Re: less friction: delrin on delrin or delrin on steel?



Steel? Did I win? Delrin on delrin will wipe together-too smooth. Polished steel works better.
Did I win?
wws
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Alex wrote:

The delrin and metal combination would have less friction.
Rick
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Another option is Teflon against aluminum extrusion. Would it have less friction than Delrin against polished stainless?
Thanks

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Not sure I'd know the answer to that one, Alex, but I can't imagine that aluminum would be lower in friction unless you used a very hard alloy, perhaps something like 7075-T6, or you anodized the parts first. Seems to me the softer aluminum alloys would have a relatively high wear factor.
Harold
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to
We always anodoze the aluminum member.
The glides are of UHMW, in a box extrusion appx 4in x 4in square, up to 24 ft long with an open side for mechanical connection to the load. The carriage is internal, belt driven and 10in long, with 4 glides at each end--total glide surface contact is ~appx 8" sq.
The servo is 10 amp and max velocity is ~ 2ft/sec (estimate) ---Average mass loading on the motion plane is ~ 20lbs likely( again estimated ).
Units have been tested in the lab to simulate over 8 yrs of usage and no failures have occured.
I cannot divulge actual customer product or give more than general info as to design details without breaching confidentiality agreement as this is my customer's product and design engineering.
==========There are available "channell" style uhmw extrusion as well as pre-made round bushings designed just for this function--And they are quite inexpensive.
In retrospect, I would suggest anyone designing linear slides using plastic bearings should investigate by consulting with the plastics suppliers, likely they will have much data on hand as to proper selection and engineering so that the proper choice can be made based on intended function of the completed unit.
HTH
--

SVL








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Can't cha' take a flat piece of delrin, steel, or SST and place a piece of delrin on it with a bit of weight and raise one end to see which has the lowest angle before sliding?
Makes sense to me...!
Regards,
Stan-

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Alex,
Delrin on SST, if it's polished.
If you need plastic on plastic, Valox has a lower coefficient on itself than just about anything. It's very "delrin like" machinig wise, and very similar mechanical properties. It is a bit more expensive though.
Regards
Mark

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Alex,
There are a lot of smart folks on this group (me not necessarily being one of them) and if you give us a bigger picture of exactly what it is you're working on (unless it's a top secret not yet patented idea), it might help.
Bob
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No one yet mentioned cleanliness. I see a ton of failures of various Steel materials on various plastic materials materials due to dirty shops and poor practice in cleaning before assembly. Had one (actually many similar) occurrence where the installer did a bunch of grinding on stainless piping above a machine and then reassembled the parts of the machine without cleaning. The grinding dust seated into the plastic and made a really nice honing stone for the expensive stainless steel chain.
Also....just because you go for the lowest friction by the "book" doesn't always translate to real life. I constantly have engineers telling me that the book says that large roller double pitch roller chain has a friction of .1 whereas chain sliding on a plastic runner is higher. They always forget that in practice (these applications) the chain rollers eventually lock up and are dragging steel on steel.
The moral is, there's more to the story than just friction factor. Remember the realities of use too.
Koz
Alex wrote:

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