Follower Types and Offset Followers

Follower Types and Offset Followers

The displacement graph specifies the motion. The follower determines how that motion is picked up off the cam, and the cam profile must be constructed for the specific follower it will run against.

Types. A knife-edge follower is the simplest to construct but wears rapidly, so it is mostly a teaching case. A roller follower rolls rather than slides, giving far less friction and wear — the usual industrial choice. A flat (wedge) follower spreads the contact over a face and suits high loads.

Roller followers change the construction. The displacement applies to the roller's centre, so you plot the centre path from the graph and then draw the actual cam profile as a curve tangent to all the roller positions — offset inward by the roller radius. Using the centre path as the profile makes the cam oversize by exactly one roller radius everywhere.

Offset followers do not pass through the cam's centre. Their line of action is tangent to an offset circle of radius equal to the offset, and displacements are set off along that line rather than radially.

Worked example. A 20 mm rise with a 6 mm radius roller: the centre path rises 20 mm, but the cam surface sits 6 mm inside it all the way round.

Core checkpoint: For a roller follower, plot the centre path first and derive the profile from it. The two are different curves.