponding increase in thickness of the uncut chip. The geometrical shape of work piece depends on the shape of the tool and its path during the machining operation.Most machining operations produce parts of differing geometry. If a rough cylindrical work piece revolves about a central axis and the tool penetrates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. If a hollow tube is machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning, if the tool point travels in a path of varying radius, a contoured surface like that of a bowling pin can be produced; or, if the piece is short enough and the support is sufficiently rigid, a contoured surface could be produced by feeding a shaped tool normal to the axis of rotation. Short tapered or cylindrical surfaces could also be contour formed.Flat or plane surfaces are frequently required. They can be generated by radial turning or facing, in which the tool point moves normal to the axis of rotation. In other cases, it is more convenient to hold the work piece steady and reciprocate the tool across it in a series of straight-line cuts with a crosswise feed increment before each cutting stroke. This operation is called planning and is carried out on a shaper. For larger pieces it is easier to keep the tool stationary and draw the work piece under it as in planning. The tool is fed at each reciprocation. Contoured surfaces can be produced by using shaped tools.Multiple-edged tools can also be used. Drilling uses a twin-edged fluted tool for holes with depths up to 5 to 10 times the drill diameter. Whether thedrill turns or the work piece rotates, relative motion between the cutting edge and the work piece is the important factor. In milling operations a rotary cutter with a number of cutting edges engages the work piece. Which moves slowly with respect to the cutter. Plane or contoured surfaces may be produced, depending on the geometry of the cutter and the type of feed. Horizontal or vertical axes of rotation may be used, and the feed of the work piece may be in any of the three coordinate directions.Basic Machine ToolsMachine tools are used to produce a part of a specified geometrical shape and precise I size by removing metal from a ductile material in the form of chips. The latter are a waste product and vary from long continuous ribbons of a ductile material such as steel, which are undesirable from a disposal point of view, to easily handled well-broken chips resulting from cast iron. Machine tools perform five basic metal-removal processes: I turning, planning, drilling, milling, and grinding. All other metal-removal processes are modifications of these five basic processes. For example, boring is internal turning; reaming, tapping, and counter boring modify drilled holes and are related to drilling; bobbing and gear cutting are fundamentally milling operations; hack sawing and broaching are a form of planning and honing; lapping, super finishing. Polishing and buffing are variants of grinding or abrasive removal operations. Therefore, there are only four types of basic machine tools, which use cutting tools of specific controllable geometry: 1. lathes, 2. planers, 3. drilling machines, and 4. milling machines. The grinding process forms chips, but the geometry of the abrasive grain is uncontrollable.The amount and rate of material removed by the various machining processes may be I large, as in heavy turning operations, or extremely small, as in lapping or super finishing operations where only the high spots of a surface are removed.A machine tool performs three major functions: 1. it rigidly supports the work piece or its holder and the cutting tool; 2. it provides relative motion between the work piece and the cutting tool; 3. it provides a range of feeds and speeds usually ranging from 4 to 32 choices in each case.Speed and Feeds in MachiningSpeeds, feeds, and depth of cut are the three major variables for economical machining. Other variables are the work and tool materials, coolant and geometry of the cutting tool. The rate of metal removal and power required for machining depend upon these variables.The depth of cut, feed, and cutting speed are machine settings that must be established in any metal-cutting operation. They all affect the forces, the power, and the rate of metal removal. They can be defined by comparing them to the needle and record of a phonograph. The cutting speed (V) is represented by the velocity of- the record surface relative to the needle in the tone arm at any instant. Feed is represented by the advance of the needle radially inward perrevolution, or is the difference in position between two adjacent grooves. The depth of cut is the penetration of the needle into the record or the depth of the grooves.Turning on Lathe CentersThe basic operations performed on an engine lathe are illustrated. Those operations performed on external surfaces with a single point cutting tool are called turning. Except for drilling, reaming, and lapping, the operations on internal surfaces are also performed by a single point cutting tool.All machining operations, including turning and boring, can be classified as roughing, finishing, or semi-finishing. The objective of a roughing operation is to remove the bulk of the material as rapidly and as efficiently as possible, while leaving a small amount of material on the work-piece for the finishing operation. Finishing operations are performed to obtain the final size, shape, and surface finish on the work piece. Sometimes a semi-finishing operation will precede the finishing operation to leave a small predetermined and uniform amount of stock on the work-piece to be removed by the finishing operation.Generally, longer work pieces are turned while supported on one or two lathe centers. Cone shaped holes, called center holes, which fit the lathe centers are drilled in the ends of the work piece-usually along the axis of the cylindrical part. The end of the work piece adjacent to the tail stock is always supported by a tail stock center, while the end near the head stock may be supported by a head stock center or held in a chuck. The head stock end of the work piece may be held in a four-jaw chuck, or in a type chuck. This method holds the work piece firmly and transfers the power to the work piece smoothly; the additional support to the work piece provided by the chuck lessens the tendency for chatter to occur when cutting. Precise results can be obtained with this method if care is taken to hold the work piece accurately in the chuck.Very precise results can be obtained by supporting the work piece between two centers. A lathe dog is clamped to the work piece; together they are driven by a driver plate mounted on the spindle nose. One end of the Work piece is mecained;then the work piece can be turned around in the lathe to machine the other end. The center holes in the work piece serve as precise locating surfaces as well as bearing surfaces to carry the weight of the work piece and to resist the cutting forces. After the work piece has been removed from the lathe for any reason, the center holes will accurately align the work piece back in the lathe or in another lathe, or in a cylindrical grinding machine. The work piece must never be held at the head stock end by both a chuck and a lathe center. While at first thought this seems like a quick method of aligning the work piece in the chuck, this must not be done because it is not possible to press evenly with the jaws against the work piece while it is also supported by the center. The alignment provided by the center will not be maintained and the pressure of the jaws may damage the center hole, the lathe center, andperhaps even the lathe spindle. Compensating or floating jaw chucks used almost exclusively on high production work provide an exception to the statements made above. These chucks are really work drivers and cannot be used for the same purpose as ordinary three or four-jaw chucks.While very large diameter work pieces are sometimes mounted on two centers, they are preferably held at the headstock end by faceplate jaws to obtain the smooth power transmission; moreover, large lathe dogs that are adequate to transmit the power not generally available, although they can be made as a special. Faceplate jaws are like chuck jaws except that they are mounted on a faceplate, which has less overhang from the spindle bearings than a large chuck would have.Introduction of MachiningMachining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported work piece.Low setup cost for small Quantities. Machining has two applications in manufacturing. For casting, forging, and press working, each specific shape to be produced, even one part, nearly always has a high tooling cost. The shapes that may he produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, by machining; to start with nearly any form of raw material, so tong as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore .machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or press working if a high quantity were to be produced.Close accuracies, good finishes. The second application for machining is based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in press worked parts may be machined following the press working operations.Primary Cutting ParametersThe basic tool-work relationship in cutting is adequately described by means of four factors: tool geometry, cutting speed, feed, and depth of cut.The cutting tool must be made of an appropriate material; it must be strong, tough, hard, and wear resistant. The tool s geometry characterized by planes and angles, must be correct for each cutting operation. Cutting speed is the rate at which the work surface passes by the cutting edge. It may be expressed in feet per minute.For efficient machining the cutting speed must be of a magnitude appropriate to the particular work-tool combination. In general, the harder the work material, the slower the speed.Feed is the rate at which the cutting tool advances into the work piece. "Where the work piece or the tool rotates, feed is measured in inches per revolution. When the tool or the work reciprocates, feed is measured in inches per stroke, Generally, feed varies inversely with cutting speed for otherwise similar conditions.The depth of cut, measured inches is the distance the tool is set into the work. It is the width of the chip in turning or the thickness of the chip in a rectilinear cut. In roughing operations, the depth of cut can be larger than for finishing operations.The Effect of Changes in Cutting Parameters on Cutting TemperaturesIn metal cutting operations heat is generated in the primary and secondary deformation zones and these results in a complex temperature distribution throughout the tool, work piece and chip. A typical set of isotherms is shown in figure where it can be seen that, as could be expected, there is a very large temperature gradient throughout the width of the chip as the work piece material is sheared in primary deformation and there is a further large temperature in the chip adjacent to the face as the chip is sheared in secondary deformation. This leads to a maximum cutting temperature a short distance up the face from the cutting edge and a small distance into the chip.Since virtually all the work done in metal cutting is converted into heat, it could be expected that factors which increase the power consumed per unit volume of metal removed will increase the cutting temperature. Thus an increase in the rake angle, all other parameters remaining constant, will reduce the power per unit volume of metal removed and the cutting temperatures will reduce. When considering increase in unreformed chip thickness and cutting speed the situation is more complex. An increase in undeformed chip thickness tends to be a scale effect where the amounts of heat which pass to the work piece, the tool and chip remain in fixed proportions and the changes in cutting temperature tend to be small. Increase in cutting speed; however, reduce the amount of heat which passes into the work piece and this increase the temperature rise of the chip m primary deformation. Further, the secondary deformation zone tends to be smaller and this has the effect of increasing the temperatures in this zone. Other changes in cutting parameters have virtually no effect on the power consumed per unit volume of metal removed and consequently have virtually no effect on the cutting temperatures. Since ithas been shown that even small changes in cutting temperature have a significant effect on tool wear rate it is appropriate to indicate how cutting temperatures can be assessed from cutting data.The most direct and accurate method for measuring temperatures in high -speed-steel cutting tools is that of Wright &. Trent which also yields detailed information on temperature distributions in high-speed-steel cutting tools. The technique is based on the metallographic examination of sectioned high-speed-steel tools which relates microstructure changes to thermal history.Trent has described measurements of cutting temperatures and temperature distributions for high-speed-steel tools when machining a wide range of work piece materials. This technique has been further developed by using scanning electron microscopy to study fine-scale microstructure changes arising from over tempering of the tempered martens tic matrix of various high-speed-steels. This technique has also been used to study temperature distributions in both high-speed -steel single point turning tools and twist drills.Wears of Cutting ToolDiscounting brittle fracture and edge chipping, which have already been dealt with, tool wear is basically of three types. Flank wear, crater wear, and notch wear. Flank wear occurs on both the major and the minor cutting edges. On the major cutting edge, which is responsible for bulk metal removal, these results in increased cutting forces and higher temperatures which if left unchecked can lead to vibration of the tool and work piece and a condition where efficient cutting can no longer take place. On the minor cutting edge, which determines work piece size and surface finish, flank wear can result in an oversized product which has poor surface finish. Under most practical cutting conditions, the tool will fail due to major flank wear before the minor flank wear is sufficiently large to result in the manufacture of an unacceptable component.Because of the stress distribution on the tool face, the frictional stress in the region of sliding contact between the chip and the face is at a maximum at the start of the sliding contact region and is zero at the end. Thus abrasive wear takes place in this region with more wear taking place adjacent to the seizure region than adjacent to the point at which the chip loses contact with the face. This result in localized pitting of the tool face some distance up the face which is usually referred to as catering and which normally has a section in the form of a circular arc. In many respects and for practical cutting conditions, crater wear is a less severe form of wear than flank wear and consequently flank wear is a more common tool failure criterion. However, since various authors have shown that the temperature on the face increases more rapidly with increasing cutting speed than the temperature on the flank, and since the rate of wear of any type is significantly affected by changes in temperature, crater wear usually occurs at high cutting speeds.At the end of the major flank wear land where the tool is in contact with the uncut work piece surface it is common for the flank wear to be more pronounced than along the rest of the wear land. This is because of localised effects such as a hardened layer on the uncut surface caused by work hardening introduced by a previous cut, an oxide scale, and localised high temperatures resulting from the edge effect. This localised wear is usually referred to as notch wear and occasionally is very severe. Although the presence of the notch will not significantly affect the cutting properties of the tool, the notch is often relatively deep and if cutting were to continue there would be a good chance that the tool would fracture.If any form of progressive wear allowed to continue, dramatically and the tool would fail catastrophically, i. e. the tool would be no longer capable of cutting and, at best, the work piece would be scrapped whilst, at worst, damage could be caused to the machine tool. For carbide cutting tools and for all types of wear, the tool is said to have reached the end of its useful life long before the onset of catastrophic failure. For high-speed-steel cutting tools, however, where the wear tends to be non-uniform it has been found that the most meaningful and reproducible results can be obtained when the wear is allowed to continue to the onset of catastrophic failure even though, of course, in practice a cutting time far less than that to failure would be used. The onset of catastrophic failure is characterized by one of several phenomena, the most common being a sudden increase in cutting force, the presence of burnished rings on the work piece, and a significant increase in the noise level.Mechanism of Surface Finish ProductionThere are basically five mechanisms which contribute to the production of a surface which have been machined. These are:(l) The basic geometry of the cutting process. In, for example, single point turning the tool will advance a constant distance axially per revolution of the workpiecc and the resultant surface will have on it, when viewed perpendicularly to the direction of tool feed motion, a series of cusps which will have a basic form which replicates the shape of the tool in cut.(2) The efficiency of the cutting operation. It has already been mentioned that cutting with unstable built-up-edges will produce a surface which contains hard built-up-edge fragments which will result in a degradation of the surface finish. It can also be demonstrated that cutting under adverse conditions such as apply when using large feeds small rake angles and low cutting speeds, besides producing conditions which lead to unstable built-up-edge production, the cutting process itself can become unstable and instead of continuous shear occurring in the shear zone, tearing takes place, discontinuous chips of uneven thickness are produced, and the resultant surface is poor. This situation is particularly noticeable when machining very ductile materials such as copper and aluminum.(3) The stability of the machine tool. Under some combinations of cutting conditions; work piece size, method of clamping ,and cutting tool rigidity relative to the machine tool structure, instability can be set up in the tool which causes it to vibrate. Under some conditions this vibration will reach and maintain steady amplitude whilst under other conditions the vibration will built up and unless cutting is stopped considerable damage to both the cutting tool and work piece may occur. This phenomenon is known as chatter and in axial turning is characterized by long pitch helical bands on the work piece surface and short pitch undulations on the transient machined surface.(4)The effectiveness of removing swarf. In discontinuous chip production machining, such as milling or turning of brittle materials, it is expected that the chip (swarf) will leave the cutting zone either under gravity or with the assistance of a jet of cutting fluid and that they will not influence the cut surface in any way. However, when continuous chip production is evident, unless steps are taken to control the swarf it is likely that it will impinge on the cut surface and mark it. Inevitably, this marking besides looking.(5)The effective clearance angle on the cutting tool. For certain geometries of minor cutting edge relief and clearance angles it is possible to cut on the major cutting edge and burnish on the minor cutting edge. This can produce a good surface finish but, of course, it is strictly a combination of metal cutting and metal forming and is not to be recommended as a practical cutting method. However, due to cutting tool wear, these conditions occasionally arise and lead to a marked change in the surface characteristics.Limits and TolerancesMachine parts are manufactured so they are interchangeable. In other words, each part of a machine or mechanism is made to a certain size and shape so will fit into any other machine or mechanism of the same type. To make the part interchangeable, each individual part must be made to a size that will fit the mating part in the correct way. It is not only impossible, but also impractical to make many parts to an exact size. This is because machines are not perfect, and the tools become worn. A slight variation from the exact size is always allowed. The amount of this variation depends on the kind of part being manufactured. For examples part might be made 6 in. long with a variation allowed of 0.003 (three-thousandths) in. above and below this size. Therefore, the part could be 5.997 to 6.003 in. and still be the correct size. These are known as the limits. The difference between upper and lower limits is called the tolerance.A tolerance is the total permissible variation in the size of a part.The basic size is that size from which limits of size arc derived by the application of allowances and tolerances.Sometimes the limit is allowed in only one direction. This is known as unilateral tolerance.Unilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is shown in only one direction from the nominal size. Unilateral tolerancing allow the changing of tolerance on a hole or shaft without seriously affecting the fit.When the tolerance is in both directions from the basic size it is known as a bilateral tolerance (plus and minus).Bilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is split and is shown on either side of the nominal size. Limit dimensioning is a system of dimensioning where only the maximum and minimum dimensions arc shown. Thus, the tolerance is the difference between these two dimensions.Surface Finishing and Dimensional ControlProducts that have been completed to their proper shape and size frequently require some type of surface finishing to enable them to satisfactorily fulfill their function. In some cases, it is necessary to improve the physical properties of the surface material for resistance to penetration or abrasion. In many manufacturing processes, the product surface is left with dirt .chips, grease, or other harmful material upon it. Assemblies that are made of different materials, or from the same materials processed in different manners, may require some special surface treatment to provide uniformity of appearance.Surface finishing may sometimes become an intermediate step processing. For instance, cleaning and polishing are usually essential before any kind of plating process. Some of the cleaning procedures are also used for improving surface smoothness on mating parts and for removing burrs and sharp corners, which might be harmful in later use. Another important need for surface finishing is for corrosion protection in a variety of: environments. The type of protection procedure will depend largely upon the anticipated exposure, with due consideration to the material being protected and the economic factors involved.Satisfying the above objectives necessitates the use of main surface-finishing methods that involve chemical change of the surface mechanical work affecting surface properties, cleaning by a variety of methods, and the application of protective coatings, organic and metallic.In the early days of engineering, the mating of parts was achieved by machining one part as nearly as possible to the required size, machining the mating part nearly to size, and then completing its machining, continually offering the other part to it, until the desired relationship was obtained. If it was inconvenient to offer one part to the other part during machining, the final work was done at the bench by a fitter, who scraped the mating parts until the desired fit was obtained, the fitter therefore being a 'fitter' in the literal sense. J It is obvious that the two parts would have to remain together, and m the event of one having to be replaced, the fitting would have to be done all over again. In these days, we expect to be able to purchase a replacement fora broken part, and for it to function correctly without the need for scraping and other fitting operations.When one part can be used 'off the shelf' to replace another of the same dimension and material specification, the parts are said to be interchangeable. A system of interchangeability usually lowers the production costs as there is no need for an expensive, 'fiddling' operation, and it benefits the customer in the event of the need to replace worn parts.Automatic Fixture DesignTraditional synchronous grippers for assembly equipment move parts to the gripper centre-line, assuring that the parts will be in a known position after they arc picked from a conveyor or nest. However, in some applications, forcing the part to the centre-line may damage cither the part or equipment. When the part is delicate and a small collision can result in scrap, when its location is fixed by a machine spindle or mould, or when tolerances are tight, it is preferable to make a gripper comply with the position of the part, rather than the other way around. For these tasks, Zaytran Inc. Of Elyria, Ohio, has created the GPN series of non- synchronous, compliant grippers. Because the force and synchronizations systems of the grippers are independent, the synchronization system can be replaced by a precision slide system without affecting gripper force. Gripper sizes range from 51b gripping force and 0.2 in. stroke to 40Glb gripping force and 6in stroke. GrippersProduction is characterized by batch-size becoming smaller and smaller and greater variety of products. Assembly, being the last production step, is particularly vulnerable to changes in schedules, batch-sizes, and product design. This situation is forcing many companies to put more effort into extensive rationalization and automation of assembly that was previouslyextensive rationalization and automation of assembly that was previously the case. Although the development of flexible fixtures fell quickly behind the development of flexible handling systems such as industrial robots, there are, nonetheless promising attempts to increase the flexibility of fixtures. The fact that fixtures are the essential product - specific investment of a production system intensifies the economic necessity to make the fixture system more flexible.Fixtures can be divided according to their flexibility into special fixtures, group fixtures, modular fixtures and highly flexible fixtures. Flexible fixtures are characterized by their high adaptability to different work pieces, and by low change-over time and expenditure.There are several steps required to generate a fixture, in which a work piece is fixed for a production task. The first step is to define the necessary position of the work piece in the fixture, based on the unmachined or base pan, and the working features. Following this, a combination of stability planes must be selected. These stability planes constitute the fixture configuration in which the work piece is fixed in the defined position, all the forces or torques are compensated,。
机械加工外文翻译、中英文翻译、机械类外文文献翻译
机械加工外文翻译、中英文翻译、机械类外文文献翻译The engine lathe is an old but still useful metal removal machine with many desirable attributes。
While it is no longer commonlyXXX。
In today's n shops。
it has largely been XXX。
turret lathes。
and automatic XXX of single-point tooling for maximum metal removal。
and the use of form tools for finished products that are on par with the fastest processing XXX.When it XXX for the engine lathe。
it largely depends on the skill of the operator。
Design XXX part for n。
it is XXX.XXX cutting tools。
XXX ns。
as the machine can perform these ns in one setup。
They are also capable of producing parts with high n and accuracy。
XXX industries.Now more than ever。
n machining XXX of a specific method。
the XXX.When designing for low quantities。
such as 100 or 200 parts。
it is most cost-effective to use a XXX。
designers should aim to minimize the number of ns required.Another n for n XXX。
机械加工外文翻译
附录附录1英文原文Basic Machining Operations and Cutting TechnologyBasic Machining OperationsMachine tools have evolved from the early foot-powered lathes of the Egyptians and John Wilkinson's boring mill. They are designed to provide rigid support for both the work piece and the cutting tool and can precisely control their relative positions and the velocity of the tool with respect to the work piece. Basically, in metal cutting, a sharpened wedge-shaped tool removes a rather narrow strip of metal from the surface of a ductile work piece in the form of a severely deformed chip. The chip is a waste product that is considerably shorter than the work piece from which it came but with a corresponding increase in thickness of the uncut chip. The geometrical shape of work piece depends on the shape of the tool and its path during the machining operation.Most machining operations produce parts of differing geometry. If a rough cylindrical work piece revolves about a central axis and the tool penetrates beneath its surface and travels parallel to the center of rotation, a surface of revolution is produced, and the operation is called turning. If a hollow tube is machined on the inside in a similar manner, the operation is called boring. Producing an external conical surface uniformly varying diameter is called taper turning, if the tool point travels in a path of varying radius, a contoured surface like that of a bowling pin can be produced; or, if the piece is short enough and the support is sufficiently rigid, a contoured surface could be produced by feeding a shaped tool normal to the axis of rotation. Short tapered or cylindrical surfaces could also be contour formed.Flat or plane surfaces are frequently required. They can be generated by radial turning or facing, in which the tool point moves normal to the axis of rotation. In other cases, it is more convenient to hold the work piece steady and reciprocate the tool across it in a series of straight-line cuts with a crosswise feed increment before each cutting stroke. This operation is called planning and is carried out on a shaper. For larger pieces it is easier to keep the tool stationary and draw the work piece under it as in planning. The tool is fed at each reciprocation. Contoured surfaces can be produced by using shaped tools.Multiple-edged tools can also be used. Drilling uses a twin-edged fluted tool for holes with depths up to 5 to 10 times the drill diameter. Whether thedrill turns or the work piece rotates, relative motion between the cutting edge and the work piece is the important factor. In milling operations a rotary cutter with a number of cutting edges engages the work piece. Which moves slowly with respect to the cutter. Plane or contoured surfaces may be produced, depending on the geometry of the cutter and the type of feed. Horizontal or vertical axes of rotation may be used, and the feed of the work piece may be in any of the three coordinate directions.Basic Machine ToolsMachine tools are used to produce a part of a specified geometrical shape and precise I size by removing metal from a ductile material in the form of chips. The latter are a waste product and vary from long continuous ribbons of a ductile material such as steel, which are undesirable from a disposal point of view, to easily handled well-broken chips resulting from cast iron. Machine tools perform five basic metal-removal processes: I turning, planning, drilling, milling, and grinding. All other metal-removal processes are modifications of these five basic processes. For example, boring is internal turning; reaming, tapping, and counter boring modify drilled holes and are related to drilling; bobbing and gear cutting are fundamentally milling operations; hack sawing and broaching are a form of planning and honing; lapping, super finishing. Polishing and buffing are variants of grinding or abrasive removal operations. Therefore, there are only four types of basic machine tools, which use cutting tools of specific controllable geometry: 1. lathes, 2. planers, 3. drilling machines, and 4. milling machines. The grinding process forms chips, but the geometry of the abrasive grain is uncontrollable.The amount and rate of material removed by the various machining processes may be I large, as in heavy turning operations, or extremely small, as in lapping or super finishing operations where only the high spots of a surface are removed.A machine tool performs three major functions: 1. it rigidly supports the work piece or its holder and the cutting tool; 2. it provides relative motion between the work piece and the cutting tool; 3. it provides a range of feeds and speeds usually ranging from 4 to 32 choices in each case.Speed and Feeds in MachiningSpeeds, feeds, and depth of cut are the three major variables for economical machining. Other variables are the work and tool materials, coolant and geometry of the cutting tool. The rate of metal removal and power required for machining depend upon these variables.The depth of cut, feed, and cutting speed are machine settings that must be established in any metal-cutting operation. They all affect the forces, the power, and the rate of metal removal. They can be defined by comparing them to the needle and record of a phonograph. The cutting speed (V) is represented by the velocity of- the record surface relative to the needle in the tone arm at any instant. Feed is represented by the advance of the needle radially inward perrevolution, or is the difference in position between two adjacent grooves. The depth of cut is the penetration of the needle into the record or the depth of the grooves.Turning on Lathe CentersThe basic operations performed on an engine lathe are illustrated. Those operations performed on external surfaces with a single point cutting tool are called turning. Except for drilling, reaming, and lapping, the operations on internal surfaces are also performed by a single point cutting tool.All machining operations, including turning and boring, can be classified as roughing, finishing, or semi-finishing. The objective of a roughing operation is to remove the bulk of the material as rapidly and as efficiently as possible, while leaving a small amount of material on the work-piece for the finishing operation. Finishing operations are performed to obtain the final size, shape, and surface finish on the work piece. Sometimes a semi-finishing operation will precede the finishing operation to leave a small predetermined and uniform amount of stock on the work-piece to be removed by the finishing operation.Generally, longer work pieces are turned while supported on one or two lathe centers. Cone shaped holes, called center holes, which fit the lathe centers are drilled in the ends of the work piece-usually along the axis of the cylindrical part. The end of the work piece adjacent to the tail stock is always supported by a tail stock center, while the end near the head stock may be supported by a head stock center or held in a chuck. The head stock end of the work piece may be held in a four-jaw chuck, or in a type chuck. This method holds the work piece firmly and transfers the power to the work piece smoothly; the additional support to the work piece provided by the chuck lessens the tendency for chatter to occur when cutting. Precise results can be obtained with this method if care is taken to hold the work piece accurately in the chuck.Very precise results can be obtained by supporting the work piece between two centers. A lathe dog is clamped to the work piece; together they are driven by a driver plate mounted on the spindle nose. One end of the Work piece is mecained;then the work piece can be turned around in the lathe to machine the other end. The center holes in the work piece serve as precise locating surfaces as well as bearing surfaces to carry the weight of the work piece and to resist the cutting forces. After the work piece has been removed from the lathe for any reason, the center holes will accurately align the work piece back in the lathe or in another lathe, or in a cylindrical grinding machine. The work piece must never be held at the head stock end by both a chuck and a lathe center. While at first thought this seems like a quick method of aligning the work piece in the chuck, this must not be done because it is not possible to press evenly with the jaws against the work piece while it is also supported by the center. The alignment provided by the center will not be maintained and the pressure of the jaws may damage the center hole, the lathe center, andperhaps even the lathe spindle. Compensating or floating jaw chucks used almost exclusively on high production work provide an exception to the statements made above. These chucks are really work drivers and cannot be used for the same purpose as ordinary three or four-jaw chucks.While very large diameter work pieces are sometimes mounted on two centers, they are preferably held at the headstock end by faceplate jaws to obtain the smooth power transmission; moreover, large lathe dogs that are adequate to transmit the power not generally available, although they can be made as a special. Faceplate jaws are like chuck jaws except that they are mounted on a faceplate, which has less overhang from the spindle bearings than a large chuck would have.Introduction of MachiningMachining as a shape-producing method is the most universally used and the most important of all manufacturing processes. Machining is a shape-producing process in which a power-driven device causes material to be removed in chip form. Most machining is done with equipment that supports both the work piece and cutting tool although in some cases portable equipment is used with unsupported work piece.Low setup cost for small Quantities. Machining has two applications in manufacturing. For casting, forging, and press working, each specific shape to be produced, even one part, nearly always has a high tooling cost. The shapes that may he produced by welding depend to a large degree on the shapes of raw material that are available. By making use of generally high cost equipment but without special tooling, it is possible, by machining; to start with nearly any form of raw material, so tong as the exterior dimensions are great enough, and produce any desired shape from any material. Therefore .machining is usually the preferred method for producing one or a few parts, even when the design of the part would logically lead to casting, forging or press working if a high quantity were to be produced.Close accuracies, good finishes. The second application for machining is based on the high accuracies and surface finishes possible. Many of the parts machined in low quantities would be produced with lower but acceptable tolerances if produced in high quantities by some other process. On the other hand, many parts are given their general shapes by some high quantity deformation process and machined only on selected surfaces where high accuracies are needed. Internal threads, for example, are seldom produced by any means other than machining and small holes in press worked parts may be machined following the press working operations.Primary Cutting ParametersThe basic tool-work relationship in cutting is adequately described by means of four factors: tool geometry, cutting speed, feed, and depth of cut.The cutting tool must be made of an appropriate material; it must be strong, tough, hard, and wear resistant. The tool s geometry characterized by planes and angles, must be correct for each cutting operation. Cutting speed is the rate at which the work surface passes by the cutting edge. It may be expressed in feet per minute.For efficient machining the cutting speed must be of a magnitude appropriate to the particular work-tool combination. In general, the harder the work material, the slower the speed.Feed is the rate at which the cutting tool advances into the work piece. "Where the work piece or the tool rotates, feed is measured in inches per revolution. When the tool or the work reciprocates, feed is measured in inches per stroke, Generally, feed varies inversely with cutting speed for otherwise similar conditions.The depth of cut, measured inches is the distance the tool is set into the work. It is the width of the chip in turning or the thickness of the chip in a rectilinear cut. In roughing operations, the depth of cut can be larger than for finishing operations.The Effect of Changes in Cutting Parameters on Cutting TemperaturesIn metal cutting operations heat is generated in the primary and secondary deformation zones and these results in a complex temperature distribution throughout the tool, work piece and chip. A typical set of isotherms is shown in figure where it can be seen that, as could be expected, there is a very large temperature gradient throughout the width of the chip as the work piece material is sheared in primary deformation and there is a further large temperature in the chip adjacent to the face as the chip is sheared in secondary deformation. This leads to a maximum cutting temperature a short distance up the face from the cutting edge and a small distance into the chip.Since virtually all the work done in metal cutting is converted into heat, it could be expected that factors which increase the power consumed per unit volume of metal removed will increase the cutting temperature. Thus an increase in the rake angle, all other parameters remaining constant, will reduce the power per unit volume of metal removed and the cutting temperatures will reduce. When considering increase in unreformed chip thickness and cutting speed the situation is more complex. An increase in undeformed chip thickness tends to be a scale effect where the amounts of heat which pass to the work piece, the tool and chip remain in fixed proportions and the changes in cutting temperature tend to be small. Increase in cutting speed; however, reduce the amount of heat which passes into the work piece and this increase the temperature rise of the chip m primary deformation. Further, the secondary deformation zone tends to be smaller and this has the effect of increasing the temperatures in this zone. Other changes in cutting parameters have virtually no effect on the power consumed per unit volume of metal removed and consequently have virtually no effect on the cutting temperatures. Since ithas been shown that even small changes in cutting temperature have a significant effect on tool wear rate it is appropriate to indicate how cutting temperatures can be assessed from cutting data.The most direct and accurate method for measuring temperatures in high -speed-steel cutting tools is that of Wright &. Trent which also yields detailed information on temperature distributions in high-speed-steel cutting tools. The technique is based on the metallographic examination of sectioned high-speed-steel tools which relates microstructure changes to thermal history.Trent has described measurements of cutting temperatures and temperature distributions for high-speed-steel tools when machining a wide range of work piece materials. This technique has been further developed by using scanning electron microscopy to study fine-scale microstructure changes arising from over tempering of the tempered martens tic matrix of various high-speed-steels. This technique has also been used to study temperature distributions in both high-speed -steel single point turning tools and twist drills.Wears of Cutting ToolDiscounting brittle fracture and edge chipping, which have already been dealt with, tool wear is basically of three types. Flank wear, crater wear, and notch wear. Flank wear occurs on both the major and the minor cutting edges. On the major cutting edge, which is responsible for bulk metal removal, these results in increased cutting forces and higher temperatures which if left unchecked can lead to vibration of the tool and work piece and a condition where efficient cutting can no longer take place. On the minor cutting edge, which determines work piece size and surface finish, flank wear can result in an oversized product which has poor surface finish. Under most practical cutting conditions, the tool will fail due to major flank wear before the minor flank wear is sufficiently large to result in the manufacture of an unacceptable component.Because of the stress distribution on the tool face, the frictional stress in the region of sliding contact between the chip and the face is at a maximum at the start of the sliding contact region and is zero at the end. Thus abrasive wear takes place in this region with more wear taking place adjacent to the seizure region than adjacent to the point at which the chip loses contact with the face. This result in localized pitting of the tool face some distance up the face which is usually referred to as catering and which normally has a section in the form of a circular arc. In many respects and for practical cutting conditions, crater wear is a less severe form of wear than flank wear and consequently flank wear is a more common tool failure criterion. However, since various authors have shown that the temperature on the face increases more rapidly with increasing cutting speed than the temperature on the flank, and since the rate of wear of any type is significantly affected by changes in temperature, crater wear usually occurs at high cutting speeds.At the end of the major flank wear land where the tool is in contact with the uncut work piece surface it is common for the flank wear to be more pronounced than along the rest of the wear land. This is because of localised effects such as a hardened layer on the uncut surface caused by work hardening introduced by a previous cut, an oxide scale, and localised high temperatures resulting from the edge effect. This localised wear is usually referred to as notch wear and occasionally is very severe. Although the presence of the notch will not significantly affect the cutting properties of the tool, the notch is often relatively deep and if cutting were to continue there would be a good chance that the tool would fracture.If any form of progressive wear allowed to continue, dramatically and the tool would fail catastrophically, i. e. the tool would be no longer capable of cutting and, at best, the work piece would be scrapped whilst, at worst, damage could be caused to the machine tool. For carbide cutting tools and for all types of wear, the tool is said to have reached the end of its useful life long before the onset of catastrophic failure. For high-speed-steel cutting tools, however, where the wear tends to be non-uniform it has been found that the most meaningful and reproducible results can be obtained when the wear is allowed to continue to the onset of catastrophic failure even though, of course, in practice a cutting time far less than that to failure would be used. The onset of catastrophic failure is characterized by one of several phenomena, the most common being a sudden increase in cutting force, the presence of burnished rings on the work piece, and a significant increase in the noise level.Mechanism of Surface Finish ProductionThere are basically five mechanisms which contribute to the production of a surface which have been machined. These are:(l) The basic geometry of the cutting process. In, for example, single point turning the tool will advance a constant distance axially per revolution of the workpiecc and the resultant surface will have on it, when viewed perpendicularly to the direction of tool feed motion, a series of cusps which will have a basic form which replicates the shape of the tool in cut.(2) The efficiency of the cutting operation. It has already been mentioned that cutting with unstable built-up-edges will produce a surface which contains hard built-up-edge fragments which will result in a degradation of the surface finish. It can also be demonstrated that cutting under adverse conditions such as apply when using large feeds small rake angles and low cutting speeds, besides producing conditions which lead to unstable built-up-edge production, the cutting process itself can become unstable and instead of continuous shear occurring in the shear zone, tearing takes place, discontinuous chips of uneven thickness are produced, and the resultant surface is poor. This situation is particularly noticeable when machining very ductile materials such as copper and aluminum.(3) The stability of the machine tool. Under some combinations of cutting conditions; work piece size, method of clamping ,and cutting tool rigidity relative to the machine tool structure, instability can be set up in the tool which causes it to vibrate. Under some conditions this vibration will reach and maintain steady amplitude whilst under other conditions the vibration will built up and unless cutting is stopped considerable damage to both the cutting tool and work piece may occur. This phenomenon is known as chatter and in axial turning is characterized by long pitch helical bands on the work piece surface and short pitch undulations on the transient machined surface.(4)The effectiveness of removing swarf. In discontinuous chip production machining, such as milling or turning of brittle materials, it is expected that the chip (swarf) will leave the cutting zone either under gravity or with the assistance of a jet of cutting fluid and that they will not influence the cut surface in any way. However, when continuous chip production is evident, unless steps are taken to control the swarf it is likely that it will impinge on the cut surface and mark it. Inevitably, this marking besides looking.(5)The effective clearance angle on the cutting tool. For certain geometries of minor cutting edge relief and clearance angles it is possible to cut on the major cutting edge and burnish on the minor cutting edge. This can produce a good surface finish but, of course, it is strictly a combination of metal cutting and metal forming and is not to be recommended as a practical cutting method. However, due to cutting tool wear, these conditions occasionally arise and lead to a marked change in the surface characteristics.Limits and TolerancesMachine parts are manufactured so they are interchangeable. In other words, each part of a machine or mechanism is made to a certain size and shape so will fit into any other machine or mechanism of the same type. To make the part interchangeable, each individual part must be made to a size that will fit the mating part in the correct way. It is not only impossible, but also impractical to make many parts to an exact size. This is because machines are not perfect, and the tools become worn. A slight variation from the exact size is always allowed. The amount of this variation depends on the kind of part being manufactured. For examples part might be made 6 in. long with a variation allowed of 0.003 (three-thousandths) in. above and below this size. Therefore, the part could be 5.997 to 6.003 in. and still be the correct size. These are known as the limits. The difference between upper and lower limits is called the tolerance.A tolerance is the total permissible variation in the size of a part.The basic size is that size from which limits of size arc derived by the application of allowances and tolerances.Sometimes the limit is allowed in only one direction. This is known as unilateral tolerance.Unilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is shown in only one direction from the nominal size. Unilateral tolerancing allow the changing of tolerance on a hole or shaft without seriously affecting the fit.When the tolerance is in both directions from the basic size it is known as a bilateral tolerance (plus and minus).Bilateral tolerancing is a system of dimensioning where the tolerance (that is variation) is split and is shown on either side of the nominal size. Limit dimensioning is a system of dimensioning where only the maximum and minimum dimensions arc shown. Thus, the tolerance is the difference between these two dimensions.Surface Finishing and Dimensional ControlProducts that have been completed to their proper shape and size frequently require some type of surface finishing to enable them to satisfactorily fulfill their function. In some cases, it is necessary to improve the physical properties of the surface material for resistance to penetration or abrasion. In many manufacturing processes, the product surface is left with dirt .chips, grease, or other harmful material upon it. Assemblies that are made of different materials, or from the same materials processed in different manners, may require some special surface treatment to provide uniformity of appearance.Surface finishing may sometimes become an intermediate step processing. For instance, cleaning and polishing are usually essential before any kind of plating process. Some of the cleaning procedures are also used for improving surface smoothness on mating parts and for removing burrs and sharp corners, which might be harmful in later use. Another important need for surface finishing is for corrosion protection in a variety of: environments. The type of protection procedure will depend largely upon the anticipated exposure, with due consideration to the material being protected and the economic factors involved.Satisfying the above objectives necessitates the use of main surface-finishing methods that involve chemical change of the surface mechanical work affecting surface properties, cleaning by a variety of methods, and the application of protective coatings, organic and metallic.In the early days of engineering, the mating of parts was achieved by machining one part as nearly as possible to the required size, machining the mating part nearly to size, and then completing its machining, continually offering the other part to it, until the desired relationship was obtained. If it was inconvenient to offer one part to the other part during machining, the final work was done at the bench by a fitter, who scraped the mating parts until the desired fit was obtained, the fitter therefore being a 'fitter' in the literal sense. J It is obvious that the two parts would have to remain together, and m the event of one having to be replaced, the fitting would have to be done all over again. In these days, we expect to be able to purchase a replacement fora broken part, and for it to function correctly without the need for scraping and other fitting operations.When one part can be used 'off the shelf' to replace another of the same dimension and material specification, the parts are said to be interchangeable. A system of interchangeability usually lowers the production costs as there is no need for an expensive, 'fiddling' operation, and it benefits the customer in the event of the need to replace worn parts.Automatic Fixture DesignTraditional synchronous grippers for assembly equipment move parts to the gripper centre-line, assuring that the parts will be in a known position after they arc picked from a conveyor or nest. However, in some applications, forcing the part to the centre-line may damage cither the part or equipment. When the part is delicate and a small collision can result in scrap, when its location is fixed by a machine spindle or mould, or when tolerances are tight, it is preferable to make a gripper comply with the position of the part, rather than the other way around. For these tasks, Zaytran Inc. Of Elyria, Ohio, has created the GPN series of non- synchronous, compliant grippers. Because the force and synchronizations systems of the grippers are independent, the synchronization system can be replaced by a precision slide system without affecting gripper force. Gripper sizes range from 51b gripping force and 0.2 in. stroke to 40Glb gripping force and 6in stroke. GrippersProduction is characterized by batch-size becoming smaller and smaller and greater variety of products. Assembly, being the last production step, is particularly vulnerable to changes in schedules, batch-sizes, and product design. This situation is forcing many companies to put more effort into extensive rationalization and automation of assembly that was previouslyextensive rationalization and automation of assembly that was previously the case. Although the development of flexible fixtures fell quickly behind the development of flexible handling systems such as industrial robots, there are, nonetheless promising attempts to increase the flexibility of fixtures. The fact that fixtures are the essential product - specific investment of a production system intensifies the economic necessity to make the fixture system more flexible.Fixtures can be divided according to their flexibility into special fixtures, group fixtures, modular fixtures and highly flexible fixtures. Flexible fixtures are characterized by their high adaptability to different work pieces, and by low change-over time and expenditure.There are several steps required to generate a fixture, in which a work piece is fixed for a production task. The first step is to define the necessary position of the work piece in the fixture, based on the unmachined or base pan, and the working features. Following this, a combination of stability planes must be selected. These stability planes constitute the fixture configuration in which the work piece is fixed in the defined position, all the forces or torques are compensated,。
机械加工切削加工中英文对照外文翻译文献
机械加工切削加工中英文对照外文翻译文献中英文资料翻译英文部分The new concept of cutting processingThe nowadays cutting tool company cannot only be again the manufacture and the sales cutting tool, in order to succeed, they must be consistent with the globalization manufacture tendency maintenance, through enhances the efficiency, cooperates with the customer reduces the cost. Approaches the instantaneous global competition after this after NAFTA, the WTO time, the world company is making quickly to the same feeling, is lighter, a cheaper response. In other words, they make the product and the components contain can in high speed under revolve, as a result of the cost pressure, best, is lighter moreover must make cheaply. Obtains these goals a best way is through develops and applies the new material, but these is new and the improvement material usually all with difficulty processes. In in this kind of commercial power and the technical difficulty combination is especially prominent in the automobile and the aviation industry, and has become has the experience the cutting tool company to research and develop the department the most important driving influence.For example, takes the modular cast iron to say that, it has become the engine part and other automobiles, the agriculture the material which see day by day with the equipment and in the machine tool industry components. This kind of alloy provides the low production cost and the good machine capability combination. They are cheaper than the steel products, but has a higher intensity and toughness compared to the cast iron. But atthe same time the modular cast iron is extremely wear-resisting, has fast breaks by rubbing the cutting tool material the tendency. In this wear resistant very great degree bead luminous body content influence. Some known modular cast iron bead luminous body content higher, its resistance to wear better, moreover its machinability is worse. Moreover, the modular cast iron porosity causes off and on to cut, this even more reduces the life.May estimate that, the high degree of hardness and the high wear-resisting cutting material quality must consider the modular cast iron the high resistance to wear. And the material quality contains extremely hard TiC in fact (carbonized titanium) or TiCN (carbon titanium nitrides) thick coating when cutting speed each minute 300 meters processes the modular cast iron to prove usually is effective. But along with cutting speed increase, scrap/The cutting tool junctionplane temperature also is increasing. When has such situation, the TiC coating favors in has the chemical reaction with the iron and softens, more pressures function in anti- crescent moon hollow attrition coating. Under these conditions, hoped has one chemical stability better coating, like Al2O3 (although under low speed was inferior to TiC hard or is wear-resisting).The chemical stability becomes an important performance performance dividing line compared to the resistance to wear the factor, the speed and the temperature is decided in is processed the modular cast iron the crystal grain structure and the performance. But usually thick coating of TiCN and TiC or only ductile iron oxides in the soil coating is applied to, because the today majority of this kinds are processed the material the cutting speed in each minute 150 to 335 meters between. Is higher than each minute 300 meter applications regarding thespeed, the people to this kind of material are satisfied.In order to cause this scope performance to be most superior, the mountain high researched and developed and has promoted in view of modular cast iron processing material quality TX150. This kind of material quality has hard also the anti- distortion substrate, is very ideal regarding the processing modular cast iron. Its coating the oxide compound coating which hollowly wears by thick very wear-resisting carbon titanium nitrides and a thin anti- crescent moon, the top is thin layer TiN. This kind of coating which needs the center warm chemistry gas phase deposition using the state of the art production resistance to wear and the anti- crescent moon hollow attrition which the CVD coating complete degree of hardness moreover the tough smoothness increases (MTCVD) the craft. Substrate/The coating combination performance gives the very high anti- plastic deformation and the cutting edge micro collapses the ability, causes it to become under the normal speed to process the modular cast iron the ideal material quality.The coating ceramics also display can effectively process the modular cast iron. In the past, the aluminum oxide ceramics application which not the coating tough good such as nitriding silicon and the silicon carbide textile fiber strengthened the work piece material chemistry paralysis limit. Today but could resist the scrap distortion process through the use to have the high thermal coating cutting tool life already remarkably to increase. But certain early this domains work piece processing use aluminum oxides spread the layer crystals to have to strengthen the ceramics, today most research concentrate in the TiN coating nitriding silicon. This kind of coating can remarkably open up the tough good ceramics the application scope.When machining, the work piece has processed the surface is depends upon the cutting tool and the work piece makes the relative motion to obtain.According to the surface method of formation, the machining may divide into the knife point path law, the formed cutting tool law, the generating process three kinds.The knife point path law is depends upon the knife point to be opposite in the work piecesurface path, obtains the superficial geometry shape which the work piece requests, like the turning outer annulus, the shaping plane, the grinding outer annulus, with the profile turning forming surface and so on, the knife point path are decided the cutting tool and the work piece relative motion which provides in the engine bed;The formed cutting tool law abbreviation forming, is with the formed cutting tool which matches with the work piece final superficial outline, or the formed grinding wheel and so on processes the formed surface, like formed turning, formed milling and form grinding and so on, because forms the cutting tool the manufacture quite to be difficult, therefore only uses in processing the short formed surface generally;The generating process name rolls cuts method, is when the processing the cutting tool and the work piece do unfold the movement relatively, the cutting tool and the work piece centrode make the pure trundle mutually, between both maintains the definite transmission ratio relations, obtains the processing surface is the knife edge in this kind of movement envelope, in the gear processing rolls the tooth, the gear shaping, the shaving, the top horizontal jade piece tooth and rubs the tooth and so on to be the generating process processing.Somemachining has at the same time the knife point path law and the formed cutting tool method characteristic, like thread turning.The machining quality mainly is refers to the work piece the processing precision and the surface quality (including surface roughness, residual stress and superficial hardening).Along with the technical progress, the machining quality enhances unceasingly.The 18th century later periods, the machining precision counts by the millimeter; At the beginning of 20th century, machining precision Gao Yida 0.01 millimeter; To the 50's, the machining precision has reached a micron level; The 70's, the machining precision enhances to 0.1 micron.The influence machining quality primary factor has aspects and so on engine bed, cutting tool, jig, work piece semifinished materials, technique and processing environment.Must improve the machining quality, must take the suitable measure to the above various aspects, like reduces the engine bed work error, selects the cutting tool correctly, improves the semifinished materials quality, the reasonable arrangement craft, the improvement environmental condition and so on.Enhances the cutting specifications to enhance the material excision rate, is enhances the machining efficiency the essential way.The commonly used highly effective machining method has the high-speed cutting, the force cutting, the plasma arc heating cuts and vibrates the cutting and so on.The grinding speed is called the high-speed grinding in 45 meters/second above /doc/9c977104.html es the high-speed cutting (or grinding) both may enhance the efficiency, and mayreduce the surface roughness.The high-speed cutting (or grinding) requests the engine bed to have the high speed, thehigh rigidity, the high efficiency and the vibration-proof good craft system; Requests the cutting tool to have the reasonable geometry parameter and the convenience tight way, but also must consider the safe reliable chip breaking method.The force cutting refers to the roughing feed or cuts the deep machining greatly, uses in the turning and the grinding generally.The force turning main characteristic is the lathe tool besides the main cutting edge, but also some is parallel in the work piece has processed superficial the vice-cutting edge simultaneously to participate in the cutting, therefore may enhance to feed quantity compared to the general turning several times of even several /doc/9c977104.htmlpares with the high-speed cutting, the force cutting cutting temperature is low, the cutting tool life is long, the cutting efficiency is high; The shortcoming is processes the surface to be rough.When force cutting, the radial direction cutting force death of a parent is not suitable for to process the tall and slender work piece very much.The vibration cutting is along the cutting tool direction of feed, the attachment low frequency or the high frequency vibration machining, may enhance the cutting efficiency.The low frequency vibration cutting has the very good chip breaking effect, but does not use the chip breaking equipment, makes the knife edge intensity to increase, time the cutting total power dissipation compared to has the chip breaking installment ordinary cutting to reduce about 40%.The high frequency vibration cutting also called the ultrasonic wave vibration cutting, is helpful in reduces between the cutting tool and the work piece friction, reduces the cutting temperature, reduces the cuttingtool the coherence attrition, thus the enhancement cutting efficiency and the processing surface quality, the cutting tool life may enhance 40% approximately.To lumber, plastic, rubber, glass, marble, granite and so on nonmetallic material machining, although is similar with the metal material cutting, but uses the cutting tool, the equipment and the cutting specifications and so on has the characteristic respectively.The lumber product machining mainly carries in each kind of joiner's bench, its method mainly has: The saw cuts, digs cuts, the turning, the milling, drills truncates with the polishing and so on.The plastic rigidity is worse than the metal, the easy bending strain, the thermoplastic thermal conductivity to be in particular bad, easy to elevate temperature the conditioning.When cutting plastic, suitably with the high-speed steel or the hard alloy tools, selects the small to feed quantity and the high cutting speed, and uses compressed air cooling.If the cutting tool is sharp, the angle is appropriate, may produce the belt-shaped scrap, easy to carry off the quantity of heat.Glass (including semiconducting material and so on germanium, silicon) but degree of hardness high brittleness is big.To methods and so on glass machining commonly used cutting, drill hole, attrition and polishing.T o thickness in three millimeters following glass plates, the simple cutting method is with the diamond or other hard materials, in glass surface manual scoring, the use scratch place stress concentration, then uses the hand to break off.To the marble, the granite and the concrete and so on the hard material processing, mainly uses methods and so on cutting, turning, drill hole, shaping, attrition and polishing.When cuttingthe available circular saw blade adds the grinding compound and the water; The outer annulus and the end surface may use the negative rake the hard alloy lathe tool, by 10~30 meter/minute cutting speed turning; Drills a hole the available hard alloy drill bit; The big stone material plane available hard alloy planing tool or rolls cuts planing tool shaping; The precise smooth surface, available three mutually for the datum to the method which grinds, or the grinding and the polishing method obtains.Cutting tool in hot strong alloy applicationThe aviation processing also changes rapidly. For example, nickel base heat-resisting alloy like several years ago the most people had not heard Rene88 now occupies to the aircraft engine manufacture uses the total metal quantity 10~25%. Has very good showing and the commercial reason regarding this. For example, these heat strong alloy will be able to increase the engine endurance moreover to permit the small engine work on the big airplane, that will enhance the combustion efficiency and reduces the operation cost. These tough good materials also present the expense on the cutting tool. Their thermal stability causes on the knife point the temperature to be higher, thus reduced the cutting tool life. Similarly, in these alloy carbide pellet remarkably increased the friction, thus reduces the cutting tool life.As a result of changes in these conditions, can be very pleased to have processed many titanium alloys and nickel-based alloy materials C-2 hard metal alloys, in the application to today's cutting edge of blade to the crushing and cutting depth of the trench lines badly worn. But using the latest high-temperature processing of small particles hard metal alloys to be effective, cutlery life improved, but more importantly to enhance thereliability of applications in high-temperature alloys. Small particles hard metal than traditional hard metal materials higher compression strength and hardness, only a small increase in the resilience of the cost. And resulted in high temperature alloy processing than traditional hard metal resistance common failure mode more effective.PVD (physical gas phase deposition) coating also by certificate effective processing heat-resisting alloy. TiN (titanium nitrides) the PVD coating was uses and still was most early most receives welcome. Recently, TiAlN (nitrogen calorization titanium) and TiCN (carbontitanium nitrides) the coating also could very good use. In the past the TiAlN coating application scope and TiN compared the limit to be more. But after the cutting speed enhances them is a very good choice, enhances the productivity in these applications to reach 40%. On the other hand, is decided under the low cutting speed in coating superficial operating mode TiAlN can cause to accumulate the filings lump afterwards, micro collapses with the trench attrition.Recently, used in the heat-resisting alloy application material quality already developing, these coating but became by several combinations. The massive laboratories and the scene test has already proven this kind of combination and other any kind of sole coating compares in time the very wide scope application is very effective. Therefore aims at the heat-resisting alloy application the PVD compound coating possibly to become the focal point which the hard alloy new material quality research and development continues. With the MTCVD coating, the coating ceramics gather in the same place, they hopefully become a more effective processing to research and develop newly are moredifficult to process the work piece material the main impact strength.Dry processingIncluding the refrigerant question is technical and the commercial expansion industrial production tendency another domain which the cutting tool makes. North America and the European strict refrigerant management request and the biggest three automobile manufacturer forces them the core supplier to obtain the ISO14000 authentication (the ISO9000 environment management edition), this causes the refrigerant processing cost rise. To the car company and their core supplier said obviously one of responses which welcome is in the specific processing application avoids completely the refrigerant the use. This kind did the processing the new world to propose a series of challenges for the cutting tool supplier.Recently, already appeared some to concern this topic to promulgate the speed, to enter for, the coating chemical composition and other parameters very substantial comprehensive nature very strong useful technical papers. Wants to concentrate the elaboration in here me "does the processing viewpoint" in the operation and commercial meaning automobile manufacturer new.The metal working jobholders can the very good understanding related refrigerant use question, but majority cannot understand concerns except the technical challenge (for example row of filings) beside does the processing question in the cutting tool - work piece contact face between. Usually may observe to the refrigerant disperser scrap which flows out, but the pressure surpasses 3,000 pounds/An inch 2 high speed refrigerant also can help to break the filings, specially soft alsothe continual scrap can cause in the cutting tool - work piece contact face trouble.Uses does the cutting craft the components result is the engine bed uses the wet typeprocessing components to be hotter than. Whether before you do allow them to survey in the open-air natural cooling? If processes newly the hot components put frequently to the turnover box, elevates the environment temperature, whether components full cooling and just right enough permission precision examination? Also has the handling side several dozens on hundred components to be able to operate the worker to increase the extra burden.With many cutting tools/The work piece technical question same place, these latent questions need to state whether dryly adds the ability line. Luckily, has very many ways to elaborate these questions. For example, the compressed air was proven row of filings becomes the question in very many applications the situation to have the successful echo.Another plan is called MQL (minimum lubrication) a technology, it replaces the traditional refrigerant by the application the quite few oil mists constitution. This is a recognition compromise plan, this kind of minimum technology can large scale reduce the refrigerant the headache matter, moreover the smooth finish which processes in many applications very is also good. This domain still had very many research to do, moreover the cutting tool company positively participated in such research was absolutely essential. If they will not do fall behind the competitor, will be at the disadvantageous position.In the factory the special details design other perhaps betterplan according to the world in. The manufacturing industry jobholders possibly still could ask why they do have to use recent development the technology to replace the refrigerant method diligently which the tradition already an experience number generation of person improved enhances, because implemented especially does the experiment and the defeat which the processing or the subarid processing produced possibly causes the higher short-term cutting tool cost. The concise answer is when the bit probably accounts for the model processing components cost 3%, the refrigerant cost (from purchases to maintenance, storage, processing) can account for the components cost 15%.Perhaps does the dry processing is not all suits to each application, but above discusses likely other processing questions are same, needs from a wider operation, the environment and the commercial angle appraises. Will be able to help the cutting tool company which the customer will do this to have the competitive advantage, but these will not be able to provide unceasingly is in the passive position.Cutting tool and nanotechnologyCan fiercely change the cutting tool industry the enchanting new domain is the miniature manufacture, or the processing small granule forms the product which needs. Must refer to is its here does not have about the cutting tool miniature manufacture first matter; Second must say the matter is it is not remote.Why the miniature manufacture and are the cutting tool related. Because most main is theparticle size smaller, the hard alloy toughness of material better also is more wear-resisting. (Some experts define with the nanometer level pellet for are smaller than 0.2 mu m, but otherpeople persisted a nanometer pellet had to be smaller than the hard alloy tools prototype which 0.1 mu m) made already to complete and the test,It is said that wear resistant theatrically increase. The question is the nanometer level hard alloy pellet cannot depend on the smashing big material formation, they are certain through the smaller material constitution, but processes the molecular level granule is not easy and the economical matter.中文部分切削加工新概念现今的刀具公司再也不能只是制造和销售刀具，为了成功，他们必须与全球化制造趋势保持一致，通过提高效率、同客户合作来降低成本。
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毕业设计中英文翻译英文原文Hard gear processing[abstract ]uses in the power drive gear and the gear box, its size request smaller, the gear drive noise is lower, thus causes to the hard gear demand, also gave the gear manufacturer to propose explored the gear to process the new method the request OutlineUses in the power drive gear and the gear box, its size request smaller, the gear drive noise is lower, thus causes to the hard gear demand, also gave the gear manufacturer to propose explored the gear to process the new method the request. The gear in the hard heat treatment process, its material organization and the stress change, usually can cause the gear to have the distortion, namely tooth profile, tooth to and tooth pitch error. This this error will cause the tooth profile not correctly to mesh in the transmission time, thus has enlarged the load, will have the gear noise. Therefore, the hard gear after the heat treatment, should increase together the precision work working procedure generally.The hard gear precision work craft may divide into two kinds: A kind is uses non- formed the cutting edge, like the gear rubs truncates the processing; Another kind then is has formed the cutting edge like hard gear (HRC48 ~ 53) to roll truncates the processing.This article strongly will discuss will use in hardly rolling the hard alloy tools forming cutting edge precision work process which the tooth will process. The now hard alloy material, the cutting tool coating and the gear-hobbing machine technology development, has caused the hard gear to roll cuts the processing technology to have the remarkable enhancement, specially is smaller than in the processing or was equal to when 12DP center small modulus gear, may withstand the enormous cutting force which in the hard cutting process produces.Hard alloy hob selectionThe hard alloy hob has the very big progress in the material variety specification. Superfine, is thin, medium or the big pellet hard alloy now all has the product. In addition, the hard alloy hob semifinished materials formed craft technology also had the remarkable enhancement, like uses static pressure and so on heat (HIP) the craft, this craft under the high-pressured high temperature, increased the hard alloy semifinished materials intrinsic binding force, enhanced the hard alloy anti- curved intensity. According to the ISO stipulation, the entity hard alloy material may differently divide into certain kinds according to the application situation: The gear cutting tool divides into K kind and P kind, K kind of hard alloy has a higherresistance to wear, P kind then has the better high temperature red hardness. In the K trademark and in the P trademark hard alloy, each kind of trademark hard alloy granular structure is different, from medium pellet to superfine pellet. Each kind of trademark all has its application situation, this is and the granular structure is connected. Generally speaking, regarding softly rolls truncates, the K analogy P kind of performance is friends with, K kind of hard alloy can obtain a micron level the granular structure (granularity to be smaller than 0.5 mu m), but P kind then is not good. In abrasion aspect, K kind of toughness better, the life is longer.The hob resharpens and renovatesAfter the hob processing certain quantity work piece, its cutting edge failure, this time must resharpen. Sharpens the after hob to have to maintain the original geometry shape; The cutting edge must be sharp; The cutting tool golden phase structure cannot because rub truncates the heat but to destroy. Thus when sharpens the hard alloy hob should use one kind of oil base refrigerant, it does not get up to the chlorine and the sulfur the response. Regarding scrapes the hob, sharpens after the coating not likely to use in hob such which the entity semifinished materials hardly rolls being important again. After the hard alloy hob sharpens in front of the coating, suggested carries on the pretreatment to its cutting edge.The hob rewill sharpen can except the cutting surface original coating, this will be able to reduce the cutting tool life. The cutting tool is may again spread. Usually regarding the TiN coating, may spread 3 ~ 4; Says regarding TiCN and the TiALN coating, because coating itself has the very big internal stress, therefore on cutting edge with difficulty again again coating. After several spreading TiN coating, can have the height non-uniformity condition, and influentials the tendency which the level falls off, therefore the original coating must remove.At present has two methods to be possible to remove the cutting tool coating: Chemistry draws back spreads draws back with physics spreads. Draws back with chemistry spreads removes on the hard alloy tools the coating is one kind of fine craft, requests the operator to have the suitable level of expertise. The excessively chemistry draws back spreads not only removes the coating, moreover also will dissolve washes the cobalt cement, the damage hard alloy material microscopic structure. The cutting edge microscopic damage will produce the zigzag surface. In addition, when draws back spreads must to the hob pillow block, in the hole and the sign carries on the protection, in order to avoid damages. But physics spreads, then must carry on by the original cutting tool factory, it involves to puts in order rerubs the hob tooth profile truncates. Although draws back chemistry spreads must be much more expensive than, but obtains is a new hob, the quality and the life all can obtain the guarantee.To gear-hobbing machine requestIn order to fully displays the hard alloy and the coating craft merit, the gear-hobbing machine should do correspondingly improves. At present all advanced gear-hobbing machines all press high speed roll the tooth to carry on the design, its gear-hobbing machine hob rotational speed surpasses 3000r/Min, usually is5000r/Min, the work piece main axle rotational speed and the hob rotational speed match. In addition, the engine bed has very high moves the rigidity and the hot rigidity. The advanced gear-hobbing machine some main design characteristics are: Uses the compound epoxy resin lathe bed, by improves the engine bed the tendency and the static characteristic; Has the constant temperature installment the high speed hob headstock; High speed work piece main axle; May use does, the wet two kinds rolls truncates the craft; Belt electro-optical sensor digital actuation system; The straight line rolls the guide rail system; High speed automatic high-quality goods (2 ~ 3 seconds); The occupying a land area of is compact; According to man-machine engineering design; Services conveniently.Uses scrapes the craftRegardless of is the mechanical type the CNC gear-hobbing machine all can carry on scrapes, but the condition is the engine bed must equip has the work piece to the cutting tool selsyn train system. This may cause to scrape the craft economically, to has on the automatic yummy treats system the engine bed very to be also important. The electronic non- contact system depends on a simulation quantity sensor to send out the pulse to survey the cutting tool main axle, the work piece main axle and the gear position. The engine bed CNC controller carries on processing to these pulses, then is opposite to the work piece main axle in the cutting tool position carries on the adjustment, causes a work piece turn of tooth and the hob knife tooth relative position relations is correct.In scrapes in the craft to have very many merits with the refrigerant: In scrapes in the process, the refrigerant has provided the lubricating ability; Because scrapes produces is not the normal scrap, the temperature control is extremely important. Blows the scrap small is thin, does not look like normal knife filings such to be possible to carry off many quantity of heats, therefore scrapes time uses the refrigerant to be possible to control the cutting tool, the work piece and the engine bed system temperature; The refrigerant may washes away the scrap from the cutting tool and the work piece; Improved the work piece surface fine roughness; Enhanced the cutting tool life."Rolls in the green truncates" in the craft, correctly chooses the tooth thick remainder is very important. The recommendation choice down milling rolls the tooth, because it may obtain the thickest scrap, this is helpful to the control cutting process dynamic condition, enhances the cutting tool life. The experience proved that, the cutting speed may surpass 200m/Min, enters for the quantity choice is decided by the superficially attractive fineness which must achieve. The model enters for the scope is 0.5 ~ 1.25mm/R. The cutting tool shifts (flees knife) the method very to be also important, because scrapes time only then the rough machining section partial cutting edges only then undergo the attrition. On the contrary, in "the green cutting" in the process, the cutting tool precision work has partially undertaken the main process load. This meant when scraping flees the knife quantity to be supposed to be bigger, when like the gear is 12 ~ 48DP, each time flees the knife quantity is 0.3 ~ 0.4mm.Scrapes the hob the selectionScrapes the hard alloy hob to divide into two big kinds: Uses in 10DP or the bigger modulus hob, usually all designs has a negative rake front the cutting, when the cutting edge contacts to the hard tooth face, reduced to the hard alloy material impact; Regarding the small modulus gear, does not need to have the negative rake. The negative rake hob shortcoming is sharpens the difficulty. After the hob sharpens the outer diameter to reduce, in order to obtain the correct negative rake to be supposed to change the grinding wheel the bias quantity.When scrapes, the big modulus gear, its addendum, the outer annulus diameter and the tooth root spot all are usually not rolled truncates, and has a smooth transition a request turn of tooth to the tooth root. In order to obtain sinks cuts with the integrity transition circular arc radius, enhances the tooth root the anti- curved intensity, uses in the big modulus gear ideal scraping the hob to be supposed to have the flange. Regarding the small modulus gear processing, should use the standard hob. Uses the standard in front of the radial direction the angle hard alloy hob processing to be called "the hard alloy hob to roll again cuts", but is not "scrapes", latter referred has used a negative rake hob.Hardly rolls the specification which truncates and hardly scrapes the specification which, or the hard alloy hob rolls again truncates nearly same, similarity is uses the strategy which flees the knife to shift to be different. When hardly rolls, the scrap excision must spend the massive energies. This energy finally becomes the quantity of heat. Tries to carry off very important these thermal sending out. After the suggestion processes a work piece every time, the hob flees a position entire tooth pitch. When the hob will flee from beginning to end the position from now on, will be supposed to transfer to the hob to the initial position has a bias quantity the spot. This bias quantity is decided by the hob design and the application, its goal is for be helpful to the hob uniform wear. Another one similarity is the attire which uses clamps the system. As a result of the enormous cutting force, the jig must safely clamp the work piece. The processing result indicated that, the identical helical gear when hardly rolls again with the hard alloy hob, its gear quality is very high, the tooth profile approaches the AGMA10 level, the tooth to surpasses the AGMA12 level with the tooth pitch; The entire hard semifinished materials hardly roll cut the processing the helical gear, its gear precision extremely is also high, the tooth profile precision may reach the AGMA10 level, the tooth to may achieve the AGMA12 level with the tooth pitch. ConclusionAt present has explored many economies the method to process the hard gear, including the material choice, the soft processing method, the heat treatment craft and the hard precision work, enable the hard gear to obtain the popularization, has satisfied the high grade transmission device to the hard gear request.Carries on from entity entire hard work piece semifinished materials hardly rolls cuts the processing is one kind of new processing craft. Because has a rigid better engine bed and the high quality hard alloy tools material and performs coating processing, causes hardly to roll slivers is one effective processing method. Indicatedfrom the factory practical application result that, the hard gear rolls cuts (hardly rolls) the craft to have the broad application prospect.译文：淬硬齿轮的加工【摘要】用于动力传动的齿轮和齿轮箱，其尺寸要求更小，齿轮传动的噪音更低，从而导致对淬硬齿轮的需求，也给齿轮制造厂家提出了探索齿轮加工新方法的要求.概述用于动力传动的齿轮和齿轮箱，其尺寸要求更小，齿轮传动的噪音更低，从而导致对淬硬齿轮的需求，也给齿轮制造厂家提出了探索齿轮加工新方法的要求。