Pin in Cam Profile

[solocam92]

I am currently running a metal dowel pin in a milled out cam profile shaped similar a tear/water drop. The material that the profile is milled into is a sort of hard plastic but I am seeing extreme wear (abrasive) at the top of the profile where the pin has to switch direction. Does anyone have a suggestion for a lightweight material that would wear less than the plastic when coupled with a metal dowel pin?

 

[tbuelna]

Don't make the mistake of addressing the symptom rather than the cause. The first thing you should do is perform a kinematic analysis of your cam and follower system. Once you have determined the forces, sliding velocity, and contact pressure at the cam/pin interface throughout a cycle, you can make a more informed decision on what corrective action to take. The best approach might be to modify the pin diameter and/or the cam profile. Or it might involve using a different material for the cam.

If I were to venture a guess of what is causing your problem based simply on the limited information provided in the OP, I'd say your cam profile and pin diameter are creating a very high pressure angle at this particular point. And the high pressure angle is producing excessive contact stress on the plastic cam surface.

 

[Tmoose]

got some pictures of the worn cams? And the pin?

 

[solocam92]

Here is a picture of the cam profile. On the left side channel you can see the wear. The pin is a standard 0.5 inch metal dowel pin.

 

[tbuelna]

Cripes! I can see wear everywhere on that part.

Can you provide a sketch of the mechanism's geometry? Is the follower mounted on a rocker arm or does it just translate? How is the follower positioned and how is it constrained relative to the radial cam surfaces? Is there any form of compliance or elasticity in the mechanism, such as a preload or return spring?