How Are Plane and Cylindrical Cams Milled?

Cams are produced in many forms. Plane cams and cylindrical cams are the two common types.

Milling Plane Cams

Common working curves for plane cams include Archimedean spirals and involutes. They are generally machined on a vertical milling machine by either vertical or inclined milling.

Milling Cylindrical Cams

A cylindrical cam may have a closed curved groove on its outside cylindrical surface, forming a helical-groove cam, or a helical surface on its end face, forming an end-face cam. In small-batch production, cylindrical cams are milled with an end mill on a vertical milling machine. Cam-curve lead is calculated by different methods according to the drawing conditions.

1. This method applies when there is only one working curve or when several working curves have equal leads, the cam outside diameter is large, and the cutter can approach the blank without interference.
2. The end-mill diameter d₀ equals the diameter of the cam follower roller.
3. The change-gear ratio between the dividing-head gear shaft and the table leadscrew is:i = 40P/P_bwhere 40 is the dividing-head worm ratio, P is the table-leadscrew pitch, and P_h is the cam lead. [TO VERIFY: the source formula uses P_b in the denominator but defines P_h as the cam lead.]
4. For plane-cam milling, cutter positioning depends on follower position. For a centered translating follower, align the line joining the cutter and workpiece centers with the longitudinal feed direction. For an offset translating follower, center the cutter and then shift the table by a distance equal to the follower offset, in the same direction as the follower displacement.