Cam mate issues

Hi All,

I've got an assembly where a cam-mate enables a cylindrical follower
to run along a cam face.

Originally I had a solid brass bush follower running along it and the
model built and ran just fine. I've since upgraded to running a small
roller bearing follower in its place to reduce friction/stiction and I
can't get the cam follower mate to behave. The bearing is larger
diameter than the original solid follower by a factor of about 2.

It builds and give me the warning "some elements of the cam are of
smaller radius than the follower and this may result in instability"
or words to this effect. The mate previews just fine.

When I drag the cam however, the follower instantly flicks from
following the external profile of the cam to following the internal
profile. It's then stable and runs on this inner profile but that's
not what I need!

I've tried a number of things including making phantom faces, making
faces with all large radiuses (larger than the follower) etc and I
still get the same warning even though all radiuses should be large
enough to take the follower without instability. The same issue of
running on the internal faces persists.

Does anyone have any suggestions how to force it to run on the outside
only?

My next step will be to try fixing the follower (so that the bearing
doesn't rotate) and see if that makes any difference.... other than
that I'm out of suggestions.

Cheers,

George.

 

Well, the plot thickens.

Still no solution, so I went back to an earlier model, which worked
fine.

Now the original mate works fine, I can suppress it, unsuppress it and
it's robust. If I suppress the cam mate and add another EXACTLY THE
SAME, the new one has the exact same problem as with the new design.
Nothing has changed, one mate I made about 2-3 months ago and the
second mate I'm making today but they behave completely differently.
I'm runnning the same service pack as I was then, and it makes no
difference if I use a later or earlier service pack

 

FOUND THE PROBLEM!!!

Here's a tip guys, when doing cam follower mates, make sure the boss/
base extrude you use to form the cam face does nothing but form the
face. My cam had a couple of holes through the middle (think of a
hollow camshaft with lobes on the outer surface) and to be efficient
in the feature tree I'd extruded the holes as part of the original
base sketch. THIS WILL SCREW UP THE CAM FOLLOWER MATE. Once I'd
stripped those holes out of the original base and added them as
separate cut-extrudes elsewhere in the feature tree, it started
behaving itself! Fingers crossed this'll come up in a search if anyone
has a similar problem in the future.