Epoxy matrix bearing material DIY

[PekkaNF]

I have been considering trying epoxy filled with materials to make plain bearings.

Latest inspiration came from this thread:
http://www.cnczone.com/forums/epoxy-granite/126563-epoxy-bearing-material-method.html
Attached a link to a powerpoint presentation:
Bearing - CNCZ.ppt

3 parts Bronze powder
2 parts Aluminum powder
8 parts Molybdenum disulfide powder
3 parts Teflon powder
3 parts Calcium carbonate powder
1 part Graphite powder
Sufficient epoxy to make a paste with the consistency of soft butter

I pretty much all other materials, but have problem with two incredients.

First is teflon. Most DIY bearing composites seem to contain teflon, probably counting keying it mechanically on matrix instead of bonding?

Don't really get the use here, it is very difficult to bond. Proper teflon powder with epoxy wetting coating is hard to get. I'm considering other plastics. POM plastic granulate is easier to get, but particle size is closer to 2 mm....metal powders I have are around 60 microns.

Another part is calsioum carbonate. I know that it is normal filler for epoxy composites. But I am having hard time understanding use and idea behind it. If it is pure calsite it's hardness is about #3 mohs - i.e. about the same than copper, but lime stone too is calsium carbonate and it sounds abrassive. Also to get kilo of that is not trivial. As a nutrient suplement it costs about 18€/100g, other forms are not that pure and as a epoxy filler grade I sould buy 50 kg of it...

Ideas?

Pekka

[John Rudd]

Calcium carbonate = chalk....
Local school supplies?

[naffsharpe (Nathan)]

To me it looks like the recipe is an attempt to produce an epoxy version of a sintered bearing material. Instead of having the porous nature of sintered materials it is using the CACO3 as a "sponge " to absorb and later release oil/lube.
This idea would only work with the exposed CACO3 so I may be, and quite possibly am , totally wrong-----again!
Nathan.

[PekkaNF]

Nathan you may be onto something here....Pretty much all of the fillers will be eposed at the bearing surface. Clearly the idea here is work under lubrication too. Then I wonder the role of the teflon even more.

Didn't come to think that...I was onl thinking of dry operation and transfer of graphite/teflon onto sliding  surface. Dry operation....I could drop the calsium carbonate out or substitute with some bulk type filler?

Pekka

[naffsharpe (Nathan)]

I think that the Teflon/PTFE should be omitted for a dry bearing at high speeds , (it releases, I think, Hydrogen Cyanide under pressure/heat),and increase both the Moly and Graphite. This then allows the metallic materials to be lubricated in a dry form. That then begs the question, why use a filler (CACO3) , if no external lube is to be used?
If we then use,  at some time, a water soluble cutting fluid , then the Moly will float on a Graphite slurry because the Moly will reject the H2O but the Graphite will accept it ?
Again, I could be and possibly am, wrong !
Am I digging a hole for myself? To be interred by a more knowledgeable member is not the way I want to go!!
Nathan.

[PekkaNF]

Thank you. You really gave me something to look into.

You clearly know whole lot more about this topic than I do. Please keep on posting!

I do think that these coctails are developped do "do it all" orginally. And probably some incredients are added because they sound the part. One mix has to work with oil and without, maybe that is why both types of fillers are mixed.

I have some experience on teflon and such traditional bearing materials. It is used at the work, but not in parts that are analogous or usable to me. I can ask engineers some questions and they normally have answers. But some very spesific industrial producs are pretty far from my hobby projects. I have made some bearings from teflon bars. Not really loving that material.

Now I'm wondering if it would be easier to formulate separate mixes to different uses?

I have need for two different uses: a) dry (oilless) slow movement and low pressure (low load vs. surface area). b) other is not immediate, but I have one lathe that needs "moglice" but it is that crappy that it will be more for the love of the art than worth a lot of investment. lathe slides are traditionally lubricated and very little need for "emergency" lubrication qualities...however they should not stick hard and speed is most often very slow.


Suggestion for dry bearing mixes?

On all bearing mixes epoxy should as little as possible, plastics fillers and epoxy will limit working temperature range (that is not really problem for my immediate uses).

Very different spesific gravity or active incredient particle size is somewhat problematic..we don't want strong separation or orientation when mixed and applied. Classic is to get microballons to "float" on resin ritch mixture when worked too had.

Pekka

[chipenter]

PTFE has good friction and were propities and can be had in liquid form for plumbers .

[naffsharpe (Nathan)]

Pekka, thanks for the compliment but I have to say that it's undeserved! I'm far from being an expert in these things. My comments are just "thinking aloud" and are based on my own experiences with mechanical seals using dissimilar materials.
As Chipenter points out, PTFE/Teflon is a great bearing material, my worry is as yours, that maintaining the bond of small particles is very difficult.
I think that even if you could get a good bond at "powder" size particle, machining would reduce the bond and could lead to tearing the particle out of the matrix. A larger particle size would be better for machining as the bond is over a larger surface area.
Staying on the particle size of the components in the bearing, why not go with larger Carbon instead of Graphite powder? I'm thinking along the lines of smashed Carbon brushes/Pencil lead. Even to the extent of using Bronze/Brass/Alu/Iron swarf. It would need to be machined (for the bore) in small increments of drill bit size before boring on the lathe but would give more bearing materials exposed with less destruction of bond?
An alternative springs to mind, have you considered (for a dry bearing) using gland packing? It's available both PTFE and Graphite loaded. An accurate cylinder allowing for the thickness/section of the packing and the shaft diameter, fixed at one end and with an internal thread and mating plug may
 just do ?
Nathan

[PekkaNF]

Thank you Nathan, that is one way to go and I did follow it and almost bought a meter of packing cord.

However my most immeediate interest is sort of "flat" bearing on guideway/slide.

But good news is that I am fong to get some teflon granule and teflon/carbon granule to test.

Now this leaves me to find calsium carbonate that does not contain abrassive particles on that size that might become a problem.

I understand a little of seal problems, I have heard some rubber seals that pure carbon filler was substituted with fly ash from coal plant. Brand name and first they told us that we are grazy their supply chain is fine....until they had to confess.

I thought that I found one cheap acryllic resin/filler composite that would have all the right mechanical properties to a cast seal in this same application....turned out that it has a little quarz and other whole lot harder paricles on the mix that first read reveals....

Pekka

[charadam]

Pekka,

Kalsiumkarbonaatti in pharmaceutical purity is available on Amazon.

But I don't know if tha Amazon empire includes Finland!

[naffsharpe (Nathan)]

Pekka, if you would like some loaded packing to try just PM an address and I'll send some FOC. As far as a "flat" format material is concerned, I would be inclined to mould solid rods of my materials into the matrix rather than an all in powder mix. Arranged in the correct order they should give the required "floating" surface? Nathan.

[gzuckier]

Could you dissolve out the CaCO3 with weak acid, to leave porosity you could fill with lube?

Sent from my SM-G935V using Tapatalk

[Fergus OMore]

I have a large tin of powdered bronze natural coloured and several coloured powders which were intended for doing gilt picture frames.

It's family stuff untouched since 1938 or earlier. Is this suitable for bearings, please

Norm

[RussellT]

I think that the Teflon/PTFE should be omitted for a dry bearing at high speeds , (it releases, I think, Hydrogen Cyanide under pressure/heat),

I think it's Hydrogen Fluoride.

Russell

[PekkaNF]

Thank you Nathan. Generous offer and interesting idea. However, need to check first the powder mix construction, have allready most of stuff for tests.

Pekka

[naffsharpe (Nathan)]

Pekka, you more than welcome to a useable sample. As is anyone else (within reason please!!).
RussellT, in that case I stand corrected, my memory was of an HSE notice from some years ago when a lot of cyanide related incidents were reported.
Nathan.