The proper machining sequence of the main surface of the valve accessories and other machined surfaces can streamline the machining, improve the quality and reduce the cost, and the machining sequence of the parts is also based on the division of the process and the positioning of the reference. In the machining process, the following basic principles should be followed:
The first is the principle of “first coarse and then fine”, that is, the roughing according to the first, followed by the semi-finishing, then the finishing sequence, and finally the order of the main surface. In addition to the reference plane, the higher the precision and the smaller the surface roughness Ra, the lower the surface should be placed at the end of the process to prevent scratching or the valve accessories being squeezed when working in front of the work to affect the accuracy.
The second is the principle of “first master and second time”, that is, the main surface of the valve accessories is first processed, and the secondary surface is processed after reaching a certain precision. As well as the principle of "first face and back hole", the plane positioning is much more stable than the hole positioning. Finally, the principle of “reference first” is to process the reference surface and post-process other surfaces in each processing stage.www.dmgcastings.com