Impact of pad conditioning on the bonnet polishing process

Abstract

Pad conditioning is an important process for the improvement of tool removal characteristics by controlling tool surface conditions. This paper presents an experimental investigation, which attempts to reveal the influencing mechanism of pad conditioning on the tool removal characteristics in bonnet polishing process. By assistance of a dynamometer, a microscope, a laser displacement sensor, and a pressure distribution mapping system, multi-comparative group experiments are carried out to establish the correlation of pad conditions, polishing forces, and tool removal characteristic before and after pad conditioning. Through the experiments, three influencing mechanisms are identified: (1) the asperities of the tool surface become smaller and sharper after conditioning, which indicates that the real contact area between the polishing tool and the workpiece reduces, and the coefficient of friction (COF) increases as well, both leading to the improvement of tool removal efficiency; (2) the size of the asperity is determined by the granularity of the conditioner, for which the smaller the conditioner granularity is, the smaller the asperity will be, leading to the decrease of the real contact area; (3) the contour error of bonnet is improved after pad conditioning, so that the periodic amplitude of the polishing forces reduces and the symmetry of the tool influence function (TIF) becomes better. The influencing mechanism identified in this paper can be further served as critical foundation for the investigation on material removal determination through the optimization of pad conditioning process.