cnc machining factory CNC machining the thickness of the metal layer removed in each process is called the inter-process machining margin. For the external circle and holes and other torsion outside, machining allowance is from the diameter of the discretion, so called the symmetric allowance (i.e. bilateral allowance), that is, the reality of the thickness of the metal layer removed is half of the machining allowance on the diameter. The machining allowance of the plane is the unilateral allowance, which is the thickness of the metal layer removed in reality.
The goal of leaving machining allowance on the workpiece is to remove the machining deviation and outside shortcomings left by the previous process, such as cold hard layer outside the casting, porosity, sand trap layer, forging outside the oxide skin, decarburization layer, outside cracks, internal stress layer and outside roughness after cutting processing. So as to improve the accuracy of the workpiece and the roughness of the outside. The size of the machining allowance has a large impact on the processing quality and production efficiency.
Machining allowance is too large, not only increases the amount of machining labor, reducing productivity, and increase the material, object and power consumption, CNC machining to improve the cost of processing. If the machining allowance is too small, it is not as good as the various shortcomings and deviations of the previous process, but also not as good as the compensation of the process processing clamping deviations, the formation of scrap. The selection criteria is to ensure the quality of the premise of CNC processing, so that the margin as small as possible. Generally speaking, the more finish machining, the smaller the process margin.
To determine the CNC machining sequence, but also to clarify whether the parts to be processed before the pre-processing. Pre-machining is often done by ordinary machine tools. If the blank accuracy is high, positioning is also more reliable, or processing allowance is sufficient and uniform, it can be pre-machining, and directly on the CNC machine tool processing. At this time, according to the rough benchmark accuracy of the blank to consider the division of CNC machine tool processes, can be a process or divided into several processes to complete.