The principle of precision metal parts processing, the focus of pure basic level consideration is how to reduce errors and improve accuracy, so the basic principles for selecting essential surfaces are:

First: the principle of benchmark coincidence. The design basis as much as possible should be selected as the positioning basis. Especially in the completion, to ensure accuracy, we should pay more attention to this principle. This can avoid causing position error reference deviation;

Second: the unified principle of benchmarks. Various surface treatments of a unified positioning reference surface should be selected to ensure the position accuracy between the surfaces as much as possible; sometimes the principle of common reference is also followed and repeated processing;

Third: the principle of self-reference. Some small machining allowances and a unified finishing process ensure the processing quality and productivity, and the precision machined surface itself serves as a basic level.

We divide mechanical processing into the following four stages:

One, face before hole

For parts such as box body, bracket and connecting rod, the plane should be processed first and then the hole should be processed. In this way, the holes can be positioned on the plane to ensure the accuracy of the plane and the position of the hole, and the processing of the holes on the plane is convenient.

2. Process the datum surface first

During the processing of the part, the surface as the positioning reference should be processed first in order to provide a precise reference for the subsequent processing as soon as possible. Called "benchmark first."

3. Finishing

The main surface finishing (such as grinding, honing, fine grinding/rolling processing, etc.) should be carried out in the process route stage. The surface finish after processing is above Ra0.9um. A slight collision will damage the surface. In Japan, In Germany and other countries, after finishing processing, you must use flannel for protection. Never touch the workpiece directly with your hands or other objects, so as to prevent the finishing surface from being damaged due to the transfer and installation between processes.

Fourth, divide the processing stage

Surfaces with high processing quality requirements are divided into processing stages, which can generally be divided into three stages: rough processing, semi-finishing and finishing. The main purpose is to ensure the processing quality; facilitate the rational use of equipment; facilitate the arrangement of the heat treatment process; and facilitate the discovery of blank defects.