An analytical method for surface roughness prediction in precision grinding of screw rotors

Abstract

In the process of grinding, rubbing, plowing, and cutting occur successively between abrasive grains and workpiece material as the grinding depth increases. In precision grinding of the screw rotor, small grinding depth is generally introduced, which usually results in plowing. Therefore, it is essential to predict the surface roughness caused by plowing in order to make the process controllable. In this paper, an analytical method for predicting tooth surface roughness of the screw rotor in precision grinding has been proposed. This method takes the following factors into consideration, i.e., distribution law of the grain protrusion heights, variation of grinding depth, velocities and diameters of the screw rotor and grinding wheel at different contact points, and the dressing parameters of grinding wheel. A trajectory projection method has been employed to determine the groove depth and distribution left by the abrasive grains. With the proposed model, the distribution of roughness over the screw rotor tooth surface can be calculated. Verification experiments were conducted with several screw motors produced and surface roughness measured. The comparison results reveal a good agreement between predicted results and experimental results, showing the effectiveness of the proposed method. This study could shed light on the plowing phenomena in precision grinding and could provide great potential in achieving an effective control of the surface roughness.