CNC parts processing

The selection principle of the processing method is to ensure the processing accuracy and surface roughness of the processed surface. Since there are generally many processing methods to obtain the same level of accuracy and surface roughness, in the actual selection, the shape, size and heat treatment requirements of the parts must be fully considered. For example, boring, reaming, grinding and other processing methods for IT7 precision holes can meet the accuracy requirements, but the holes on the box are generally boring or reaming, rather than grinding. Generally, reaming is selected for small-sized box holes, and boring should be selected when the hole diameter is larger. In addition, the requirements for productivity and economy, as well as the actual conditions of the factory's production equipment, should also be considered.

When machining CNC parts on CNC machine tools, there are generally two situations.
The first case: there is a part pattern and a blank, and a CNC machine tool suitable for processing the part should be selected.
The second situation: There is already a CNC machine tool, and it is necessary to select parts suitable for processing on the machine tool.
In either case, the main factors to be considered are the material and type of the blank, the complexity of the contour shape of the part, the size, the processing accuracy, the number of parts, and the heat treatment requirements. In summary, there are three points:
① It is necessary to ensure the technical requirements of the processed parts and process qualified products.
② Conducive to improving productivity.
③ Reduce production costs (processing costs) as much as possible.

The characteristics of CNC machining put forward two basic requirements for the fixture: one is to ensure that the coordinate direction of the fixture is relatively fixed with the coordinate direction of the machine tool; the other is to coordinate the size relationship between the CNC parts and the coordinate system of the machine tool. In addition, the following four points should be considered:
1) When the batch of CNC parts is not large, modular fixtures, adjustable fixtures and other general fixtures should be used as much as possible to shorten production preparation time and save production costs.
2) Only consider the use of special fixtures in mass production, and strive to have a simple structure.
3) The loading and unloading of CNC parts should be fast, convenient and reliable to shorten the machine stop time.
4) The CNC parts on the fixture should not hinder the machining of each surface of the part by the machine tool, that is, the fixture should be opened and its positioning, and the clamping mechanism components should not affect the tool movement during processing (such as collisions, etc.).

1) It is better to adopt uniform geometric types and dimensions for the cavity and shape of parts. In this way, the tool specifications and the number of tool changes can be reduced, the programming is convenient, and the production efficiency is improved.
2) The fillet size of the inner groove determines the size of the tool diameter, so the fillet radius of the inner groove should not be too small. The manufacturability of the parts is related to the height of the processed contour and the size of the transition arc radius.
3) When the part is milling the bottom plane, the groove bottom fillet radius r should not be too large.
4) A unified reference positioning should be used. In CNC machining, if there is no unified reference positioning, the contour position and size of the two faces after machining will be inconsistent due to the reinstallation of the workpiece. Therefore, to avoid the above problems and ensure the accuracy of the relative position after the two clamping processes, a unified reference positioning should be adopted.