File:Platecam-B.gif

Positive Motion Cam.

The follower in animated cam engages a groove. Cams of this general form are known as face cams, and their distinctive feature is that the follower is given a positive motion in both directions, instead of relying upon a spring or the action of gravity to return the follower . The follower in this particular case is in the form of a bell-crank lever and is given an oscillating motion. One of the defects of the face cam is that the outer edge of of the cam groove tends to rotate the roller in one direction and the inner edge tends to rotate it in the opposite direction. A certain amount of clearance must be provided in the groove and, as the roll changes its contact from the inner edge to the outer edge, there is an instantaneous reversal of rotation which is resisted, due to the inertia of the rapidly revolving roll; the resulting friction tends to wear both the cam and roll. This wearing action, however, may not be serious when the cam rotates at low speed [source: ISBN 978-0-8311-1029-1].

Model created in Spaceclaim and simulated in SimWise 4D.