Editing Cam (mechanism) (section)

== Face cam ==
A '''face cam''' produces motion by using a follower riding on the face of a disk. 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. 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.

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 [[Inverse function|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 common form is the constant lead cam, where the displacement of the follower is linear with rotation, such as the scroll plate in a [[Scroll chuck#scroll chuck|scroll chuck]]. Non-invertible functions, which require the groove to self-intersect, can be implemented using special follower designs.

[[image:Sash lock.png|thumb|Sash window lock, traditional cam style, for double-hung sash window]]
A variant of the face cam provides motion parallel to the axis of cam rotation. A common example is the traditional [[sash window]] lock, where the cam is mounted to the top of the lower sash, and the follower is the hook on the upper sash. In this application, the cam is used to provide a mechanical advantage in forcing the window shut, and also provides a self-locking action, like some [[Worm gear#Direction of transmission|worm gears]], due to friction.

Face cams may also be used to reference a single output to two inputs, typically where one input is the rotation of the cam and the other is the radial position of the follower. The output is parallel to the axis of the cam. These were once common is mechanical [[Analog computer|analog computation]] and special functions in control systems.<ref>{{cite book
| author = Bomar, Null, and Wallace
| year = 1996
| title = Gunners Mate 1 & C NAVEDTRA 14110
| pages = 4–1
| publisher = Naval Education and Training Professional Development and Technology Center
| url = https://www.scribd.com/doc/7824710/US-Navy-Course-NAVEDTRA-14110-Gunners-Mate-1-C}}</ref>

A face cam that implements three outputs for a single rotational input is the stereo [[phonograph]], where a relatively constant lead groove guides the stylus and tonearm unit, acting as either a rocker-type (tonearm) or linear (linear tracking turntable) follower, and the stylus alone acting as the follower for two [[orthogonal]] outputs to representing the audio signals. These motions are in a plane radial to the rotation of the record and at angles of 45 degrees to the plane of the disk (normal to the groove faces). The position of the tonearm was used by some turntables as a control input, such as to turn the unit off or to load the next disk in a stack, but was ignored in simple units.