The follower separation is a major impediment to the operating speed increase of force-closed cam mechanisms. This problem traditionally is solved by increasing the spring preload or spring rate to enlarge the return force. An alternative approach with variable cam speed is proposed to prevent follower separation and thereby to raise the average operating speed. By properly designing the cam speed to change the follower motion, the critical motion characteristics leading to follower separation can be avoided. The cam speed trajectory is expressed using the Bezier function. A mathematical model is developed for analyzing the cycle time and the critical times of follower separation. Then a design model for optimizing the critical average cam speed without follower separation is developed to specify the design parameters of this trajectory. Two design examples with different cam motion programs are given for demonstrating the feasibility of this approach.

Cam mechanisms are widely applied in automatic production machines. Variable cam speeds provide a flexible tool for adapting the follower motion to the working condition changes. The current study proposes the methods for generating the needed follower motion and adjusting to the required times of periods in the cam motion program. The Bezier function is used to express the cam speed trajectory, whose motion characteristics and boundary continuities are to be decided by the control points. An optimization design model for generating the required motion is then built to specify the control points of this trajectory. Also, the relations are developed that cope with connection continuities and period time managements among the motion periods of a complete cam rotation. Two design examples in component transferring and metal-sheet forming applications are given for illustrating the proposed design approaches.