Need high fatigue life alternative to ABS
Need high fatigue life alternative to ABS
(OP)
Hello,
I am looking for recommendations for an alternative to our current ABS material that is failing due to fatigue.
Our current part is failing in the field after 3-6 months of use. The failure is a fatigue failure near the pivot pin of a trigger. The surface shows typical clamshell patern failure and it is slightly polished where the break starts and whit/grey where it the break ends.
We used a PC/ABS blend on a prior version of the part and by going to the ABS (Entec-Resins 756) almost doubled the life using our stress test jig.
Shrink rate may not be totally critical so I am open to going away from ABS altogether.
What are my options?
Glass filled ABS
mineral filled Nylon
PP
Thanks!
I am looking for recommendations for an alternative to our current ABS material that is failing due to fatigue.
Our current part is failing in the field after 3-6 months of use. The failure is a fatigue failure near the pivot pin of a trigger. The surface shows typical clamshell patern failure and it is slightly polished where the break starts and whit/grey where it the break ends.
We used a PC/ABS blend on a prior version of the part and by going to the ABS (Entec-Resins 756) almost doubled the life using our stress test jig.
Shrink rate may not be totally critical so I am open to going away from ABS altogether.
What are my options?
Glass filled ABS
mineral filled Nylon
PP
Thanks!






RE: Need high fatigue life alternative to ABS
RE: Need high fatigue life alternative to ABS
ABS and PC are probably the worst choice possible for a bearing of any sort...
As dwightdixon has suggested, Acetal would be the best choice - moulded correctly (i.e. high tool temperature) it will give good fatigue performance. It is the only polymer used as a 'spring'.
You might look at filled versions (probably mineral to reduce warpage), to get the shrinkage value down as it is quite high as an unfilled material compared to ABS. (Although it may only require a core pin change from your op).
Cheers & beers
Harry
RE: Need high fatigue life alternative to ABS
Looking back the breakage was more from impact, and if you hit anything hard enough I suppose you can break it. The fatigue failures I am seeing now are driving me crazy.
The choices in filled material are endless, what will a mineral filled acetel's impact strenght be (comparable to the current ABS is fine)
Thanks again!
RE: Need high fatigue life alternative to ABS
There is not any memory with less satisfaction than the memory of some temptation we resisted.
- James Branch Cabell
RE: Need high fatigue life alternative to ABS
Impact modified Acetal/POM is readily available.
Harry
RE: Need high fatigue life alternative to ABS
You give no indication of the application nor the environment.
Nylons are very good to fatigue as are acetals, polyesters, polyolefins and polyurethane.
Acetal is chosen over nylon for springs because of it's better and more consistent flex mod and it's somewhat better creep resistance.
Polypropylene is used in live hinge applications that need to go through millions of flex cycles in applications like automotive throttle pedals.
Nylon is used in mechanical components and housings for power tools like jig saws, vibro sanders and hammer drills.
Large concentric radii vs sharp transitions will at critical junctions of parts will dramatically improve the fatigue life of any plastic part.
Regards
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RE: Need high fatigue life alternative to ABS
Nylons and polyesters respond particularly well to fibre glass reinforcement.
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