机械专业毕业设计外文翻译10

翻译部分

英文部分

ADV ANCED MACHINING PROCESSES

As the hardware of an advanced technology becomes more complex, new and visionary approaches to the processing of materials into useful products come into common use. This has been the trend in machining processes in recent years.. Advanced methods of machine control as well as completely different methods of shaping materials have permitted the mechanical designer to proceed in directions that would have been totally impossible only a few years ago.

Parallel development in other technologies such as electronics and computers have made available to the machine tool designer methods and processes that can permit a machine tool to far exceed the capabilities of the most experienced machinist.

In this section we will look at CNC machining using chip-making cutting tools. CNC controllers are used to drive and control a great variety of machines and mechanisms, Some examples would be routers in wood working; lasers, plasma-arc, flame cutting, and waterjets for cutting of steel plate; and controlling of robots in manufacturing and assembly. This section is only an overview and cannot take the place of a programming manual for a specific machine tool. Because of the tremendous growth in numbers and capability of comp uters ,changes in machine controls are rapidly and constantly taking place. The exciting part of this evolution in machine controls is that programming becomeseasier with each new advanced in this technology.

Advantages of Numerical Control

A manually operated machine tool may have the same physical characteristics as a CNC machine, such as size and horsepower. The principles of metal removal are the same. The big gain comes from the computer controlling the machining axes movements. CNC-controlled machine tools can be as simple as a 2-axis drilling machining center (Figure O-1). With a dual spindle machining center, the low RPM, high horsepower spindle gives high metal removal rates. The high RPM spindle allows the efficient use of high cutting speed tools such as diamonds and small diameter cutters (Figure O-2). The cutting tools that remove materials are standard tools such as milling cutters, drills, boring tools, or lathe tools depending on the type of machine used. Cutting speeds and feeds need to be correct as in any other machining operation. The greatest advantage in CNC machining comes from the unerring and rapid positioning movements possible. A CNC machine does dot stop at the end of a cut to plan its next move; it does not get fatigued; it is capable of uninterrupted machining error free, hour after hour. A machine tool is productive only while it is making chips.

Since the chip-making process is controlled by the proper feeds and speeds, time savings can be achieved by faster rapid feed rates. Rapid feeds have increased from 60 to 200 to 400 and are now often approaching 1000 inches per minute (IPM). These high feed rates can pose a safety hazard to anyone within the working envelope of the machine tool.

Complex contoured shapes were extremely difficult to product prior to CNC machining .CNC has made the machining of these shapes economically feasible. Design changes on a part are relatively easy to make by changing the program that directs the machine tool.

A CNC machine produces parts with high dimensional accuracy and close tolerances without taking extra time or special precautions, CNC machines generally need less complex work-holding fixtures, which saves time by getting the parts machined sooner. Once a program is ready and production parts, each part will take exactly the same amount of time as the previous one. This repeatability allows for a very precise control of production costs. Another advantage of CNC machining is the elimination of large inventories; parts can be machined as needs .In conventional production often a great number of parts must be made at the same time to be cost effective. With CNC even one piece can be machined economically .In many instances, a CNC machine can perform in one setup the same operations that would require several conventional machines.

With modern CNC machine tools a trained machinist can program and product even a single part economically .CNC machine tools are used in small and large machining facilities and range in size from tabletop models to huge machining centers. In a facility with many CNC tools, programming is usually done by CNC programmers away from the CNC tools. The machine control unit (MCU) on the machine is then used mostly for small program changes or corrections. Manufacturing with CNC tools usually requires three categories of persons. The first is the programmer, who is responsible for developing machine-ready code. The next person involved is the setup person, who loads the raw stork into the MCU, checks that the co rrect tools are loaded, and makes the first part. The third person is the machine and unloads the finished parts. In a small company, one person is expected to perform all three of these tasks.

CNC controls are generally divided into two basic categories. One uses a ward address format with coded inputs such as G and M codes. The other users a conversational input; conversational input is also called user-friendly or prompted input. Later in this section examples of each of these programming formats in machining applications will be describes.

CAM and CNC

CAM systems have changed the job of the CNC programmer from one manually producing CNC code to one maximizing the output of CNC machines. Since CNC machine tools are made by a great number of manufacturers, many different CNC control units are in use. Control units from different manufacturers use a variety of program formats and codes. Many CNC code words are identical for different controllers, but a great number vary from one to another.

To produce an identical part on CNC machine tools with different controllers such as one by FANCU, OKUMA or DYNAPATH, would require completely different CNC codes. Each manufacturer is constantly improving and updating its CNC controllers. These improvements often include additional code words plus changes in how the existing code works.

A CAM systems allows the CNC programmer to concentrate on the creation of an efficient machining process, rather then relearning changed code formats. A CNC programmer looks at

the print of a part and then plans the sequence of machining operations necessary to make it (Figure O-3). This plan includes everything, from the selection of possible CNC machine tools, to which tooling to use, to how the part is held while machining takes place. The CNC programmer has to have a thorough understanding of all the capacities and limitations of the CNC machine tools that a program is to be made for. Machine specifications such as horsepower, maximum spindle speeds, workpiece weight and size limitations, and tool changer capacity are just some of the considerations that affect programming.

Another area of major importance to the programmer is the knowledge of machining processes. An example would be the selection of the surface finish requirement specified in the part print. The sequence of machining processes is critical to obtain acceptable results. Cutting tool limitations have to be considered and this requires knowledge of cutting tool materials, tool types, and application recommendations.

A good programmer will spend a considerable amount of time in researching the rapidly growing volume of new and improved tools and tool materials. Often the tool that was on the cutting edge of technology just two years ago is now obsolete. Information on new tools can come from catalogs or tool manufacturers' tooling engineers. Help in tool selection or optimum tool working conditions can also be obtained from tool manufacturer software. Examples would be Kennametal's "TOOLPRO", software designed to help select the best tool grade, speed, and feed rates for different work materials in turning application. Another very important feature of "TOOLPRO" is the display of the horsepower requirement for each machining selection. This allow the programmer to select a combination of cutting speed, feed rate, and depth of cut that equals the machine's maximum horsepower for roughing cuts. For a finishing cut, the smallest diameter of the part being machined is selected and then the cutting speed varied until the RPM is equal to the maximum RPM of the machine. This helps in maximizing machining efficiency. Knowing the horsepower requirement for a cut is critical if more than one tool is cutting at the same time.

Software for a machining center application would be Ingersoll Tool Company's "Actual Chip Thickness", a program used to calculate the chip thickness in relation to feed-per-tooth for a milling cutter, especially during a shallow finishing cut. Ingersoll's "Rigidity Analysis" software ealculates tool deflection for end mills as a function of tool stiffness and tool force.

To this point we looked at some general qualifications that a programmer should possess. Now we examine how a CAM system works. Point Control Company's SmartCam system uses the following approach. First, the programmer makes a mental model of the part to be machined. This includes the kind of machining to be performed-turning or milling. Then the part print is studied to develop a machining sequence, roughing and finishing cuts, drilling, tapping, and boring operations. What work-holding device is to be used, a vise or fixture or clamps? After these considerations, computer input can be started. First comes the creation of a JOBPLAN. This JOBPLAN consists of entries such as inch or metric units, machine type, part ID, type of workpiece material, setup notes, and a description of the required tools.

This line of information describes the tool by number, type, and size and includes the

appropriate cutting speed and feed rate. After all the selected tools are entered, the file is saved.

The second programming step is the making of the part. This represents a graphic modeling of the projected machining operation. After selecting a tool from the prepared JOBPLAN, parameters for the cutting operation are entered. For a drill, once the coordinate location of the hole and the depth are given, a circle appears on that spot. If the location is incorrect, the UNDO command erases this entry and allows you to give new values for this operation. When an end mill is being used, cutting movements (toolpath) are usually defined as lines and arcs. As a line is programmed, the toolpath is graphically displayed and errors can be corrected instantly.

At any time during programming, the command SHOWPATH will show the actual toolpath for each of the programmed tools. The tools will be displayed in the sequence in which they will be used during actual machining. If the sequence of a tool movement needs to be changed, a few keystrokes will to that.

Sometimes in CAM the programming sequence is different from the actual machining order. An example would be the machining of a pocket in a part. With CAM, the finished pocket outline is programmed first, then this outline is used to define the ro ughing cuts to machine the pocket. The roughing cuts are computer generated from inputs such as depth and width of cut and how much material to leave for the finish cut. Different roughing patterns can be tried out to allow the programmer to select the most efllcient one for the actual machining cuts. Since each tool is represented by a different color, it is easy to observe the toolpath made by each one.

A CAM system lets the programmer view the graphics model from varying angles, such as a top, front, side, or isometric view. A toolpath that looks correct from a top view, may show from a front view that the depth of the cutting tool is incorrect. Changes can easily be made and seen immediately.

When the toolpath and the sequence of operations are satisfactory, machine ready code has to be made. This is as easy as specifying the CNC machine that is to be used to machine the part. The code generator for that specific CNC machin e during processing accesses four different files. The JOBPLAN file for the tool information and the GRAPHICE file for the toolpath and cutting sequence. It also uses the MACHINE DEFINE file which defines the CNC code words for that specific machine. This file also supplies data for maximum feed rates, RPM, toolchange times, and so on. The fourth file taking part in the code generating process is the TEMPLATE file. This file acts like a ruler that produces the CNC code with all of its parts in the right place and sequence. When the code generation is complete, a projected machining time is displayed. This time is calculated from values such as feed rates and distances traveled, noncutting movements at maximum feed rates between points, tool change times, and so on. The projected machining time can be revised by changing tooling to allow for higher metal removal rates or creating a more efficient toolpath. This display of total time required can also be used to estimate production costs. If more then one CNC machine tool is available to machine this part, making code and comparing the machining time may show that one machine is more efficient than the others.

CAD/CAM

Another method of creating toolpath is with the use of a Computer-aided Drafting (CAD) file. Most machine drawings are created using computers with the description and part geometry stored in the computer database. SmartCAM, though its CAM CONNECTION, will read a CAD file and transfer its geometry represents the part profile, holes, and so on. The programmer still needs to prepare a JOBPLAN with all the necessary tools, but instead of programming a profile line by line, now only a tool has to be assigned to an existing profile. Again, using the SHOWPA TH function will display the toolpath for each tool and their sequence. Constant research and developments in CAD/CAM interaction will change how they work with each other. Some CAD and CAM programs, if loaded on the same computer, make it possible to switch between the two with a few keystrokes, designing and programming at the same time.

The work area around the machine needs to be kept clean and clear of obstructions to prevent slipping or tripping. Machine surfaces should not be used as worktables. Use proper lifting methods to handle heavy workpieces, fixtures, or heavy cutting tools. Make measurements only when the spindle has come to a complete standstill. Chips should never be handled with bare hands.

Before starting the machine make sure that the work-holding device and the workpiece are securely fastened. When changing cutting tools, protect the workpiece being machined from damage, and protect your hands from sharp cutting edges. Use only sharp cutting tools. Check that cutting tools are installed correctly and securely.

Do not operate any machine controls unless you understand their function and what the y will do.

The Early Development Of Numerically Controlled Machine Tools

The highly sophisticated CNC machine tools of today, in the vast and diverse range found throughout the field of manufacturing processing, started from very humble beginnings in a number of the major industrialized countries. Some of the earliest research and development work in this field was completed in USA and a mention will be made of the UK's contribution to this numerical control development.

A major problem occurred just after the Second World War, in that progress in all areas of military and commercial development had been so rapid that the levels of automation and accuracy required by the modern industrialized world could not be attained from the lab our intensive machines in use at that time. The question was how to overcome the disadvantages of conventional plant and current manning levels. It is generally ackonwledged that the earliest work into numerical control was the study commissioned in 1947 by the US governme nt. The study's conclusion was that the metal cutting industry throughout the entire country could not copy with the demands of the American Air Force, let alone the rest of industry! As a direct result of the survey, the US Air Force contracted the Persons Corporation to see if they could develop a flexible, dynamic, manufacturing system which would maximize productivity. The

Massachusetts Institute of Technology (MIT) was sub-contracted into this research and development by the Parsons Corporation, during the period 1949-1951,and jointly they developed the first control system which could be adapted to a wide range of machine tools. The Cincinnati Machine Tool Company converted one of their standard 28 inch "Hydro-Tel" milling machines or a three-axis automatic milling made use of a servo-mechanism for the drive system on the axes. This machine made use of a servomechanism for the drive system on the axes, which controlled the table positioning, cross-slide and spindle head. The machine cab be classified as the first truly three axis continuous path machine tool and it was able to generate a required shape, or curve, by simultaneous slide way motions, if necessary.

At about the same times as these American advances in machine tool control were taking Place, Alfred Herbert Limited in the United Kingdom had their first Mutinous path control system which became available in 1956.Over the next few years in both the USA and Europe, further development work occurred. These early numerical control developments were principally for the aerospace industry, where it was necessary to cut complex geometric shapes such as airframe components and turbine blades. In parallel with this development of sophisticated control systems for aerospace requirements, a point-to-point controller was developed for more general machining applications. These less sophisticated point-to-point machines were considerably cheaper than their more complex continuous path cousins and were used when only positional accuracy was necessary. As an example of point-to-point motion on a machine tool for drilling operations, the typical movement might be fast traverse of the work piece under the drill's position-after drilling the hole, anther rapid move takes place to the next hole's position-after retraction of the drill. Of course, the rapid motion of the slideways could be achieved by each axis in a sequential and independent manner, or simultaneously. If a separate control was utilisec for each axis, the former method of table travel was less esse ntial to avoid any backlash in the system to obtain the required degree of positional accuracy and so it was necessary that the approach direction to the next point was always the same.

The earliest examples of these cheaper point-to-point machines usually did not use recalculating ball screws; this meant that the motions would be sluggish, and sliderways would inevitably suffer from backlash, but more will be said about this topic later in the chapter.

The early NC machines were, in the main, based upon a modified milling machine with this concept of control being utilized on turning, punching, grinding and a whole host of other machine tools later. Towards the end of the 1950s,hydrostatic slideways were often incorporated for machine tools of highly precision, which to sonic extent overcame the section problem associated with conventional slideway response, whiles averaging-out slideway inaccuracy brought about a much increased preasion in the machine tool and improved their control characteristics allows "concept of the machining center" was the product of this early work, as it allowed the machine to manufacture a range of components using a wide variety of machining processes at a single set-up, without transfer of workpieces to other variety machine tools. A machining center differed conceptually in its design from that of a milling machine, In that the

cutting tools could be changed automatically by the transfer machanism, or selector, from the magazine to spindle, or vice versa.In this ductively and the automatic tool changing feature enabled the machining center to productively and efficiently machine a range of components, by replacing old tools for new, or reselecting the next cutter whilst the current machining process is in cycle.

In the mid 1960s,a UK company, Molins, introduced their unique "System 24" which was meant represent the ability of a system to machine for 24 hours per day. It could be thought of as a "machining complex" which allowed a series of NC single purpose machine tools to be linked by a computerized conveyor system. This conveyor allowed the work pieces to be palletized and then directed to as machine tool as necessary. This was an early, but admirable, attempt at a form of Flexible manufacturing System concept, but was unfortunately doomed to failure. Its principal weakness was that only a small proportion of component varieties could be machine at any instant and that even fewer work pieces required the same operations to be performed on them. These factors meant that the utilization level was low, coupled to the fact that the machine tools were expensive and allowed frequent production bottlenecks of work-in-progress to arise, which further slowed down the whole operation.

The early to mid-1970s was a time of revolutionary in the area of machine tool controller development, when the term computerized numerical control (CNC) became a reality. This new breed of controllers gave a company the ability to change work piece geometries, together with programs, easily with the minimum of development and lead time, allowing it to be economically viable to machine small batches, or even one-off successfully. The dream of allowing a computerized numerical controller the flexibility and ease of program editing in a production environment became a reality when two ralated factors occurred.These were:the development of integrated circuits, which reduces electronics circuit size, giving better maintenance and allowing more standardization of desing; that general purpose computers were reduced in size coupled to the fact that their cost of production had fallen considerably.

The multipie benefits of cheaper electorics with greater reliability have result in the CNC fitted to the machine tools today, with the power and sophistication progtessing considerably in the last few years, allowing an almost artificial intelligence(AI) to the latest systems. Over the years, the machine tools builders have produced a large diversity in the range of applications of CNC and just some of those development will be reviewed in V olume Ⅲ。

With any capital cost item, such as a CNC machine tool, it is necessary for a company to undergo a feasibility study in order to ascertain whether the purchase of new plant is necessary and can be justified over a relatively short pay-back period. These thoughts and other circial decisions will be the subject of the next section which is concerned with the economic justification for CNC.

中文部分

机床实践

随着先进科技的硬件变得复杂化，把原料加工成为有用产品的理想的、新的加工手段得到了普遍应用。这已经成为近几年机床加工的发展趋势。先进的机床控制方法和完全不同的材料成形方法还迫使机械设计人员进行前几年还完全没有进行的方向（研究）。

其他科技如电子技术和计算机技术的并行发展，使机床设计者有办法让机床具有超过绝大多数经验丰富的机械师（在普通机床上）所具有的加工能力。

在这个部分我们来看数控机床切削使用的工具。CNC控制器能被用来驱动和控制多种机床和机构。举几个例子，如刳刨机进行木料加工；激光、离子弧、火焰切削、喷水切削钢板；在制造和装配中机器人的控制等。本书的这个部分仅是一般介绍而不能作为专业机床的设计手册。由于计算机能力和容量的巨大增长，机床的控制技术很频繁地发生着变化。在机床控制发展中的精彩部分是在每个先进技术上的使用变得很容易了。

NC的优势

人工操作机床可能有和CNC机床一样的物理特性，例如马力和尺寸，其金属切削原理也是一样的。CNC最大的好处是通过计算机控制机床刀具的运动，CNC控制的机床可能简单得象2刀钻床或复杂得象5刀的加工中心（如图O-1）。两轴的加工机床，其特点是低转速、高马力轴有高进给率，高转速轴允许高效的高速切削刀具如钻石和小直径的刀具的使用（如图O-2）。它的切削刀具是标准的刀具如磨床的刀具、钻子、钻探工具或车刀，这些刀具依赖于所使用的机床型号。切削速度和进给量要象在其他操作机床中一样是正确的。

CNC机床的最大优势来自无错的和快速的可能运动的控制。数控机床不会在一次加工完成后停下来计划下一次的运动，它不会疲劳，它是不中断的机床，机床只有在它切削的时候才有生产性。

当切削过程被适当的进给量和切削速度控制时，时间的节约可以通过快速的进给率来完成。快速进给从60发展到200到400到现在已接近每分1000英寸了。这样高的进给率对在机床工作区的任何人构成了安全威胁。

在CNC机床之前，复杂形状的加工是极困难的。CNC使这些形状的加工制造在经济上是可行的。零件的设计变化通过改变控制机床的程序而相对容易实现。

CNC机床不需要额外的时间和特别的预防就可生产高精度的严格公差的零件。CNC使机床不需要复杂的夹具，这使零件很快被加工从而节约了时间。一旦程序准备好并加工零件，每个零件都将花与第一个一样的时间。这个一致性允许很精确地控制加工成本。数控机床的另一个优势是大量存货的减少，零件可以在需要时再被加工。在传统制造中，为了增加效率，通常一大批零件被同时加工。有了CNC即使一件也能够被经济地加工。在很多情况下，一个CNC机床完成了要建立几台相同传统机床才能做的操作。

CAM和CNC

CAM系统改变了CNC程序员的工作，即从手工编制CNC代码到CNC机床的输出最大值。自从手工CNC机床被一大批厂家生产以来，许多不同的CNC控制单元就被使用了。各个不同的厂家的控制单元使用各个不相同的程序与代码。许多CNC代码语句可被不同的控制器识别。但其间还有众多的区别。为了在有着不同控制器（如FAWC、OKUMA、或DYNAPATH）生产一个可互换的零件，将需要完全不同的CNC代码。每个制造商在不断地提高和更新其CNC控制。这些改进通常包括附加的代码语句在已有代码如何工作上的变化。CAM系统允许CNC程序员在高效的加工过程的建立上浓缩、精选、而不重新学习已改变的代码格式。一个CNC程序员看着一个零件的图纸，并且设计必要的机床操作来制造这个零件（如图O-3）。这个设计包括以下每个因素，从可能使用的CNC机床的选择，到机床的使用选择，再到加工时的零件装夹的选择。CNC程序员必须对这个即将写入程序的CNC机床的能力和局限有一个完全的了解。机床主参数如马力主轴马力、最大转速、工作台的重量、工具的尺寸限制、加工变化能力等只是值得考虑的影响程序的因素中的一些。对程序员要求的另一个最重要领域是制造过程的知识。举例如选择最佳的切削工具来完成零件图上所标的公差和表面光洁度。这个加工过程的程序是吹毛求疵地获得符合的结果。机床极限能力必须考虑全面，这就需要刀具材料，刀具类型，和其推荐应用的知识。一个优秀的程序员将花相当数量的时间来研究关于新的、改进的刀具和刀具材料的快速设计者发表的书籍。通常在切削方面使用两年前的技术的刀具现在就是落后的。新刀具的信息来自手册或刀具制造商的刀具之资料。刀具选择或最佳刀具工作条件的帮助同样可在刀具制造商的软件中获得。例如：Kennametal’s被设计来帮助不同的使用其车间的工厂选择最佳的机床；“TOOCPRO”的另一个很重要的特征是为每个机床选择马力需求等等这些就允许设计者选择一个结合了切削速度、进给率和切削深度等因素的机床。这就胜任于粗选中最佳马力的选择。对于光洁度的加工，零件在加工中最小进给量被选定，接着切削速度直到转速与机床的最佳转速相等时才不变。这就帮助最大提高了机床效率。如果不只一台机床在同时工作的话了解一台机床的功率需求是必要的。

为加工中心使用的软件是ENGERSOLL CUTTING TOOL公司的ACTUAL CHIP THICKNESS。程序被用来计算磨床每次进的给量，特别是在微量的光洁度加工中。ENGERSOLL的“精密分析”软件作为机床刚度和机床力的功能来。在这一点上我们观察一些广泛的设计人员应掌握的规格。现在我们测试CAM系统怎样工作。点控公司（POINT CPNTROLL COMPANY）的SMARTCAM 系统使用接下来的手段：首先设计人员使用一个金属零件模型去加工。这包括的加工方式是------车或磨。接着这个零件图被研究来做成机床加工工序，粗加工或精加工、钻、冲、磨等操作。被使用的装夹夹具是虎钳，抓盘还是卡盘？这些考虑之后，计算机输出就可开始了。首先还是工艺卡的建立。这个工艺卡由各种记录（例如：英制或公制，机床类型、零件卡、切削材料类型、安装记录、和所需要机床的描述

其第二个编程的步骤是零件的制造。这描述了一个所设计机床操作的生动模型。从已准备好的JOBPLAN中选好机床后，切削加工的参数就被编入。对钻床而言，一旦孔的位置

坐标和深度被给出，一个孔就给出现在那点。如果其位置是错的，其撤消命令选择这一记录，并允许你给这个工序新的值。当端面磨时，切削运动通常被定义为弧。当一条直线被编入程序， TOOLPATH就会生动的显示，其错误也可立即被纠正。

在程序运行的任意时刻，命令SHOWPATH会显示当前的刀具轨迹，也会显示刀具在实际加工时的使用顺序。当刀具运动顺序需要改变时，可用一个按键来实现它。

有时，CAM的程序顺序和实际加工的顺序是各不相同的。某部件的孔的加工就是一个例子。首先，在CAM中编译已加工孔的外部轮廓，再把外部轮廓当成粗基准来加工内孔。根据输入切削的宽和深以及完成切削需切去的材料，计算机产生粗切削的加工程序。程序员尝试各种粗基准，以便选出最有效的切削加工方法。由于用不同的颜色代表不同的刀具，所以观察不同刀具的轨迹是很容易的。一个CAM系统可让程序员从不同的角度观察图形，比如说从顶部、正面、侧面或立体图。俯视中正确的刀具轨迹，在正视图中，切削的深度是不正确的，其变化显而易见。

当刀具路径及其顺序定好后，机床的代码应被做好。这和详细指明加工这个部件的CNC 机床一样容易。运行时，指定机床的代码发生器相当于四个不同的键。JOBPLAN文件运行时，表示刀具信息，GRAPHICS文件表示刀具路径和切削顺序。也用MACHINE DEFINE文件表示CNC代码命令。这个文件可提供最大的进给速度、转速、加工时间等等。当代码发生器完成时，加工的计划时间就确定了。这个时间是根据进给速度，运行的距离，两点间在最大进给时间速度下无切削运动的时间，换刀时间等等确定的。这个计划加工时间可通过改变安装后达到更智能的移动速度或创造一种更有效的刀具轨迹来调整。所需的总时间的确定可用来估计生产费用。若不只一个CNC机床可以来加工这工件，制作代码和比较在加工总时间可以表示一个机床是否比另一个机床该更有效，

CAM/CAD

另一个确立刀具路径的方法是借助计算机辅助绘图。大多数的机械绘图使用电脑存储了零件平面图形及其注释。格式化的CAM通过它的CAM CONNECTION，可以读一个CAD文件和转移它的图形到它的轮廓基准中去。这图形可表示零件的外形轮廓、孔等等。程序员仍需准备一个工艺卡，含有所用需要的刀具。但相对于用一排排程序来表示外形，现在刀具只用现有的轮廓来表示即可。另外，使用SHOWPATH功能可以显示每个刀具的路径和他们的顺序。CAD/CAM相互影响的方向的不断探索和发展将会改变他们的工作方式。一些CAD 和CAM程序，如果在相同的计算机上下载，可同时使用一些按键、图纸和程序，使其能相互匹配。

机床周围应该保持清洁，并且无导致绊倒或打滑的障碍物。机床表面不应该被用作工作台。用正确的方法提升重的工作部件，或固定重的切削刀具。启动机床之前，确定工作装置和工件是否安全的固定了。换刀时，保护工件不受伤害，同时保护你的手不被锋利的尖角弄伤。使用锋利的切削刀具时，检查切削刀具是否正确和安全的安装。

直到你理解它们的功能和动作方可操作这台机床。

数控机床刀具早期的发展

今天在机器化大生产领域中千形百态，结构复杂的刀具，起源于一些主要的工业国，开始很简陋。这个领域中，最早的一些研究和发展完成于美国，并记载了UK关于数控发展方面的贡献。第二次世界大战后的一个主要问题是，商业和军队迅速发展，在劳动力密集的加工中，现代工业界所需的自动化与精确度不可获得。问题是怎么样来克服来自常规的加工方法和手工制作的不足。通常认为，关于数控的研究是1949年美国政府的授权。结论就是致使美国空军与Parsons公司签约，让他们找到一种灵活的、有力的制造系统，它能扩大生产。麻省理工大学开始进入研究，而Parsons公司使之发展起来。在1949—1951期间，他们联合发明了一种可适合多种刀具的第一个数控系统。辛辛那提机床刀具公司把他们的一个28英寸的“Hydro—Tel”军用机床改装为三轴自动机床，改变了它们的外部轮廓。在控制桌面位置，典型的机床是三轴连续曲线的机床刀具，它能产生一个所需要的形状或曲线，可能的话，通过一个连续的滑移实现。

与美国机床刀具控制发展的同时，UK中的ALIFRED Herber产生了第一台NC机床。1956年更可靠的曲线路径控制系统开始使用。几年后，在USA与欧洲开始了更深远的研究。早期数控的发展主要为了航空业，它需要切削加工复杂的几何形状，如机件部件与涡轮机叶片。在航空所需要的复杂的控制系统发展的同时，点与点控制器发展起来，更广泛的用于加工当中。较简单的点与点机床比复杂的连续路径的同类产品便宜一些，并在用于需要精确定位的加工中。作为一个钻操作的机床刀具的点至点移动例子，典型的运动是快速经过在钻主轴下的工件，钻空后，迅速的滑移的运动可能过每轴以连续且独立的方式获得。分开的控制可由每轴完成，在早期的点到点机床中，选取路径不很重要，但它必须避免在获得多需要精度中所产生的冲击。所以，趋势下一点的方向必须是相同的。最早的这些点到点机床长循环的球行螺丝钉，这就意味着那些运动必须很缓慢，移动中遇到的冲击不可避免，关于这个问题下章有更详细的叙述。

早期的NC机床，主要的在磨床基础发展起来的，控制的概念主要用于形成，打孔，磨削以及后来的大量的另外的机床刀具。19世纪50年代以来，流件滑动在高精度的机床中常被结合使用，它在某种程度上克服了常规滑轨相关的问题，然而平均输出导轨的不精确度对刀具要求更高并增加了它的控制特性。

加工中心的概念是早期工作的结果，它允许机床在一个安装上对工件进行多种加工，而不需要把工件转移到另外的刀具下。一个加工中心不同于一个磨床，相互要在于它能利用转移装置和分离器自动的把切削刀具从刀具库中转移到主轴上。用这种方式，自动换刀特性使这加工中心高效的加工多种部件，用新刀具代替旧刀具或预选刀具，使得现今的加工过程循环操作。

在19世纪60年代中时，一个UK公司，Molins介绍他们独特的“系统24”意思是一天能加工24小时。它可被认为是系列但作用刀具通过计算机上控制的运输系统连接起来

的复合机床。这个运输装置让工件放在托盘上送至所需的机床刀具下。这是早期情形，是值得钦佩的。灵活制作系统方面尝试都失败了，它的主要短处是仅仅一小部分的零件种类可随时加工，而更少的工件需要完成于它相同的操作。事实上它的利用水平很低，机床刀具昂贵会导致加工频繁时的“颈瓶”现象，于是进一步限制了整个操作。

13世纪70年代初中叶，是机床刀具控制器变革时期，这个时期，CNC成为了一个现实。新的控制器的产生便使公司可通过改变程序改变了一个工件外形。微型技术的发展，可成功的加工一批或一个2全件。当两个相关的因素存在后，在一个生产环境中，让CNC 实现灵活且轻松的编程的梦想变成为现实。这些现实是：

集成电路的发展，它减少了电路的尺寸，使得维护便利且有利于设计的标准化。

计算机的体积减小，从而它的生产费用也极大的降低。价格便宜，性能稳定等多种优点使得今天的CNC安装在机床刀具上。随着它的不断发展成熟，使在高级的CNC系统上可安上人工智能。这些年来，刀具制作者已经制作了多种多样的刀具可用在CNC系统上，其中的一部分在第3册中将被讨论。

由资金耗费项目上的考虑，就CNC机床刀具而言，为了明确新计划是否必要或证明在短期内实现资金回收，一个公司必须进行可行性分析。这些想法及重要的决定将会成为考虑CNC系统经济性调整问题的主题。