A Cam is a machine component that either rotates or moves back and forth (reciprocates) to create a prescribed motion in a contacting element known as a follower. The shape of the contacting surface of the cam is determined by the prescribed motion and the profile of the follower.

Cam-follower mechanisms are particularly useful when a simple motion of one part of a machine is to be converted to a more complicated prescribed motion of another part, one that must be accurately timed with respect to the simple motion and may include periods of rest (dwells). Cams are essential elements in automatic machine tools, textile machinery, sewing machines, printing machines, and many others. If the follower is not restrained by a groove on the cam, a spring is necessary to keep the follower in contact with the cam.

Cam systems can replace relatively complicated linkages in achieving desirable motion cycles.

In all cam systems it is important that the follower is always in contact and following the motion of the cam. This is achieved in a number of ways including the following.

Cams are made in a variety of forms,including:

Cams followers can be either reciprocating or pivoting.   There are various methods of transferring the motion from the cam to the follower including the following:

The cam follower can be either offset (as shown below) or in line with the cam centre of rotation..

The first stage in designing a cam system is the creation of a displacement diagram... A typical plate cam with an in-line roller follower is shown below with a displacement diagram. This figure shows the following characteristic features.

The diagram below shows a plate cam with a flat face follower showing twelve follower positions..

The diagram below shows a plate cam with an offset roller follower showing twelve follower positions..

The diagram below shows a plate cam with an pivoting follower showing twelve follower positions..

The displacement diagram is a plot of the cam displacement vs the cam angle e.g.    y = f(θ)
It is possible to plot additional graphs as follows

1) The First order Kinematic Relationship

f'(θ) = dy /dθ..

This is a plot of the slope of the displacement graph and thus the rate of movement of the follower.  High values of f'(θ) result in very steep cam slopes with a risk the the follower will jam


2) The Second order Kinematic Relationship

f''(θ) = d²y /dθ²..

This is related to the curvature of the cam. If f''(θ) becomes very large the curvature of the cam approaches zero ( a point). This is highly unsatisfactory as it results in very high contact stresses and consequent wear...