Flat, Wedge and Offset Follower Cams

Flat, Wedge and Offset Follower Cams

CAPS Grade 12 requires cam profiles for followers of any type at any angle. The displacement graph never changes; how the follower touches the cam does.

Flat (mushroom) follower. The follower face is a flat plate. At each position, draw the flat face perpendicular to the follower's line of travel, positioned at the displacement from the base circle. The cam profile is the curve tangent to all those flat faces — an envelope, exactly as the roller profile was tangent to all the roller circles.

The contact point moves. With a flat follower, contact is not on the follower's centre line: as the cam turns, the touch point slides across the face. That is why a flat follower must be wide enough — if the contact point runs off the edge, the mechanism jams.

Wedge follower. A V-shaped face, treated the same way: draw the wedge at each position and take the envelope.

Offset followers. The line of travel does not pass through the cam centre, so displacements are set along a line tangent to the offset circle rather than radially.

Worked example. A flat follower on a steeply rising cam can have its contact point 15 mm off centre at maximum rise. A follower face only 20 mm wide would lose contact entirely.

Core checkpoint: For any non-knife-edge follower, the profile is the envelope of all the follower positions.