在数控加工前，必须根据工件的形状、尺寸精度等将工件各关键点坐标的位置准确无误地确定在平面上，通过分析这些点的坐标尺寸及相互关系，并用机床所能接受的指令编制出程序，作为信息输入机床，使其加工工件。但有大量工件，其尺寸精度要求高，形状复杂，APT编程时，在XOY平 Before NC machining, the position of each key point coordinate of the work piece must be accurately determined on the plane according to the shape and dimensional accuracy of the work piece. By analyzing the coordinate dimensions and correlations of these points and using the instructions accepted by the machine tool, Program, as the information entered into the machine tool to make the workpiece. However, a large number of workpieces, which require high dimensional accuracy, complex shape, APT programming, the XOY level