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Finishing surface of clear resin (like glas)

Hello community,

do you have some experience in getting the clear material really clear (like glas).

Do you have any tips for finishing the parts (look at the pictures)?

Or do you any knowledge in mechanical or chemical finishing the clear resin to make this really clear?

Many Thanks

Stefan

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I have spent a lot of time and effort on this very subject. You’ll notice that the clear resin models are in fact clear during the build and when you rinse them in isopropyl alcohol. When they are wet, they appear clear. When they dry out though, the surface looks just like your models.

I was intrigued by the article on hackaday.com that refers to a surface smoothing method using vaporized solvent. See http://hackaday.com/2013/02/26/giving-3d-printed-parts-a-shiny-smooth-finish/. To test out the process, Since I don’t own an ABS printer, I used a lage candy jar on a hotplate to smooth scratched Plexiglas with methylene chloride. It worked like a charm! Unlike the ABS plastic models they refer to in the hackaday article that are soluble in acetone, our photo polymerized acrylic FormLabs models are resistant to pretty much any solvent. (I went to a forensic laboratory myself and tested the solubility of supports in test tubes with about 20 solvents, some quite exotic and most very dangerous to work with. No appreciable solubility occurred with any chemical.)

I tried polishing the models with a variety of pastes and fine abrasives. Polishing kind of works, but it’s nearly impossible to work in small recesses and friction heat is a huge problem.

What turned out to work the best is Kylon acrylic spray. I put my models on a record turntable and just spray the models with an even coat of acrylic spray as they slowly spin. Sometimes two coats are necessary. It fills in all the minute gaps on the surface and amazingly, the model is clear again like when it was wet. Too simple…

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Hey Daniel,

Thanks for your comment. Have you any picture of the result? When did you spray the part? Right after the iso bath?

Thanks

I’m still trying to print the model correctly (waiting for my 2nd replacement printer after FL proves that they can print it on the Form1+), but I think that you’ll get the idea from this early print.

Nice! And thanks again!

I forgot to address part of your question. Wash the part thoroughly in isopropyl alcohol and let dry completely before spraying on the Krylon. You can use the Krylon acrylic spray with UV protection and the part won’t yellow as much if it gets sunlight.

Stefan,

For large flat surfaces like you show in your first picture, the easiest way to make a nice clear surface is hand polishing. Wait a few hours after washing the part in IPA to make sure it is completely dry and then polish as you would acrylic. Start with a rougher grit sandpaper and then wet sanding up to ~2000 grit before finishing with Novus 3,2, and 1 (follow the instructions on the bottle). Depending on your part’s orientation (and layer thickness) you may want to start anywhere from 220 to 800 grit, but the goal is to make a uniform surface before advancing to the next grit and don’t rush right to 1200 or 2000. We’ve also had good luck doing a final polish with mineral oil instead of Novus 1 or even using oil instead of water during “wet” sanding.

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An alternate idea, which can look amazing, but is a more challenging (and dangerous!) technique is to place a thin coating of clear resin on your flat surface, then cover with a thick pieces of clean glass. You cure this layer of resin through the glass using a 405 nm laser pointer (or leave it out in the sun). The part will become very strongly adhered to the glass, but if you can remove it, the surface will resemble the glass it cured against. But be careful of cracking the glass!!!