Cutter Location Generation Method for Improving Feedrate and Machining Accuracy Based on Control Characteristics of Machine Tool

Abstract

All types of NC machine tool interpolation are fundamentally based on linear interpolation, using the minimum interpolation unit of the drive. However, linear interpolation causes issues when machining curved surfaces, such as the feedrate not reaching the command feedrate and fluctuations occurring unexpectedly. These are mainly due to the NC interpolation process, and feedrate limiters. In addition, linear interpolation also decreases machining accuracy through inner cornering errors which are caused by acceleration and deceleration. Finally, it also lowers surface quality, by causing tatami patterns during zigzag cutting, due to differences in the locations of acceleration and deceleration in the forward and backward paths. Thus, in order to solve such problems, a method of generating cutter location data with consideration to the machine tool control characteristics, which are the NC sampling time, the feedrate limiters, and acceleration and deceleration, is proposed. The effectiveness of the proposed method is confirmed by simulations and experiments. Compared with a commercial CAM system, the proposed method increases the feedrate, smoothes acceleration and deceleration, and reduces the cutting time by approximately 50%. The proposed method also improves the surface quality and eliminates tatami patterns.