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 iformation device.Accordingly,the goal of the designers is to build a program,establish tbmocus 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 systemn is observed.
No one is sure where and how cams got their start.The Sanskrit(Indo-Iranian)
term Jambha (cog.””peg,”or”looth”)may indicate the geographic area in which they had their beginnings,and so may the Teutonic”Kambr”(toothed instrumnent),which relers 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 modem design cam applicd 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 lo computer-aided design and computer-aided manufacturing.Giraphic
workstations enable the design engineer to oplimize the motion and geometry of a cam
mechanism and also to incorporale the kinematic and dynamic performance requirements
necessary over the entire range of operating speeds.In the manufactunng proccess,net-
worked numerically controlled(NC)machines receive digitized geometne data from a
CAD system.The downloaded file of cam coordinate data is forwarded direetly 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.