Tool path modeling and error sensitivity analysis of crankshaft pin CNC grinding

Abstract

A tool path generation model with parametric four-bar mechanism was established, and the kinematic geometric coordinate data (tool path) were obtained for crankshaft pin computer numerical control (CNC) grinding. The model was based on the envelope principle; the tool path coordinates were generated by solving a special connecting rod curve. The kinematic performance indexes of crankshaft pin CNC grinding comprise the displacement, velocity, acceleration, jerk in x and y directions, and constant angular speed coefficient. Because of the changes in the parameters, three typical submodels were investigated. It was concluded that the two-axis crankshaft grinding is a special case of in-line slider-crank model. Moreover, a constant angular velocity grinding was achieved using the parallelogram model only. A region was established for the parameters, where the three typical submodels showed the best performance. Finally, the error sensitivity analysis based on the motion error model was carried out using numerical simulation. The results indicate that the three motion errors satisfy the principle of linear superposition, the additional y-axis can be used as error compensation, and the accuracy of rotating spindle C is the most important factor for the high precision of crankshaft pin.