Cam & Follower Classifications

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Cam & Follower Classifications

Classification of Cams and Followers

There is not a general classification for cam and follower mechanical systems. However, the functional embodiments and functions of each sub-system have relatively few possibilities, which we can classify.

Cam-Profile types

The general shape of the cam is generated by the relative motion of the cam and follower-profile.

Planar:

The cam is a disc, plate, track, groove, conjugate, ramp, slot

Spatial:

The cam is cylindrical, barrel, globoidal

Cam Motion

The modes of cam motion are:

Rotating:

The cam swings back and forth - the cam oscillates

The cam rotates continuously

The cam moves progressively (rare)

Translating:

The cam slides back and forth - the cam reciprocates

The cam moves progressively (rare)

Stationary:

The cam is a fixed to a frame, and multiple tooling with followers move around the cam. Most common on rotating machinery - such as a bottle labeling, capping, or filling machine.

The cam is a fixed to a frame and a tool with a follower slides along the the cam - e.g. a Slot Cam.

Follower-Profile shapes

The shape of the Follower-Profile influences the shape of the cam.

Roller shapes

Cylindrical Follower-Roller - commonly used

Barrel Follower-Roller (Crowned Followers) - commonly used

Logarithmic Follower-Roller - the actual logarithmic function is the intellectual property of each manufacturer.

Taper Follower-Rollers - occasionally used with barrel, globoidal cams

Other shapes

Flat-faced Follower - not as common as cylindrical

Knife-edged Follower - not a practical shape, but here for completeness

Other general shapes.

See Typical Cam-Profile Shapes

Follower Motion

The modes of Follower motion are:

Rotating Followers: a lever:

Swing back and forth:  an oscillating follower

Progressive motion, they index, in one direction

Translating Followers: a slider:

Sliding back and forth: a reciprocating follower

Stationary Followers:

A Stationary Follower moves the Cam. Not as common. Molding machines, wedge type cams.

Constraint between Cam-Profile and Follower-Profile

The constraint between the Cam-Profile and the Follower-Profiles influences whether the Cam-Profile is:

Force Closed:

The constraint is an external force

Gravity, Spring, Air-Cylinder, ...

Form Closed (also called Body Closed):

The constraint is another “body”:

Groove (Track), Rib, Slot, within which you constrain the Follower-Profile.

Conjugate Cams: these systems require manufacturing and production accuracy for two (or more) Follower-Profiles to be in contact with two or more Cam-Profiles.

Type of Motion

Non-progressive:

The follower returns to the same position after each cycle by reversing its direction of motion at some point in the cycle.

Progressive: (also called indexing motion, Indexing Cams

The follower moves progressively to a new position at the end of each cycle.

In most cases the follower is replaced by another follower at the end of a motion cycle. Equally spaced followers return to their original positions after a number of motion-cycle. Most indexing systems use several roller followers equally spaced around a follower wheel or 'turret'.