Influence of motion error of feed drive systems onto machined surface generated by ball end mill

Abstract

Although glitches due to motion error of the feed drive systems are typically observed on the machined surface, the relationships between the motion error and glitches are not investigated up to now. The purpose of this study is to clarify the influence of motion error of feed drive systems onto machined surface generated by ball end-mill. In order to achieve the purpose, cutting tests and simulation of hemisphere shape are carried out. The cutting tests of hemisphere are carried out with two kinds of tool paths; uni-directional and bi-directional scanning paths. Parameters of the friction compensator of the NC controller are also changed to investigate the influence of motion characteristics of the machine. In addition, a simulation method for machined surface with the dynamic model of feed drive systems is newly developed. As the results of the cutting tests and simulations, it is confirmed that the proposed simulation method can accurately predict the influences of the motion errors and tool paths onto the machined surface generated by a ball end mill. It is also clarified that the both of motion path and motion errors influence the machined surface, because the innermost motion paths to the work piece are copied onto the finished surface. For example, even if a stepwise error exists on the motion trajectories, the error is not copied onto the finished surface when the surface is generated by bi-directional tool paths, although the error clearly copied on to the surface generated by uni-directional tool path.