best mat'l for impact resistant washer

[pparent]

I have an application where I need to make a custom plastic washer (10000 units) that would resist repetitive impact from a solenoid shaft shoulder for 2M cycles +. The temp of operation is -25 deg C to +70 deg. C

1/32 thick, 1" dia. Right now, a basic Delrin washer is colapsing and then cracking prematurely (500 000 cycles).


I was looking for UHMW, Nylatron, Polycarbonate? or other sugestions?

thanks

pp

 

[patprimmer]

Glass filled nylon 6.6 (possibly also impact modified to avoid splitting at -25 deg C) or polyurethane, depending on hardness required

UHMWPE will be more prone to pounding out than the Acetal was.

PC has poor fatigue resistance and poor resistance to many common solvents.



Regards

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[pparent]

Thanks patprimmer,



has anybody had experiance with Hydlar (kevlar reinforced nylon). This stuff should be able to withstand impact and shocks? I think polyurethane would be too soft...

 

[patprimmer]

I don't think Aramid fibre reinforcement will suit your purpose any better than glass fibre. Long glass will do better, but will be more sensitive to flow direction as the longer fibres line up better with flow direction.

Regards

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Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[Pud]

Hi,

Many years ago we made washers which were used to buffer the air driven slider in a pneumatic road drill (jackhammer in US?) along with handle isolation mounts.

They were made of a polyester elastomer - hard grade - made by DuPont called Hytrel (there are others, such as Arnitel, by DSM, etc)

The reliability engineers at the company were amazed how it outlasted the polyurethane they were currently using. In excess of 5m cycles if I recall correctly - certainly into 6 figures. The material in the harder grades is also very 'dead' and is used in vibration absorbing applications as well, making things quieter.

If you contact the material manufacturers you might get a sample big enough to punch yourself a sample washer out to try.

Rgds

Harry