OT - Plain Bearing Material Problems

I have designed a small rotating assembly that runs at only 0 - 150 RPM with
very very minimal load, it has a Stainless Steel (303) 3.0mm Dia shaft and a
brass (CZ121) bearing. When first assembled this it has a very smooth
running action and very little stiction, but after a few days of use the
bearings begin to squeek and seize.
Can anyone tell me if there any problems with stainless and brass as a
bearing assembly or point me in the right direction for information on
suitable material pairs for bearings.

Simon

--
SGM Design Limited
Prittlewell House
30 East Street
Southend-on-Sea
Essex
UK
Tel: 0044 (0)1702 601607
Fax: 0044 (0)1702 602607
E-mail: -move-me.co.uk

 

You may get a good answer from this group, but I'd urge you to post also
in "sci.materials" and "sci.engr.metallurgy". You're almost certain to
get some very expert opinions there.

Mark 'Sporky' Stapleton
Charlotte, North Carolina, USA

 

Simon,

If the assembly needs to run un-lubricated and with low stiction,
you may want to consider a plastic bearing (eg Teflon, or one of
the bearing grades of Nylon). Look at printers / photocopiers
around the office for typical exaples. If heat and / or load are
too high for a plain plastic bearing then look at commercially-
available sleeve bearings (bushes) such as Permaglide, which are
available with a Teflon-impregnated sintered surface.


Rick.

 

Ditto, totally agree. And/or suggest using rulon, peek, torlon, uhmw pe
or delrin, depending on the conditions, as well.

...

 

You might find something in the IGUS line that would be suitable.

http://www.igus.de/Default.asp?LANGUAGE=E


Art W.

 

While I am no expert, we have also used Nylatron in similar situations.

This is probably overkill for your low load, low speed application. I
suspect some UHMW would work pretty well.

 

I have prototyped both Oilon (oil impregnated Nylon) and delrin bearings.
The problem I found was due to the fact that the assembly was so small, the
machining proved difficult, the burr left behind effected the rolling
resistance or the required break edge affected the end float beyond limits.
I require an external running surface of stainless and cannot have a fully
plastic wheel. That has brought a thought that maybe I could run with a
Plastic shaft!!!
This assembly is to be used in the clothing manufacture industry and
therefore quite a dusty and dirty environment, this has lead me away from
lubricants!

Simon

 

Sounds like a S/S wheel/roller with a Permaglide bush running on a
S/S or hard chrome shaft might be the answer. If possible, protect the
bush against ingress of lint, dirt etc.

Another thought is to use a shielded ball-bearing race in the roller - NSK,
for example, have shielded metric-series miniature bearings in 3mm bore
(MR63ZZ, 683ZZS ...) which might also be a viable solution.

Rick.

 

Simon,
Check out someone like IGUS (http://www.igus-uk.co.uk/) or Railko
(http://www.railko.co.uk/index.html)

Cheers,

Kev

 

Yeh, I was not necessarily thinking of oil impreg bearings or them being
machined,.. more towards something w/o oil impreg or injection molded
bearings (but can also machine,.. your burr problem sounds like a
machining/quality issue).

Without fully understanding the design I think we are giving you any
suggestion we can so...

Knowing it will be in a lint environment, where a dry bearing is
preferred, and as someone noted, using wipers and sealing areas are
worth it.
Someone also mentioned ground or hardened sstl shafts, that should be
used.
Now, you're considering a polymer shaft? (electro static conditions may
arise attracting more lint) Hmm... some of the high glass filled shafts
are probably the only ones I can imagine for torsional use.. 3mm dia
extrusion possible... ?

...

 

My first port of call was the ball bearing (OD6 x ID3 x W2). It failed on
two counts really, the stiction was quite high, which surprised me and the
noise level was unacceptable. The device that these roller assemblies fit
into is a hand held injection moulded case and seemed to amplify the bearing
noise, hence the change to plain bearings.

--
SGM Design Limited
Prittlewell House
30 East Street
Southend-on-Sea
Essex
UK
Tel: 0044 (0)1702 601607
Fax: 0044 (0)1702 602607
E-mail: -move-me.co.uk

 

SKF has a plain composite bushing/bearing ....stainless steel backing with
ptfe coating inside...not sure about if they are avaliable in such small
dimensions though

Krister L