Our factory has developed a processing project for cold-pressed elbows. In the mold manufacturing, some rings need to be processed as the punch of the mold. In the processing of the ring, the quality cannot be guaranteed. For this reason, we have designed a horizontal type. The device for turning the ring on the lathe solves the production problem. 1. The workpiece shown in the process analysis diagram is a sketch of the part that needs to be turned out in the mold part. During the trial processing, we use the traditional method of turning the part: (1) using a round head knife and using two-hand control method, combined The light quality of the forming surface is detected, and the processing quality cannot be guaranteed. (2) Using the master device: Considering that the semi-circular part has the smallest curvature at the near chuck (close to 0°) and the closest to the tailstock (close to 90°), the spherical surface is divided into multiple sections and the turning path is used. It's hard to coincide with the adjustment,