Study on the geometric characteristics of mating surfaces of globoidal cam mechanisms

• Geometric characteristics of globoidal cam surface are analyzed and simulated.
• The asymptotic curves of globoidal cam surface are calculated and simulated.
• Curvatures of asymptotic curves are calculated to verify the surface is not ruled.
• Dupin's indicatrix of globoidal cam and roller surface are calculated and depicted.
• Indicatrix of conformity is employed to analyze contact geometry of cam mechanism.

This work presents a complete and systematic method for the analysis and simulation of geometric characteristics of mating surfaces of globoidal cam mechanisms. Based on the fundamental forms of globoidal cam surface, the asymptotic curves, the principal directions and curvatures, and the Dupin's indicatrix are obtained and simulated. The curvatures of asymptotic curves are calculated to verify whether the cam surface is a ruled surface or not, which is an important issue to determine the machining process of the globoidal cam. In addition, the relationship between the local shapes of the cam surface and the motion periods is presented. The characteristic curves of relative normal curvature at different contact points are depicted and compared as well. Based on the Dupin's indicatrix, the indicatrix of conformity (Dr. Radzevich, 1980s) is first applied to analyze the contact geometry of mating surfaces of globoidal cam mechanism. The indicatrix of conformity in the case of contact of saddle-like surface with convex parabolic-like surface is first discussed here. A globoidal cam mechanism used in automatic tool changer of CNC machines is presented to clarify the outlined methods. The proposed methodology is important for design, manufacture, and contact analysis of globoidal cam mechanisms.