Excessive machining allowance not only increases the labor of machining, reduces productivity, but also increases the cost of materials, objects, and electricity. CNC machining increases the processing cost. If the machining allowance is too small, it will not be able to eliminate the various shortcomings and deviations of the previous process, nor can it compensate for the clamping deviation during the processing of this process, resulting in waste products. The selection criterion is to make the margin as small as possible under the premise of ensuring the quality of CNC machining. Generally speaking, the more finishing, the smaller the process margin.
When determining the CNC machining sequence, it is also necessary to clarify whether the parts need to be pre-processed before processing. Pre-processing is often done by ordinary machine tools. If the precision of the blank is higher, the positioning is more reliable, or the machining allowance is sufficient and uniform, it is not necessary to perform pre-processing, and directly process it on the CNC machine tool. At this time, the division of CNC machine processes should be considered according to the accuracy of the rough reference of the blank, which can be completed in one process or divided into several processes.
