According to follower movement

The motions of the followers are distinguished from each other by the dwells they have. A dwell is the zero displacement or the absence of motion of the follower during the motion of the cam.

Cams are classified according to the motions of the followers in the following ways:

1. Rise-Return-Rise (R-R-R)

In this there is alternate rise and return of the follower with no periods of dwells [Fig. (a)]. Its use is very limited in the industry. The follower has a linear or an angular displacement.

2. Dwell-Rise-Return-Dwell (D-R-R-D)

In such a type of cam, there is rise and return of the follower after the dwell

[Fig. (b)]. This type is used more frequently than the R-R-R type of cam.

3. Dwell-Rise-Dwell-Return-Dwell (D-R-D-R-D)

It is the most widely used type of cam. The dwelling of the cam is followed by rise and dwell and subsequently by return and dwell. In case the return of the follower is by a fall. The motion may be known as Dwell-Rise-Dwell (D-R-D).