Cam-Follower Design Arrangements

Note: See Cam Follower Roller: Design Specifications to review the technical requirements of a Cam-Follower.

Stud-type and Track-type Cam-Followers

Generically, there are two types of cam-follower bearing types:

Stud-type
Track Followers

SKF cut-away views of Stud and Track type Cam-Followers

Both the Stud and Track types have many variants to suit different applications and working environments.

tog_minusStud-type Cam-Follower

Typical Stud Cam-Follower on Cam

Stud Cam-Follower. The Stud is also the inner-race to the bearing.

Cantilevered Support

Most typically:

the stud becomes the bearing's inner-ring.
the tightening nut pulls the side plate against (a flange on the) follower.
they have one or two sets of rollers or balls.
they may have shields, seals, or neither.
they may have an eccentric sleeve to make possible fine adjustments of the roller axis. This is used to eliminate backlash between the cam and the conjugate rollers, or to make

The Cam is typically 2-3mm wider than the Cam-Follower to prevent 'edge' stresses.


tog_minusTrack-type Cam-Follower

Cam-Follower-Yoke-20181122

Note: A Track-Type Cam Follower cannot usually be used with a Track-Cam [Groove-cam]


Yoke Support

A 'yoke' [clevis, fork] arrangement supports the cam-follower. The fork supports the cam-follower on both sides.

In the image - the important detail to note is:

The left of the support pin/shaft is in contact with the 'inner-ring'.
When the nut tightens [on the right], the shoulder of the support 'bolt' [on the left] moves to the right and is forced against the left side of the bearing's inner-ring. This pulls the inner-ring up against the inside face of the right-hand fork of the yoke.

Thus, the forks of the yoke do not deflect inwards when the nut becomes tight.

The outer-ring can float axially by approximately 0.2mm.

Cam-Follower-Yoke2

It is possible to use two 'circlips' (snap-rings) to locate the support pin.
The inner-ring might move to the left or right, up against the inside faces of the forks and yoke.
The outer-ring floats to the left or right, up against the flange-rings of the track bearing, and not the yoke.
The outer-ring should not touch the inside of the yoke.

See also: Specification of Stud and Yoke Cam-Followers .

Stud Cam-Followers and Form-Closed Cams

tog_minusGroove or Track Cams

Typical Cam-Follower, with Stud, in a Cam-track.

DESIGN 1: Typical Cam-Follower, with Stud, in a Cam-track.

DESIGN 1:

One bearing Roller

To allow the roller to rotate, the width of the cam-track is greater than the diameter of the cam-follower.

Thus, the design has two disadvantages:

1.Backlash:

The clearance between the cam-follower and the cam-track, like any other backlash in the system, will cause impact forces (knocking) when the backlash is traversed.

2.Wear:

When the cam-follower moves from one side of the cam-track to the other, the roller must rotate in the opposite direction. It cannot change its rolling direction instantly. Thus, it skids (slides) until it rolls along the cam surface again. The skidding action wears the roller and the cam surface. Also called scuffing wear.

Two, equal diameter Stud Cam-Follower. The cam faces must be relieved opposite

DESIGN 2A: Two, EQUAL diameter Stud Cam-Followers. The 'deeper' cam-track must be undercut.

DESIGN 2:

Two bearing Rollers

There are two bearings on the same stud / shaft. These designs aim to:

1. Reduce Backlash

With good manufacturing tolerances, the backlash can be reduced.

2.Reduce Wear

The rollers do not need to change their rotational directions, and thus they do not scuff/wear as much as those cam-follower that do need to change their rotational directions.

 

DESIGN 2A:

Two bearing Rollers - Equal Roller Radius

See image 'DESIGN 2A'.

When the roller diameters are equal, each roller must have a clearance for it non-working flank.

The cam-profile for the 'deepest' roller must be 'undercut'

 

DESIGN 2B:

Two Rollers - Different Roller Radius

See image 'DESIGN 2B'

The cam-profile does not need to be undercut. It is easier to manufacture.


Note: When the load is small, and the rotation speed is low, and the elimination of backlash is important, one roller can be steel and the other rubber. The rubber roller can be loaded against the cam track to act as a spring to force the rigid roller against the other flank of the track-cam, to act as a 'pre-load'  Also applies to Conjugate and Rib cams.  The pre-load force might be quite low. Example: Camera Lens.

Two, DIFFERENT diameter Stud Cam-Follower. The deeper cam-track does not need to be undercut.

DESIGN 2B: Two, DIAMETER diameter Stud Cam-Follower. The deeper cam-track does not need to be undercut

tog_minusConjugate-Cams

Typical Cam-Follower, with Stud, in a Cam-track.

DESIGN 1: Typical Cam-Follower, with Stud, in a Cam-track.

Conjugate Cams have two bearing / rollers, which are not on the same shaft/stud.

Each cam-follower is at a different position in the cam-follower. The net force against each cam-follower is often different.

The advantages:

The diameter of the cam-follower bearing can be different to suit the particular loading cycle.

For example, the lower roller supports the weight of the gravity  loading and top roller does not.

With accurate machining, backlash can be eliminated, are a pre-load applied between the bearings.

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