Precision is mainly used to produce product grade, machining precision and machining tolerance are used to evaluate the geometrical parameters of machining surface. However, the actual parameters obtained by any processing method are not accurate. According to the function of the part, the machining accuracy can be guaranteed as long as the machining error is within the tolerance range required by the part drawing. Machining accuracy refers to the actual geometric parameters (size, shape and position) of the machined parts.

First, programming skills. Nc programming is the basic work of NC machining. The workpiece processing program of CNC lathe directly affects the machining accuracy and efficiency behind the machine tool. Proficiency in the use of native programs can reduce the cumulative error of CNC systems. And flexible use of main programs and subroutines.

1, flexible use of the main program and subroutine. In the processing of complex die, it is usually processed in the form of multi-die. If there are several same shapes on the mold, the relationship between the main program and the subroutine should be flexibly used, and the subroutine should be repeatedly called in the main program until the machining is completed. It can not only ensure the consistency of processing size, but also improve processing efficiency.

2. Reduce the cumulative error of numerical control system. Incremental programming is generally used to program artifacts. It is referenced by the previous processing. In this way, the continuous execution of multi - segment programs will inevitably produce certain cumulative errors. So when programming, try to program with patterns, so that each block is an artifact. The origin as a reference can reduce the cumulative error of nc system and ensure the machining accuracy.

Second, tool selection and correct installation. Whether numerical control machining or ordinary machining, the tool is directly applied to the workpiece, so the selection and installation of the tool is a very important factor of machining accuracy and workpiece surface quality. In particular, the workpiece is processed in the CNC machining center, and the tool is stored in the tool library in advance. After processing, can not be replaced at will. So the general principle of tool selection is: easy installation and adjustment, good rigidity, durability, high precision.

Three, reasonable choice of cutting amount. The determination of cutting dosage is an important part of NC machining process. Its size is an important parameter of machine tool main motion and feed motion. It has important influence on machining accuracy and tool wear of workpiece. The choice of cutting quantity includes cutting speed, cutting back quantity and feed quantity. The basic selection principle is: rougher machining requires greater cutting depth, in order to reduce the number of qualified, improve workpiece productivity; Finish machining usually uses smaller cutting depth to achieve higher surface quality.