Part refers to a single piece that cannot be separated in machinery. It is not only the basic element of the machine, but also the basic unit in the process of mechanical manufacturing. Its manufacturing process generally does not need assembly process. Such as bearing sleeve, bearing bush, nut, crankshaft, blade, gear, cam, connecting rod body, connecting rod head, etc. For Dalian precision machining, the processing is very strict. The processing procedures include feeding, discharging and so on. There are specific requirements for size and accuracy, such as 1mm plus or minus microns. If the size is wrong too much, it will become waste products. At this time, it is equivalent to reprocessing, which is time-consuming and laborious. Sometimes, the whole processing material will be scrapped, which increases the cost. At the same time, the parts must not be used.