From DT Online
Cams with complex profiles can be complicated to manufacture, particularly with the type of equipment available in the school workshop. However, if all that is required is to produce a single up and down motion for every revolution on the cam, a circular cam rotating about a point offset from its centre (i.e. eccentric), will often suffice.
Features and Applications
An Eccentric Cam would normally provide the follower with Simple Harmonic Motion - (this can be defined as the projection of a point on the diameter of a circle as it precesses around it with constant angular velocity).
|Eccentric Driven Pump - the red arrows indicate the rotation direction of the eccentric shaft and the
fluid moving direction. The front half of the case is removed.
Click top left to enlarge