Analysis of the influence of CNC machining technology and programming on the quality control of parts（2）

(1 Determine reasonable programming data The influence of NC programming on machining accuracy mainly comes from the determination of the programming origin, data processing, trajectory fitting, and machining route selection.

1. Determining the programming origin The programming coordinate system is generally determined by the programmer according to the processing characteristics of the part and the part drawing. The selection of the programming origin directly affects the machining accuracy of the parts. The most fundamental principle for determining the programming coordinate system is that the programming benchmark, design benchmark, and process benchmark are unified, so as to minimize errors caused by dimensional tolerance conversion.

2. Data processing during programming The data processing during NC programming has a direct impact on the machining accuracy of the contour trajectory. The more important factors are the calculation of unknown programming nodes and the conversion of programming dimension tolerance zones.

(1) Some CNC systems can automatically calculate node coordinates based on known contour geometric conditions, but some CNC systems must calculate them manually. The biggest problem encountered when manually calculating the coordinate values of unknown nodes is that the calculation accuracy has been verified through a lot of verification, and sometimes the manual calculation results and the computer axis calculation results will differ by 0.01-003 mm. In order to improve the accuracy of manual calculation, the author recommends: ①The intermediate data of manual calculation (including the angle value should be kept at least 4 decimal places (take a CNC machine tool with a pulse equivalent of 0.001 mm as an example). If you use a calculator to calculate, you should try to keep all decimals. ②The rounding of the programming size should be based on the pulse equivalent of the CNC machine tool. The pulse equivalent is the minimum setting unit of the CNC machine tool and also the minimum control unit of the CNC machine tool. For example, the pulse equivalent of the CNC machine is

0.001 mm, the final calculation result should retain 3 decimal places.