Recommend plastic for strong wear resistant

[petersi]

HI,

I'm looking for plastic that can be last longer in my application. It is a transmission joint. It has 2 parts, the cup and the axle. I want to make the cup as light as possible, so plastic is my first option. Derlin works in this application but I want something that last longer. Want to know what kind of plastic is better in this application.

Pictures means thousand words, so I drew the parts. Please check the attachments. The fist picture is showing the parts are new.The second attachment shows the wear out area after the parts has been used. Thanks

 

[patprimmer]

If Delrin works, what specifically are you looking to improve.

Acetal homopolymer such as DuPonts Delrin is a very hard wear resistant plastic in it's natural state. It is poor to UV light and not good at elevated temperatures. I can only take a completely unsubstantiated guess if these are qualities that limit its effectiveness in your application.

Additives can improve it. Other plastics can be better at high temperature.

Ultimately wear resistance depends on a number of factors and many plastics have their strengths and weaknesses.

Regards
Pat
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[MikeHalloran]

The line contact between the cross pin's cylindrical OD and the cup slot's flat surface has, theoretically, zero area, and therefore produces very high stress under torque. In practice, the cup slots wear until the contact area is finite and the contact pressure goes below some threshold value.
The joint will probably last longer if there is some angularity between the cup's axis and the shaft axis, especially if some lubricant is present.

Substantially longer life could be had by sleeving each of the cross pins with a bushing having a square or rectangular 'OD' and a cylindrical bore, so that the contact area between the flat faces of the bushing exterior and the cup slot face is finite to begin with. The bushing would need a flange adjacent the proximal end of the cross-pin in order to retain it in place.





Mike Halloran
Pembroke Pines, FL, USA

 

[petersi]

Thanks for much for the reply. Delrin works like about 3 days in our application. There is no high temperature for this machine.

MikeHalloran, you must mean something like this, the clip. It install on the axle pin. Please check the attachment. We have tried this method. It makes the cup last a lot longer. All the wear goes to the clip's hole. The clip last like only 3 days too.

What do you suggest the material use on the clip?

 

[MikeHalloran]

I'm a little fuzzy on how the clip fits into the assembly.

But if it has finite wear areas and still doesn't meet your life requirements, your solution space may not include plastics of any kind.

Similar joints are used in model boats and model locomotives, but the loads are pretty low, and the typical material is nickel plated brass.



Mike Halloran
Pembroke Pines, FL, USA