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CHAPTER 1

INTRODUCTION

Harold A. Rothbart, D.Eng.

1.1 INTRODUCTION 1 1.6 CAM PROFILE GRAPHICAL LAYOUT 15
1.2 CAM-FOLLOWER SYSTEM CRITERIA 2 1.7 CAM DEFINITIONS 17
1.3 FOLLOWER TYPES 4 1.8 OTHER METHODS THAN CAMS 20
1.4 CAM CLASSIFICATIONS 5 1.9 DESIGN CONSIDERATIONS 21
1.5 CAMS IN TERMS OF FOLLOWER
MOTION 15

1.1 INTRODUCTION

A cam is an element of the cam-follower mechanical system that compels the movement
of the follower by direct contact. The motion of the follower is the result of a program.
Just as a computer is programmed, so is a cam. Thus, the system can be thought of as a
mechanical information device. Accordingly, the goal of the designers is to build a
program, establish the locus of the contact points between the cam and follower, produce
the cam profile coordinates system, and fabricate the cam within an acceptable accuracy.
After all the parts are assembled the performance of the cam-follower system is observed.
No one is sure where and how cams got their start. The Sanskrit (Indo-Iranian)
term Jambha (“cog,” “peg,” or “tooth”) may indicate the geographic area in which
they had their beginnings, and so may the Teutonic “Kambr” (toothed instrument), which
refers to cam mechanisms that have their origin in the wedge (a linear cam) and have been
found in Paleolithic Age relics of about 10,000 years ago. The later construction of the
great pyramids of Egypt also involved the use of the wedge. However, it was the genius
of Leonardo da Vinci that produced a modern design cam applied to a machine for
pumping water.
Cam-follower mechanisms are found in almost all mechanical devices and machines
(i.e., agriculture, transportation equipment, textiles, packaging, machine tools, printing
presses, automobile internal combustion engines, food processing machines, switches,
ejection molds, and control systems, and more recently in micromachines such as micro-
electromechanical systems [MEMS]). Figure 1.1 shows an automobile cam-driven over-
head valve train linkage.
More recently, computer resources, known as CAD/CAM for cams, offer significant
simplification in the design and fabrication of assembled cam and follower systems.
CAD/CAM refers to computer-aided design and computer-aided manufacturing. Graphic
workstations enable the design engineer to optimize the motion and geometry of a cam
mechanism and also to incorporate the kinematic and dynamic performance requirements
necessary over the entire range of operating speeds. In the manufacturing proccess, net-
worked numerically controlled (NC) machines receive digitized geometric data from a
CAD system. The downloaded file of cam coordinate data is forwarded directly to the
machine tool controller, which eliminates the potential human error inherent in older tech-
niques of manufacturing. The accuracy of the cam produced is frequently improved, and
the costs are lowered.

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