Cam-Follower Design Arrangements

When a bearing in contact with the cam is circular, we give it the term Cam-Roller. The Cam-Follower is the Part that supports the Cam-Roller Bearing.

Stud-type and Track-type Cam-Followers

Generically, there are two types of cam-roller bearings:

Stud
Track

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 - axial guidance, type of lubrication, sealing, corrosion, et.c. .

tog_minusStud-type Cam-Follower

Typical Stud Cam-Follower on Cam

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

Stud Type Cam-Rollers

Most typically:

the stud is also the Cam-Roller bearing's inner-ring.
the nut pulls the side plate of the bearing against (a flange on the) cam-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 fine adjustments of the roller axis. This adjustment is often used to eliminate/reduce backlash between the cam-roller and the conjugate cams/

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


tog_minusTrack-type Cam-Follower

Cam-Follower-Yoke-20181122

Track Type Cam-Rollers

A Yoke (clevis, fork) and Pin supports the Cam-Roller.

In the image - the important detail to note is:

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 move axially, without restriction, 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 Cam-Roller

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

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.

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 Cam-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-rollers that do need to change their rotational directions (see DESIGN 1)

 

DESIGN 2A:

Two Cam-Rollers - Equal Radius

See image 'DESIGN 2A'.

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

There are four surfaces to machine: two working/active surfaces for the cam-rollers to roll against, and two non-working/clearance surfaces to make sure the Cam-Rollers do make contact.

 

DESIGN 2B:

Two Cam-Rollers - Different 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

These 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.

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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