Dynamically compensated cams for rigid cam-follower systems with fluctuating cam speed and dominating inertial forces

Abstract

Traditionally, cam-follower systems are designed by assuming a constant camshaft speed. Nevertheless, all cam-follower systems, especially high-speed systems, exhibit some camshaft speed fluctuation (despite the presence of a flywheel) which causes the follower motions to be inaccurate. The paper therefore proposes a novel design procedure that explicitly takes into account the camshaft speed variation. The design procedure assumes that (i) the cam-follower system is conservative and (ii) all forces are inertial. The design procedure is based on a single design choice, i.e. the range of camshaft speed variation, and yields (i) cams that compensate for the inertial dynamics for any period of motion and (ii) a camshaft flywheel whose (small) inertia is independent of the period of motion. A design example shows that the cans designed in this way offer the following advantages, even for non-conservative, non-purely inertial cam-follower systems: (i) smaller flywheel, (ii) more accurate follower motions, (iii) lower motor torques and (iv) a camshaft motion spectrum that is easily and robustly predictable.