A special case of this cam is constant lead, where the position of the follower is linear with rotation, as in a lead screw.The purpose and detail of implementation influence whether this application is called a cam or a screw thread, but in some cases, the nomenclature may be ambiguous.However, the most common type is in the valve actuators in internal combustion engines.
The most common type has the follower ride in a slot so that the captive follower produces radial motion with positive positioning without the need for a spring or other mechanism to keep the follower in contact with the control surface.
Face cams may provide repetitive motion with a groove that forms a closed curve, or may provide function generation with a stopped groove.
Cams used for function generation may have grooves that require several revolutions to cover the complete function, and in this case, the function generally needs to be invertible so that the groove does not self intersect, and the function output value must differ enough at corresponding rotations that there is sufficient material separating the adjacent groove segments.
A face cam of this type generally has only one slot for a follower on each face.
In some applications, a single element, such as a gear, a barrel cam, or other rotating element with a flat face, may do duty as a face cam in addition to other purposes.