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miner00 (Mechanical)
19 Jul 02 12:47
I have always heard that it is a bad idea to lubricate plastic gears because residue from normal wear will mix with the lubricant to create an abrasive paste which adds to the wear problem.  Is this true?  Has anyone had experience with this situation?

My application is with a set of 1" gears made of Nylon 6/6 with 30% carbon Fiber and 15% PTFE.

Thanks
Guest (Visitor)
19 Jul 02 17:16
plastic gears are normally not lubricated.
miner00 (Mechanical)
19 Jul 02 18:32
I'm sorry for the confusion. To clarify my problem:

I have a system with a plastic gear train, as described, that has run about 350,000 cycles and the loading is such that the gears have worn through abrasive wear to the point of failure.  I am looking to see if lubrication is even an option in this scenario.

I realize that plastic gears are normally considered self lubricating, but in this case the lubricity within the plastic/design is not sufficient to meet the needs of this part.
GregLocock (Automotive)
21 Jul 02 20:12
I've never done this, but could you teflon coat them? I think there are some fairly user friendly processes now, although you may still need a metal substrate.

Alternatively - graphite powder.

Cheers

Greg Locock

CoryPad (Materials)
21 Jul 02 21:43
fluorocarbons like Teflon are compounded into polymers (frequently for gear applications), not coated onto them.  I have no experience with separately applied lubricant.
Helpful Member!  Biggadike (Mechanical)
22 Jul 02 2:58
We regularly find we have to lubricate plastic gears.
You can try Molycote PG75 which is a silicon based grease designed for just that purpose. Normal greases cause problems on plastic parts.
cgrace12 (Mechanical)
22 Jul 02 9:12
We found white lithium grease to be useful... but you will want to test it, it may compound the problem.  Are the gears wearing at the teeth or the bearing?

Chris Grace
Product Development Engineer
Sterilite Corp.

Helpful Member!(2)  TVP (Materials)
22 Jul 02 12:01
Lubricants are frequently used for plastic gears, either as part of the plastic compound, or as a separately applied substance.  Silicone-based lubricants are generally used in addition to PTFE for aggressive applications.  You may need to consider the entire package (base resin, reinforcement, lubricant, etc.) if the wear is this significant.  LNP has some good resources on-line regarding thermoplastic gears, lubricants, etc.  The website is http://www.lnp.com/LNPSite.nsf .
TVP (Materials)
22 Jul 02 12:03
I forgot to mention that the publication is called A Guide to Plastic Gearing and can be accessed by clicking on Publications then Brochures and Bulletins and then the .pdf file.
plasgears (Mechanical)
16 Dec 02 11:22
All the plastic suppliers recommend prelube of plastic gears even if there is no further lubrication. I have dumped plastic gears into a bath of synthetic oil, then centrifuged the batch and stored the lot in plastic bags. It will aid run-in and increase life.

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