Can nylon gall aluminum
Can nylon gall aluminum
(OP)
I am working an a design that involves a linear sliding interface. One of the surfaces is 6061-T6 and the other is MDS filled nylon.
I chose MDS filled nylon because I heard it was good for bearing surfaces. It turns out that the aluminum surface, which initially was smooth (~32), now looks like what can best be described as a galled surface.
Is it possible for nylon to gall aluminum? What materials would be better than MDS filled nylon? I can not use any lubrication nor can I use Teflon.
Thanks,
Kevin
I chose MDS filled nylon because I heard it was good for bearing surfaces. It turns out that the aluminum surface, which initially was smooth (~32), now looks like what can best be described as a galled surface.
Is it possible for nylon to gall aluminum? What materials would be better than MDS filled nylon? I can not use any lubrication nor can I use Teflon.
Thanks,
Kevin





RE: Can nylon gall aluminum
UHMWPE or maybe Delrin or some other acetyls like Pomalux might be worth a look depending on application.
KENAT,
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RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
I was going to try both Delrin and UHMW. I think we have some laying around here. I'm not familiar with Pomalux.
RE: Can nylon gall aluminum
I suppose it's possible. I bought it from Mcmaster. They have made mistakes before.
RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
Look at what Igus is doing, they've got great information on their bearing materials and wear characteristics with different shafting materials.
James Spisich
Design Engineer, CSWP
RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
KENAT,
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What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Can nylon gall aluminum
Kenet - We have not ruled out contamination. After the first test there were aluminum particles as well as a few very small machining type chips laying around. The orientation is such that any particles shed fall away from the test surface. I know this may be hard to imagine without a picture. The test surface is near the upper most portion of the machine.
Thanks for the ideas so far.
RE: Can nylon gall aluminum
TTFN
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RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
TTFN
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RE: Can nylon gall aluminum
The best plastic to use as a bearing is very dependent on a number of factors, including the nature of the opposite surface, lubrication, cooling, speed, pressure and cycle rate.
Hard anodizing the aluminium would help a lot. Even a bit of water as a lube can help. unmodified nylon might do better. Are you sure your nylon is not glass fibre reinforced. The presence of glass fibres certainly gauls aluminuim. I have never seen molly and graphite filled nylon gaul aluminium in the past, but I have only ever used it in contact with aluminium in piston buttons to hold gudgeon pins in place where the circlips are prone to fail. This is hot, bathed in oil and has little motion against the aluminium surface. I suspect glass fibre is present in the nylon.
Regards
Pat
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RE: Can nylon gall aluminum
MoS2+ graphite + aluminum = battery.
The MoS2 acts as an electrolyte and the aluminum corrodes.
RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
Bar stock is unlikely to be nucleated. Fast cycle injection moulding grades are nucleated, but may be difficult to get in the size and numbers you require but it's no big deal if you can't get it unless the nylon part fails.
Nylon 4.6 or Stanyl is a better bearing than type 6 or 6.6 and is inherently crystalline enough to not need extra neucleation, but is a lot more expensive and not justified unless you have a failure with the others.
Regards
Pat
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RE: Can nylon gall aluminum
Cheers
Greg Locock
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RE: Can nylon gall aluminum
Is there any reason you don't want a bearing grade of teflon?
UHMW as many have said is a good solution. It can be found in tape form for a quick test. It could also test the galvanic corrosion theory.
Hard anodized AL parts can also be treated to reduce friction.
RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
Some quick replies.
Teflon is ruled out because it is considered a contaminate in one of the environments we will operate.
That IGUS tool is awesome.
It is quite possible our loading PV is too high. I will follow up with that.
We must use aluminum because of weight. Hard anodizing while not optimal for us is not out of the question.
I'm not sure if the material I used contains graphite. The only description given was 'MDS filled cast nylon 6'.
MinyJulep - You mentioned corrosion caused by the combination of materials. Would this be a factor in just a couple of hours?
RE: Can nylon gall aluminum
You've got all the parts - do a test.
RE: Can nylon gall aluminum
RE: Can nylon gall aluminum
MDS filled Nylon would never even be on my list, neither would 6061 in a T6 only condition.
Use UHMW and anodize....
Charlie
www.facsco.com
RE: Can nylon gall aluminum
"Teflon is ruled out because it is considered a contaminate in one of the environments we will operate."
Wow! That's a weird operating environment. One of the most desirable properties of PTFE is that it is the single most chemically inert and stable substance known to mankind.
As for filled nylon galling aluminum, that's what you would expect if debris is present in the contact area. The bits of debris embed themselves into the softer nylon surface and then abrade away the relatively harder aluminum mating surface. The aluminum surface exhibits the wear patterns since that is the joint component that is sliding relative to the debris particles. The nylon does not exhibit wear patterns since the debris particles are easily embedded into its soft surface.
You need to find the source of the debris. Nylon is corrosion resistant and chemically stable, so I doubt it's the source. Aluminum on the other hand, oxidizes very readily, and aluminum oxide is a very hard and abrasive compound.
Good luck.
Terry
RE: Can nylon gall aluminum