Cam

Cam, part of a machine used to provide a repetitive straight-line or back-and-forth motion to a second part, known as the follower. Cams are used to open and close the inlet and exhaust valves of a motor car engine, to index parts of automatic machinery for mass production, and to operate a sequence of control switches in electrical equipment and many other machines. Complex cam shapes may be required to produce a desired motion.

Three types of cams are in common use, the most common being the disc cam illustrated in Fig. a. The cam profile here is cut from a disc mounted on a rotating shaft. The follower can be a flat plate moving vertically in a straight line, or it can be a roller or knife-edge that moves in a straight line or is pivoted. The follower is usually spring loaded to retain contact with the cam. The second type of cam commonly used is the cylinder cam shown in Fig. b, the follower in which is a pivoted roller moving along a groove cut into a cylindrical cam rotor. The third type is the translation cam shown in Fig. c, in which the required profile that defines the motion is cut into a flat plate that moves back and forth. The follower shown in Fig. a is a spring-loaded knife edge that moves up and down. It can be observed from the figures that the motion of the follower can be changed easily, in order to obtain a desired sequence, by altering the shape of the cam profile.