Gallery, Projects and General > The Design Shop
Epoxy matrix bearing material DIY
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!
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