Cams

The **cam** and **follower** is a device which can convert rotary motion into linear motion (movement in a straight line). A **cam** is a specially shaped piece of material, usually metal or hard wearing plastic, which is fixed to rotating **shaft**. The cam can have various shapes eg. round, oval, heart shaped. A **follower** is a mechanism which is designed to move up and down as it follows the edge of the cam.

Many machines which have moving parts use cams. A good example is the motor car engine which has cams to open and close valves and contact breaker points and operate fuel pumps.

There are several different types of cams but most of these can be placed into two groups, rotary and linear. Rotary cams change rotary motion into reciprocating (backwards and forwards) motion. the cams come in several shapes including egg-shaped and snail cams, these cams are called "lobed cams" because they have additions to the circular shape known as lobes. As the cam rotates, the follower moves accordingly. The exact distance it moves depends on the shape of the cam and this is know as a the **throw**. The movement of the different cams can be described as smooth.

One complete revolution of the cam is called a **cycle**. As the cam rotates there will be one distinct event per revolution for each lobe. The timing of the events will depend on the speed of rotation. Cams have the ability to store information. Another way to look at cams is as the mechanical version of a computer program. The information is stored in the shape of the cam. As the cam turns, the information is retrieved by the cam follower. The follower tracks the movement of the cam's profile (shape) and reproduces the same movement for each cycle.

Testing your cams watch the video! Click to the next page .