一、引言 在机械加工过程中,由于加工的需要,在工序图以及工艺卡上要标注一些工序尺寸。工序尺寸往往不是直接采用零件图上的尺寸,而需要另行计算。在决定加工简单件的各工序间余量和工序所达到精度之后,就可由最后一道工序开始,往前推算各工序的尺寸和公差;当制订表面形状复杂 First, the introduction In the machining process, due to the processing needs, in the process diagram and process card to mark some of the process size. Process size is often not directly use the size of the parts drawings, which need to be calculated separately. In determining the processing of simple pieces of each process between the margin and the accuracy of the process, you can start from the last process, forward calculation of the size and tolerance of each process; when the development of complex surface shape