TABLE OF CONTENTS The dynamic models of cam-follower systems in Chapter 10 demonstrate that the actual motion of any real follower system consists of the motion requested by the cam function plus some dynamic oscillation superposed on the output. This chapter will explore the phenomena of vibration, particularly residual vibrations, in these systems and discuss methods to minimize them.
Consider a double-dwell cam design. Most such applications in production machinery are designed to move the follower to a precise position and then hold it there, absolutely still and in an accurate, repeatable location so that the production operation can be done on the workpiece. In some machines, an end position accuracy of 0.001 or 0.0005 in is required. If the actual motion of the follower during the rise (or fall) does not exactly match the theoretical cam function (assuming no follower bounce), it might not matter as long as the endpoint is reached at the right time and position. However, if the follower is vibrating during the rise because of the dynamics of the system, it will continue to vibrate freely during the dwell. It is this residual vibration that causes problems in respect to workpiece accuracy. Errors in workpiece position during pickup of new parts from feed-rails, insertion of new parts to the assembly, the welding of components, and even automatic inspection operations, etc., can lead directly to an increase in scrap rate. The first three listed cause real scrap. The fourth can cause false scrap by...
