外文翻译---传动轴凸缘叉夹具的设计

附录

Fork Shaft Lugs fixture design

Shell group processing according to the results of the machine and the group chosen type design group clamps, group clamps Realize that the group process, favorable to reasonable design, if no group clamps or design group clamps, convenient adjustment group processing can realize smoothly.

The machine tool's fixture priority is to ensure machining accuracy, especially that of the machining process and positioning surface and processed surface between the position precision. After using this fixture mainly rely on precision tools and fixtures to ensure no longer rely on workers, the technical level. Second is to improve labor productivity, reduce cost, use fixture after is crossed, can reduce the auxiliary time, and easy to implement and multistage process. In modern times, is widely used in the machine tool's fixture etc mobile pneumatic, hydraulic clamping device, can make the assistant time do step.

In the group technology group clamps are under the guidance of the principle, process and design for the implementation of the group, and special fixture Compared with the design group clamps, not for a certain parts of a process, but a group of some parts, Which group clamps to adapt to all parts of the group parts in a process of processing.

Design of the key and difficult.

When the workpiece in machine processing, the first to make workpiece in machine or a fixture in the correct position, it is the location, to prevent the process of cutting force or other forces destroyed the correct position, still must be fastened clamping workpiece, this is the clamping workpiece position and clamping workpiece installation process is called. Due to the workpiece position and orientation error, error called for clamping deformation and the error is called clamping error. Positioning error and clamping workpiece installation error named error.

Because of this all parts for 21 kinds of workpieces, so the scheme is key to determine the fixture clamping deformation control at will The smallest. While clamping deformation control cannot rely on operators to realize in the past shell parts and machining by small and reliable clamping force to reduce clamping deformation, this will inevitably produce adverse product. In the introduction of domestic product technology at the same time, don't

notice the processing technology, especially the shell parts, production batch processing, different, use equipment that needs are different, clamping orientated in the introduction, digestion and absorption and must therefore in the design process, according to the actual needs of clamping positioning in blank, add uniform positioning and clamping point.

The selection principle of orientated may not deviate from the principle of localization, but at the time must note in the selection, I truly, Planar 3 point must form a stable support, namely the gravity of the triangle, near the workpiece center turn against restrictions freedom 2 some farther, the more accurate positioning.

In parts of the shell, the key process is first step - graphic processing. According to the production batch and parts The structure and the precision, some parts processing, some parts of planar alone on a plane and hole machining process. Graphic processing quality directly cause the whole process, the success or failure. Surface processing, mainly is bad, the flatness of the flatness of the next procedure of processing produce larger clamping deformation, clamping, precision parts in tolerance, loosen, clamping displacementrestoring, precision parts will change, and with regularity. Surface processing by fixture causes adverse has two main: 1, the location selection is not reasonable, 2, clamping point is not reasonable. Therefore, the shell parts processing, surface of fixture design becomes important.

In the traditional processing, for milling machining processes, plane commonly, add a few auxiliary support to prevent due to the distortion caused by cutting force influence, because high-speed cutting machining precision cutting force, so, no need additional support commonly.

In the face of processing, must consider the process of flexibility, can use the car is not to milling machining. In clamping point, on the choice of pay attention to the following problems:

1. By 3 strong point to form a support to support workpiece surface, can avoid blank piece of planar degree due to the deviation caused the machined surface flatness, and supporting and clamping point should avoid a moment, and led up distortion. Because of clamping workpiece elastic deformation, loosen the clamping after springback, can cause planar degree, it is super flatness of the main reason.

2. The best point and clamping point is the sphere, ensure all, otherwise, it will point is because the plane deformation caused by torsion blank clamping deformation. The

deformation will also cause planar degree.

3. When the workpiece surface cannot clamping, can use flank clamping, if clamping parts is deduced.and, must increase in the block, to avoid clamping deformation. The clamping way, had better not use or using other techniques, or request processing plane designers in clamping point increase in design.

4. Because of the high-speed machining cutting force and deformation of more than 30% reduction processing, generally recommend that don't add additional support can guarantee machining accuracy.

5. 2 limit rotational degree of freedom, the distance as far as possible, orientated if blank has note hole, 2 (note hole taper pin location using elastic is the most simple positioning scheme.

In the design of the group clamps, considering the problems at the same time, we also need to consider many parts adopt a fixture, and replacing time processing varieties in a short time to finish. So the fixture design must consider quick change. This fixture is typical of six principles of fixture, positioning clamping adopt pneumatic clamping screw. This fixture locating adopts point positioning forms, interface, nearly may also used clamping point, ensure orientated and clamping point in the same line, this fixture milling face results in the plane degrees below, the precision of 0.02 from the Angle of subsequent processing position from the Angle of use or can be very well meet the requirements.

In addition, in parts processing process, for a process, whether to use fixture, use what type of clip What class, and the use of fixture in jig design must be carefully considered before. Besides the machining quality assurance from view, should also do economic analysis to ensure that the design of fixture in the economy.

传动轴凸缘叉夹具的设计

凸缘叉成组加工要根据分组结果及选定的机床型号进行成组夹具设计，成组夹具是实现成组加工的有利保证，分组再合理，如果设计不出成组夹具或设计的成组夹具调整不方便，成组加工也不能顺利实现。

机床夹具的首要任务是保证加工精度，特别是保证被加工工件的加工面与定位面以及被加工表面相互之间的位置精度。使用夹具后，这种精度主要靠夹具和机床来保证，不再依赖于工人的技术水平。其次是提高劳动生产率，降低成本，使用夹具后可减少划线、找正等辅助时间，且易于实现多件、多工位加工。在现代机床夹具中，广泛采用气动、液压等机动夹紧装置，可使辅助时间尽一步减少。

成组夹具是在成组技术原理指导下，为执行成组工艺而设计的夹具，与专用夹具相比，成组夹具的设计不是针对某一零件的某一工序，而是针对一组零件的某个工序，即成组夹具要适应零件组内所有零件的在某一工序的加工。

设计中的重点和难点。

工件在机床上加工时，首先要使工件在机床上或夹具中占有某一正确位置，这就是定位，为了防止加工过程中切削力或其他外力破坏这一正确位置，还必须将工件夹牢压紧，这就是夹紧，工件定位与夹紧的过程就称为工件安装。由于工件定位而产生的误差称为定位误差，由于工件夹紧变形而产生的误差称为夹紧误差。定位误差和夹紧误差合称为工件安装误差.

由于这21种零件全部为薄壁件，所以确定夹具方案的关键便是将夹紧变形控制在最小。而夹紧变形的控制不能靠操作者来实现，过去壳体类零件在加工中靠小而可靠的夹紧力来减少夹紧变形，这样难免会产生不良品。国内在引进产品技术的同时，不太注重加工技术的引进，生产批量不同、加工工艺不同、使用设备不同，那么所需要的夹紧定位点则不同，在引进的同时必须消化吸收，所以在此次工艺设计过程中，按夹紧定位的实际需要，在毛坯中增加统一的定位及夹紧点。

定位点的选择原则不可能偏离六点定位的原则，但在选择的时候必须注意;I、确定平面的3点必须形成稳定支撑，即三角形的重心靠近工件的中心2、限制防转自由度的2点距离越远，定位越准确。

在零件中，最关键的工序是第一道工序—平面加工。根据生产批量及零件

的结构及精度，有的零件平面单独加工，有的零件平面及孔在一道工序中加工。平面加工质量的好坏，直接导致整个工艺的成败。面加工不良，主要是平面度不良，平面

度超差会在下道工序的加工中产生较大的夹紧变形，在夹紧状态，零件精度会在公差之内，松开之后，夹紧变形恢复，此时零件精度就会发生变化，而且具有规律性。面加工不良由夹具产生的原因主要有两个:1、定位选择不合理;2、夹紧点不合理。所以，面加工的夹具设计成为重中之重。

在传统加工中，对于有铣削平面加工的工序，一般都增加几个辅助支撑，防止由于切削力造成的工件变形影响加工精度，由于高速切削切削力减小，所以，一般不再需要辅助支撑。

在面加工中，一定要考虑到加工工艺的灵活性，能采用车加工的就不要去铣削。在定位、夹紧点的选择上注意以下几个问题:

1、由3个支撑点形成一个支撑平面来支撑工件，这样可以避免由于毛坯工件的平面度偏差而造成加工表面的平面度超差，并且支撑点与夹紧点应上下重合，避免形成弯矩引起工件变形。由于夹紧引起的工件弹性变形，在松开夹紧后回弹，会造成平面度超差，这是引起平面度超差的主要原因。

2、支撑点和夹紧点最好是球面，保证各处是点接触，否则会因为毛坯平面的挠曲变形造成夹紧变形。这个变形同样会造成平面度超差。

3、当工件的上表面无法夹紧时，可采用侧面夹紧，如果被夹紧的零件是盒形件，一定在工件内增加塞块，用以避免夹紧变形。此种夹紧方式最好不要采用，或者采用其它工艺方法加工平面，或者要求设计者在设计中增加夹紧点。

4、由于高速切削加工切削力降低30%以上，减少加工变形，一般建议不必增加辅助支撑便可保证加工精度。

5、2个限制转动自由度的定位点，距离尽可能远，如果毛坯有预注孔，用2个预注孔采用弹性圆锥销定位是最简单的定位方案。

成组夹具的设计，在考虑上述问题的同时，还需要考虑多种零件采用一套夹具加工，而且品种更换时间要在短时间之内完成。所以夹具的设计必须考虑快换的问题。该夹具是典型的六点定位原则的夹具，夹紧采用液压式夹紧。该夹具定位采用点定位形式，接触面近可能小，夹紧同样采用点接触，保证定位点与夹紧点在同一条线上，该夹具铣面结果其平面度在0.02以下，该精度无论从后续加工定位的角度还是从使用的角度都能很好的满足要求。

另外，在零件加工过程中，对于某一工序而言，是否使用夹具，使用什么类型的夹具，以及使用什么档次的夹具，都要在夹具设计前必须加以认真的考虑。除了从保证加工质量的角度考虑外，还应做经济性分析，以确保所设计的夹具在经济性上合理。