Abstract: On the basis of previously study on optimization of cam lift fitting, based on the cubic spline curve fitting method, a new method using the odd-even alternative-point interpolation for the lift fitting of cam curve is proposed. The method requires several cycles of interpolation fitting process. Through setting fitting accuracy threshold and importing maximum cycle times, lift fitting error controlling and algorithms termination are realized. Numerical analysis comparison between new methods and parametric cubic spline curve fitting method is conducted by using Matlab programming. The results show that the new method can significantly improve the smoothing degree of the original lift curve and its first order, second order differential. In NC cam grinding process, the continuity of the grinding carriage feed rate and acceleration are improved, meanwhile, the feed shaft flexible impact and the tracking error are reduced. Experiments are accomplished using the results of the approach on TKM120 CNC camshaft grinder. Compared to the process result of cubic parameter spline curve lift fitting, the experimental results show that the new approach can significantly improve the surface quality and the contour accuracy.

Key words: Cam, Cubic polynomial spline, Lift fitting, Odd-even alternative-point interpolation