Teflon Disk In Place of a Slew Bearing 1

[Colfax]

I am using a steel plate resting on a teflon disk in place of a slew bearing. The material in contact with the teflon is steel. I know that the co-efficient of friction for teflon on steel is pretty low but is there any type of lubricant that would make it even lower? I have looked and looked but can't find the answers I need. Any help/guidance would be much appreciated!!

 

[MikeHalloran]

Most any kind of grease should help a bit.


Mike Halloran
Pembroke Pines, FL, USA

 

[IRstuff]

Just bear in mind that teflon will cold-flow under high compression, so if your load is heavy, you might wind up flattening the disk to the point of uselessness over time.

TTFN
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[MikeHalloran]

Also, make the steel plates more smooth and more flat.


Mike Halloran
Pembroke Pines, FL, USA

 

[dvd]

You might take a look at the recommended maximum PV (pressure & velocity) data for ptfe bearings contained on page numbers 4&5 of the following:

Bunting Bearings Catalog

There are thrust bearing pressure values listed.

Guidance with teflon is not possible like with a conventional slewing bearing. Once some eccentricity creeps in, the teflon can move where it wants. Hard to say whether teflon will perform without seeing some details about your application. Some sort of teflon flanged sleeve bearing might serve your purposes if the PV values concur.

 

[KENAT]

A. Are you sure PTFE is what you need per some above comments.

B. What Mike said about the finish of the steel - also bare steel may corrode over time (increasing friction) so what plating does it have (if any) as that will impact things.

C. Anecdotal information from an old colleague suggested that PTFE on UHMWPE was actually lower coefficient of friction than PTFE against PTFE.

D. If the answer to A is 'no' consider materials such as Turcite or PTFE impregnated acetal and similar.

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[3DDave]

Teflon is very soft and can abrade easily. It also can allow the mating part to embed. Even if the sliding friction is low, once dug in, the resistance to motion can go up.

HMWPE is probably better. It is a little higher friction, but it is much harder and won't displace and resists embedment.

The only application I've seen where teflon was chosen as a high load bearing material was replaced with greased bronze soon after.

No matter what, I expect the friction to be 10 to 100 times what a roller/ball bearing produces.

 

[MikeHalloran]

The P values given in the referenced Bunting catalog seem a little high to me.

For a particular carbon-filled TFE with which I have some experience, there was a 'sweet spot' at around 100 psi, above which the wear rate (at low speed) was excessive, and below which, in my particular special case, the leak rate between a stainless plate and plastic surface, both lapped to a couple of light bands, became excessive.

YMMV.


Mike Halloran
Pembroke Pines, FL, USA

 

[Colfax]

The metal plate was machined flat and as smooth as possible. The max pressure is only about 40 PSI. The velocity is negligible. The same design worked amazing in a previous project but the pressure was a little less than half of the current requirement. I'm just surprised in the drastic difference in performance from 20 PSI to 40 PSI. Maybe I am over looking something. Thanks for the help!

 

[KENAT]

"The metal plate was machined flat and as smooth as possible" well that's almost meaningless. Flat and smooth in my world would be less than .0002 flatness and perhaps 8RA microinches. This may be smoother or not smooth enough for your application.

However, as you've done similar before and it worked, I'd look again at suggestions of both surfaces being low friction material of some kind.

Have you tried googling, a quick search got me:

http://machinedesign.com/mechanical...ubrication-tips-plastic-gears-and-more-part-2

http://info.craftechind.com/blog/bi...s-for-Plastic-Bearings-Used-on-Metal-Surfaces

http://www.glt.ibg-monforts.com/en/ptfe-bearings-general-information.html

http://www.tss.trelleborg.com/remot...byscript/catalogs/turcite_b_slydway_gb_en.pdf

http://mtsandtg.com/system/ckeditor_assets/attachments/200/trel007_turcite_b_leaflet.pdf

(mentions specific lubricant at the end)

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(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[Colfax]

Thank you Kenat. Your links provided me with exactly what I needed. What i meant was with the tools available at our shop, the plate is as smooth as it is going to get.

 

[tygerdawg]

Or just buy a store-bought solution (assuming any of these would be a suitable replacement)

http://www.igus.com/wpck/3734/iglidur_prt

TygerDawg
Blue Technik LLC
Virtuoso Robotics Engineering

http://www.bluetechnik.com