Motion-curve synthesis and geometric design of globoidal cam mechanism with intermittent variable speed

A design procedure for increasing the performance of an intermittent globoidal cam mechanism is presented. The proposed procedure is based on the synthesis of roller-follower turret motions at two different speeds to lower the inertia effect caused by the start/stop behaviour of the intermittent mechanism. The motion curves in a globoidal cam mechanism with an intermittent variable speed are defined by non-parametric rational B-splines to increase the transport capability. There are four key techniques to design a cam mechanism: the first is to construct the cam profile by using the volume swept method, the second is to synthesize the motion curve of a turret by using a rational B-spline curve on velocity control, the third is to analyse the mechanical properties of cam by using the geometrical vector method, and the last is to plan an NC programme and to estimate the performance of five-axial precision machining. Four types of motion curves with similar geometric properties are used and the rational B-spline has better dynamic properties than the other three curves. The systematic design approach proposed for a globoidal cam mechanism with an intermittent variable speed is to improve its performance, to upgrade effectively the function of the indexing device, and to increase the production speed of industrial automatic conveyance.