A cam mechanism consists of three elements: the cam, the follower (or follower system), and the frame. The follower is in direct contact with the cam. The cam may be of various shapes. The follower system includes all of the elements to which motion is imparted by the cam. This may be connected directly to the follower, or connected through linkages and gearing. The frame of the machine supports the bearing surfaces for the cam and for the follower.

Uses for cams:

The cam mechanism is a versatile one. It can be designed to produce almost unlimited types of motioning the follower. It is used to transform a rotary motion into oscillating motion. On certain occasions, it is also used to transform one oscillating motion into a different oscillating motion.   

Cams are used in a wide variety of automatic machines and instruments. Typical examples of their usage include textile machineries, computers, printing presses, food processing machines, internal combustion engines, and countless other automatic machines, control systems and devices. The cam mechanism is indeed a very important component in modern mechanization.

The most well known use of cams is in car engines. The cam operated valve system ( fig 5-1）can be found in modern car engines and incorporates a number of cams and the valves are opened by cams.

Cams can be conveniently classified into two main groups:

Group a: Cams that impart motion to the follower in a plane in line with the axis of rotation of the cam (as does a cylindrical cam).  Group b: Cams that impart motion to the follower in a plane at 90 degrees to the axis of rotation, as with face or edge cams. Most cams fall into this category.

The cam, as a means of producing a given type of motion, is simple and reasonable to design, provided the simple principles are understood. Another advantage is that, generally, a cam can easily be changed or modified to allow a change of motion, without interfering with the remainder of the mechanism.