【正文】 p 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 bees important.In the traditional processing, for milling machining processes, plane monly, add a few auxiliary support to prevent due to the distortion caused by cutting force influence, because highspeed cutting machining precision cutting force, so, no need additional support monly.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 , 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 highspeed machining cutting force and deformation of more than 30% reduction processing, generally remend that don39。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 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.傳動軸凸緣叉夾具的設(shè)計凸緣叉成組加工要根據(jù)分組結(jié)果及選定的機(jī)床型號進(jìn)行成組夾具設(shè)計，成組夾具是實現(xiàn)成組加工的有利保證，分組再合理，如果設(shè)計不出成組夾具或設(shè)計的成組夾具調(diào)整不方便，成組加工也不能順利實現(xiàn)。機(jī)床夾具的首要任務(wù)是保證加工精度，特別是保證被加工工件的加工面與定位面以及被加工表面相互之間的位置精度。使用夾具后，這種精度主要靠夾具和機(jī)床來保證，不再依賴于工人的技術(shù)水平。其次是提高勞動生產(chǎn)率，降低成本，使用夾具后可減少劃線、找正等輔助時間，且易于實現(xiàn)多件、多工位加工。在現(xiàn)代機(jī)床夾具中，廣泛采用氣動、液壓等機(jī)動夾緊裝置，可使輔助時間盡一步減少。成組夾具是在成組技術(shù)原理指導(dǎo)下，為執(zhí)行成組工藝而設(shè)計的夾具，與專用夾具相比，成組夾具的設(shè)計不是針對某一零件的某一工序，而是針對一組零件的某個工序，即成組夾具要適應(yīng)零件組內(nèi)所有零件的在某一工序的加工。設(shè)計中的重點和難點。工件在機(jī)床上加工時，首先要使工件在機(jī)床上或夾具中占有某一正確位置，這就是定位，為了防止加工過程中切削力或其他外力破壞這一正確位置，還必須將工件夾牢壓緊，這就是夾緊，工件定位與夾緊的過程就稱為工件安裝。由于工件定位而產(chǎn)生的誤差稱為定位誤差，由于工件夾緊變形而產(chǎn)生的誤差稱為夾緊誤差。定位誤差和夾緊誤差合稱為工件安裝誤差.由于這21種零件全部為薄壁件，所以確定夾具方案的關(guān)鍵便是將夾緊變形控制在最小。而夾緊變形的控制不能靠操作者來實現(xiàn)，過去殼體類零件在加工中靠小而可靠的夾緊力來減少夾緊變形，這樣難免會產(chǎn)生不良品。國內(nèi)在引進(jìn)產(chǎn)品技術(shù)的同時，不太注重加工技術(shù)的引進(jìn)，生產(chǎn)批量不同、加工工藝不同、使用設(shè)備不同，那么所需要的夾緊定位點則不同，在引進(jìn)的同時必須消化吸收，所以在此次工藝設(shè)計過程中，按夾緊定位的實際需要，在毛坯中增加統(tǒng)一的定位及夾緊點。定位點的選擇原則不可能偏離六點定位的原則，但在選擇的時候必須注意。I、確定平面的3點必須形成穩(wěn)定支撐，即三角形的重心靠近工件的中心限制防轉(zhuǎn)自由度的2點距離越遠(yuǎn)，定位越準(zhǔn)確。在零件中，最關(guān)鍵的工序是第一道工序— 平面加工。根據(jù)生產(chǎn)批量及零件的結(jié)構(gòu)及精度，有的零件平面單獨(dú)加工，有的零件平面及孔在一道工序中加工。平面加工質(zhì)量的好壞，直接導(dǎo)致整個工藝的成敗。面加工不良，主要是平面度不良，平面度超差會在下道工序的加工中產(chǎn)生較大的夾緊變形，在夾緊狀態(tài)，零件精度會在公差之內(nèi)，松開之后，夾緊變形恢復(fù)，此時零件精度就會發(fā)生變化，而且具有規(guī)律性。面加工不良由夾具產(chǎn)生的原因主要有兩個:定位選擇不合理。夾緊點不合理。所以，面加工的夾具設(shè)計成為重中之重。在傳統(tǒng)加工中，對于有銑削平面加工的工序，一般都增加幾個輔助支撐，防止由于切削力造成的工件變形影響加工精度，由于高速切削切削力減小，所以，一般不再需要輔助支撐。在面加工中，一定要考慮到加工工藝的靈活性，能采用車加工的就不要去銑削。在定 位、夾緊點的選擇上注意以下幾個問題:由3個支撐點形成一個支撐平面來支撐工件，這樣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，并且支撐點與夾緊點應(yīng)上下重合，避免形成彎矩引 起工件變形。由于夾緊引起的工件彈性變形，在松開夾緊后回彈，會造成平面度超差 ，這是引起平面度超差的主要原因。支撐點和夾緊點最好是球面，保證各處是點接觸，否則會因為毛坯平面的撓曲變形造成 夾緊變形。這個變形同樣會造成平面度超差。當(dāng)工件的上表面無法夾緊時，可采用側(cè)面夾緊，如果被夾緊的零件是盒形件，一定在工件內(nèi)增加塞塊，用以避免夾緊變形。此種夾緊方式最好不要采用，或者采用其它工藝方法加工平面，或者要求設(shè)計者在設(shè)計中增加夾緊點。 由于高速切削加工切削力降低30%以上，減少加工變形，一般建議不必增加輔助支撐便可保證加工精度。2個限制轉(zhuǎn)動自由度的定位點，距離盡可能遠(yuǎn)，如果毛坯有預(yù)注孔，用2個預(yù)注孔采用彈性圓錐銷定位是最簡單的定位方案。成組夾具的設(shè)計，在考慮上述問題的同時，還需要考慮多種零件采用一套夾具加工，而且品種更換時間要在短時間之內(nèi)完成。所以夾具的設(shè)計必須考慮快換的問題。該夾具是典型的六點定位原則的夾具，夾緊采用液壓式夾緊。該夾具定位采用點定位形式，接觸面近可能小，夾緊同樣采用點接觸，保證定位點與夾緊點在同一條線上，該精度無論從后續(xù)加工定位的角度還是從使用的角度都能很好的滿足要求。另外，在零件加工過程中，對于某一工序而言，是否使用夾具，使用什么類型的夾具，以及使用什么檔次的夾具，都要在夾具設(shè)計前必須加以認(rèn)真的考慮。除了從保證加工質(zhì)量的角度考慮外，還應(yīng)做經(jīng)濟(jì)性分析，以確保所設(shè)計的夾具在經(jīng)濟(jì)性上合理。值得下