零件的内曲的加工方法很多，但加工的效率、加工精度、刀具要求、加工质量有较大的区别。在数控车床上利用循环指令进行加工内曲面，降低了加工难度，并有效提高了加工精度和加工效率。本文运用实例，介绍广州数控系统（GSK980TDa）中G71、G72、复合循环指令对内曲面的加工。

There are many ways to process the inner surface of parts, but the efficiency, accuracy, tool requirements and processing quality are quite different. In CNC lathe, circular instruction is used to process inner surface, which reduces the difficulty of machining, and effectively improves the processing accuracy and efficiency. This paper introduces the processing of inner surface by G71, G72 and compound cyclic instructions in Guangzhou CNC System (GSK980TDa).