The various components in the CNC machining system, including the manufacturing error of the machine tool, tool and fixture, the installation error, and the wear in use directly affect the machining accuracy of the workpiece. In the process, the process system will produce various errors and thus change. The mutual positional relationship between the tool and the workpiece during the cutting motion will affect the machining accuracy of the part. These errors are related to the structural state of the process system and the cutting process. The main factors that cause machining errors are:
1. Machining principle error: The machining principle error is due to the approximate machining motion or the approximate tool contour. Because of the error in the machining principle, it is called the machining principle error.
2. The geometric error of the machine tool: the manufacturing error of the machine tool, the installation error and the wear in use will directly affect the machining accuracy of the workpiece.
3. Tool manufacturing error and wear: Tool manufacturing error, installation error and wear during use are the main factors affecting the machining accuracy of the workpiece, because the cutting edge, the cutting surface and the workpiece, and the chip are generated during the cutting process. Strong friction will cause the tool to wear. When the tool wear reaches a certain value, the surface roughness of the workpiece increases, the color and shape of the chip change, and vibration is accompanied.
4. Fixture error: Fixture error includes positioning error, clamping error, fixture mounting error and tool setting error. These errors are mainly related to the manufacturing and assembly accuracy of the fixture. The position of the workpiece in the fixture is its positioning base and positioning. The degree of cooperation of the components is determined. However, due to the manufacturing errors of the positioning base surface and the working surface of the positioning component, the actual position of the workpiece in the fixture is inconsistent. After the workpiece is processed, the size is inevitably different. The error, the machining error caused by the inaccurate positioning of the workpiece on the fixture is called the positioning error. It includes the reference displacement error and the reference misalignment error. When processing a batch of workpieces simultaneously by using the adjustment method, the essence of the positioning error is the process reference. The maximum amount of variation in the direction of the machining dimension.
5. Reference misalignment error: The machining error caused when the positioning reference does not coincide with the process reference is called the reference misalignment error, and its magnitude is equal to the tolerance of the dimension between the positioning reference and the process reference.
6. Reference displacement error When the workpiece is positioned in the fixture, due to the manufacturing tolerance of the workpiece positioning base surface and the positioning surface of the positioning component on the fixture and the minimum matching clearance, the positioning reference and the limit reference cannot overlap, thus making each workpiece The position is inconsistent, causing errors in the machining dimensions of the part. This error is called the reference displacement error.