Cam-Follower Design Arrangements

This topic reviews the different ways it is possible to support the cam-follower roller in the cam-follower arm.


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

hmtoggle_folder1        Stud-type and Track-type Cam-Followers

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

Stud-type Cam-Follower
Track-Follower Cam-Follower

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

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

tog_minus        Stud 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.

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


tog_minus        Track Cam-Follower

Cam-Follower-Yoke-20181122

Yoke Support

The cam-followers use a 'yoke' arrangement to support the cam-follower. It is also called a 'clevis' support.

In the image:

The left-side of the support pin/shaft is in contact with the 'inner-ring'.
When the nut is tightened, the shaft is pulled against the left-side of the inner-ring which forces its right-side against the inside face of the yoke.

Thus, the inside faces of the 'yoke' do not deflect inwards when the nut becomes tight.

The outer-ring is allowed to float axially. However, if it experiences axial thrust, it moves against the inside face of one of the two flange rings [in black].

Cam-Follower-Yoke2

It is possible to use two 'circlips' (snap-rings) to locate the pin/shaft.
The inner-ring might move to the left or right, up against the yoke.
The outer-ring floats to the left or right, up against the flange-rings.

See Specification of Stud and Yoke Cam-Followers for more information.

hmtoggle_folder1        Stud Cam-Followers and Form-Closed Cams

tog_minus        One Stud Shaft - Groove 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 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 Cam-Follower 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 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 rubber. The rubber roller can be loaded against the cam track to spring the rigid roller against the other flank of the track-cam. Also applies to Conjugate and Rib cams.

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_minus        Two Stud Shafts - Conjugate-Cams

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

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

Conjugate Cams

The Cam-Followers are not on the same shaft.

Each cam-follower has a loading at different timing points in the machine cycle. The net force against each cam-follower is often different.

The placement of the cam-follower bearing in the follower arm can be optimised to suit the particular loading cycle it experiences.

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