SEED Unit Design - Cam Mechanisms < >

Typical follower motions are dwell-rise-dwell-fall (DRDF) in which the follower is held stationary at both limits of travel and dwell-rise-fall-dwell (DRFD) in which the follower velocity reverses immediately it reaches the maximum displacement. You should identify alternative motions such as ones including a constant-velocity motion or requiring a specific displacement at a given cam angle.

Referring to Figs 2a or 2b, the lift is the total displacement of the follower between extreme limits of travel; the segment angle is the angle of cam rotation corresponding to one complete rise, fall or dwell action of the follower. A motion segment is one such action.

The pitch curve is the locus of the roller centre. The reference circle is the least radius from the camshaft centre to the cam profile corresponding to the inner dwell of the follower. The prime circle radius is the radius of the pitch curve at inner dwell.

Ignoring friction forces as negligible in comparison with those due to the load, inertia and spring forces, the thrust on the follower acts normally to the cam profile through the "point" of contact and intersects the roller centre. It is inclined to the path by the pressure angle, Figure 10.

Fig 6 Disc Cam with Translating Roller Follower