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Good afternoon, SF. I'm here with an odd (maybe) question. My company builds a product that uses a cylindrical component machined from a thermoplastic material called XP-109. As I understand it, it's roughly 1/3 PEEK, 1/3 carbon fiber, and 1/3 Teflon. Here's the material: www.tinyurl.com/y6hwxqjk Anyway... we have to polish the end of this cylinder (roughly an inch in diameter) to nearly a mirror finish before assembly. We're getting better at it, through a series of increasing-grit sandpapers and then a ceramic, but we're at that plateau now where we stop and realize, "there must be a better way. We just haven't figured it out yet." So. Has anyone here got experience polishing such materials? Can you share your experiences and methods? Thank you all. God bless America. | ||
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Nosce te ipsum |
Micro-Surface Finishing Products Inc. of Wilton, Iowa should be able to help. They make an abrasives kit for overhauling military helicopter engines, kits for fine art restoration, and I use them to put a mirror shine on ebony fingerboards (the 1,500 - thru - 12,000 grit buffing sticks). https://micro-surface.com/micro-mesh-types FAAA-cinating company history: https://micro-surface.com/who-we-are | |||
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Lost |
Progressive polishing is how we processed fiber optic terminations, pretty much how you're doing. This was true for plastic fiber/ferrules as well as glass/aluminum. However, I don't know that this is the only or best way. One other method depends on the material you're polishing, and that is cleaving. Some materials, like glass and some plastics, can be cleaved to a perfect optical surface. I have no idea if the PEEK material you're using would work. | |||
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| Just because you can, doesn't mean you should |
I think this may be something best done in a mold, requiring a shiny surface, so they come out with the correct finish and don't require more processing. ___________________________ Avoid buying ChiCom/CCP products whenever possible. | |||
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| Nosce te ipsum |
https://www.novuspolish.com/fine_scratch_remover.html Novus 2 puts a gloss on most plastics. I’ve used it as a final step at times. | |||
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| Member |
I understand what you're saying. You can get a good, smooth finish from some molding operations, for sure. The thing is, the finish we have to have on this end of the part is just about glass-like. One of our crew said the finish is actually better (smoother) than auto glass when done right. We've been running a polishing operation on a lathe sometimes, with moderate success. One of my team has built a standalone polisher and had good success with it, but even so we're thinking there's a better method.
Thank you for the links, Woodman. God bless America. | |||
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| Lost |
Maybe a lapidary rig of the type used for gemstones? We used very similar setups for optics. Started with coarse through fine abrasive papers, then finished with an abrasive slurry pumped over the wheel.  | |||
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| Member |
That's a good thought. Thank you, kkina. God bless America. | |||
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| Member |
I did a fair bit of polymeric and FRP materials polishing for microscopy purposes during my MS and PhD. We used progressive polishing eventually using diamond paste suspensions. We used Buehler products (https://www.buehler.com/). I’m sure technology has advanced since then, but I’d look at a progressively finer and lower volume fraction of particle suspensions. Be careful with the force and rotational speed (I’m assuming you’re using a polishing wheel) you apply as you may have issues with fiber pullout, especially since you won’t have chemical bonding with the PTFE. Let me know if you have any question. I’m no tribologist, but I’ll do my best. | |||
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Don't Panic |
What's the purpose of the shiny finish? Is it functional, or just appearance? | |||
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| Nosce te ipsum |
In my jewelry hobby of yestercentury, turning silver, gold, and platinum into scrap metal, I also used a diamond grit buffing compound. Red rouge was softest, then a dirty white compound, and hardest was grey star, I think it was called. A 1/6 h.p. bench grinder with a tapered spindle attachment for the 4” buffing wheel. The wheels came in different densities as well. A dense wheel with the grey would cut fastest. The fluffier wheel with red was for final polish of soft metals. | |||
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| Member |
Good question! It's functional. Without being so specific as to get myself in trouble (IP and all), it's part of a "water bearing" arrangement. It's got to be "hella smooth." Here's a twist: we may not be able to use some bottled polishes/suspensions, for fear of not getting the part completely clean afterward. The part has to be free of any debris/grit/residue before going into the assembly. Kampy, thank you, I'm headed to Buehler's site next. God bless America. | |||
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| Nosce te ipsum |
You're welcome! Glad to help. The 3" x 4" set might be a decent tester; after you home in on the most frequently-used grits, you can order only those. I have used the buffing sticks and smaller pads for several years, purchased from woodcraft and internationalviolin mostly. The sets make great gifts. The Novus has been used on plastics, metals, lacquer, varnish, lots of surfaces. It has blended in more than a few of my errors. MICRO-MESH 3" x 4" Polishing & Finishing Pads - 9 Grades - Made in USA https://www.woodcraft.com/prod...-touch-sanding-pads# https://www.internationalvioli...sandpaper-steel-wool   | |||
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| Member |
Yes, I start with Novus 3 if really bad, then novus 2, and then novus 1......novus works really well on plastics for polishing out scratches. | |||
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| Nosce te ipsum |
Is a wipe-down with a naphtha-dampened lint-free cloth a possibility? | |||
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| Member |
That's a good question, Woodman. I need to check with our EHS (Environmental, health, and safety) peeps and see if naphtha is allowed in the facility. God bless America. | |||
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| Triggers don't pull themselves  |
As others have mentioned, progressive grit papers/polishing compounds are the standard practice. Since the material is partially thermoplastic it’s possible that heating to near the melting point with a handheld torch might achieve an improved finish. However, PEEK and PTFE have very high melting points and the carbon fiber adds another variable in addition to the safety issues having an open flame brings. Michael | |||
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