Thus, in practice, the points at which lift begins and ends mean that a tangent to the base circle appears on the profile.This is continuous with a tangent to the tip circle.These diagrams relate angular position, usually in degrees, to the radial displacement experienced at that position.Displacement diagrams are traditionally presented as graphs with non-negative values.Face cams may also be used to reference a single output to two inputs, typically where one input is rotation of the cam and the other is radial position of the follower. These were once common is mechanical analog computation and special functions in control systems.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 tone arm unit, acting as either a rocker-type (tone arm) or linear (linear tracking turntable) follower, and the stylus alone acting as the follower for two orthogonal outputs to representing the audio signals.A common example is the camshaft of an automobile, which takes the rotary motion of the engine and translates it into the reciprocating motion necessary to operate the intake and exhaust valves of the cylinders.
A face cam of this type generally has only one slot for a follower on each face.
A once common, but now outdated, application of this type of cam was automatic machine tool programming cams.
Each tool movement or operation was controlled directly by one or more cams.
Here, the cam profile is commonly symmetric and at rotational speeds generally met with, very high acceleration forces develop.
Ideally, a convex curve between the onset and maximum position of lift reduces acceleration, but this requires impractically large shaft diameters relative to lift.
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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.