# 2 way 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.

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.

A once common, but now outdated, application of this type of cam was automatic machine tool programming cams.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.

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.

Cylindrical cams may also be used to reference an output to two inputs, where one input is rotation of the cylinder, and the second is position of the follower axially along the cam. These were once common for special functions in control systems, such as fire control mechanisms for guns on naval vessels A face cam produces motion by using a follower riding on the face of a disk.

In designing the cam, the lift and the dwell angle Several key terms are relevant in such a construction of plate cams: base circle, prime circle (with radius equal to the sum of the follower radius and the base circle radius), pitch curve which is the radial curve traced out by applying the radial displacements away from the prime circle across all angles, and the lobe separation angle (LSA - the angle between two adjacent intake and exhaust cam lobes).

The base circle is the smallest circle that can be drawn to the cam profile.