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396 CAM DESIGN HANDBOOK

12.5 SUMMARY

We conclude the chapter with a summary of both theoretical and practical design consid-
erations for high-speed cam-follower performance.
• Vibrations in dynamic cam-follower systems are primarily due to the compliance in the
system.
• Vibration may also be the result of other practical factors, i.e., errors in fabrication, worn-
out (old) machine parts, misalignment in assembled parts, and imbalance of parts. Back-
lash should be minimized. Preloaded bearings may sometimes be applied and lubrication
systems should be selected carefully for optimum performance.
• An elastic follower with a rigid camshaft in general can employ a single-degree-of
freedom model with impunity.
• The elastic follower with a rigid camshaft model presents the transient vibratory state
for important primary and residual vibrations to be studied; see Chap. 13.
• The elastic camshaft presents a more complicated mathematical nonlinear relationship.
The models of this cam-follower include the closed-track and open-track systems.
• Choose the lubricant properly for compatability in the system.
• Proper choice of cam curves (acceleration curve continuity) are the modified sine, mod-
ified trapezoidal, and polynomial curves. These will minimize the effect of follower
output, linear system, and cam drive nonlinear vibrations. The inertia load of the closed-
track model produces vibrations that are twice the frequency of the modes of the open-
track. Also, the elastic camshaft may produce vibratory resonant couple of the cam input
and the follower system to produce difficulties.
• Excessive noise may accompany vibrations in cam-follower systems. This may be the
result of a waviness error in the cam profile fabrication.
• For automotive camshaft (valve gear) optimization, performance proprietary software
exists in all manufacturers. In App. D the designer will find a comprehensive listing of
available software for design, manufacturing, and engine performance. Some of the
camshaft studies are: cam profile determination, cam surface hertzian stresses, and har-
monic analysis for spring surge and valve bounce.

REFERENCES

Ardayfio, D., “Dynamics of High-Speed Cam Mechanisms with Damped Flexible Followers Driven
by Flexible Camshafts,” ASME paper 76-DET-69, 1976.
Baratta, F.I., and Bluhm, J.I., “When Will a Cam Follower Jump?” Product Engineering, 25: 156–159,
July 1954.
Barkan, P., and McGarrity, R.V., “A Spring-Actuated, Cam-Follower System: Design Theory and
Experimental Results,” Transactions of the ASME, Journal of Engineering for Industry, Paper No.
64-Mech-12, 1964.
Bloom, D., and Radcliffe, C.W., “The Effect of Camshaft Elasticity on the Response of Cam Driven
Systems,” ASME paper 64-Mech-41, 1964.
Chen, F.Y., “Analysis and Design of Cam-Driven Mechanisms with Nonlinearities,” Journal of Engi-
neering for Industry, pp. 685–694, 1973.
Chen, F.Y., Mechanics and Design of Cam Mechanisms, Pergamon Press, N.Y. 1982.