How Smooth can I get a 3D Print with Sharp Edges?

I have a 3D scan of a rather large (approx. 39mmx39mm) gemstone that I plan on printing.

I originally planned on having one cut from CZ, but it's not exact enough, plus it lacks consistency for what I need. Does anyone here have experience with smoothing out 3D prints with sharp edges? If so, what are the best methods and what are the results?

I considered getting it printed in smoothest high detail frosted plastic, and also fine detail plastic, moulding with silicone, casting in resin, then sanding with varying grits until I get a real smooth finish, then applying a topcoat of gloss. Obviously I'd be casting these in colored clear resin with tint in the end to achieve a more proper "crystal" look, but I'm sure you all get the idea!

Thank you in advance to anyone willing to help!!

Sandpaper. No shortcuts for perfectly smooth and perfectly sharp corners.

Put the sandpaper on a block or glued (spray adhesive) to a plate of glass so your sanding surface is flat, then carefully sand the facets with increasingly fine grit. If you're going to cast them, filler primer will save you a lot of time on sanding. In that case, rough sand with pretty coarse grit, filler primer, then wet sand with high grit.

ABS will also make your life a lot easier on the finish side.

FlowerPower said:

Sandpaper. No shortcuts for perfectly smooth and perfectly sharp corners.

Put the sandpaper on a block or glued (spray adhesive) to a plate of glass so your sanding surface is flat, then carefully sand the facets with increasingly fine grit. If you're going to cast them, filler primer will save you a lot of time on sanding. In that case, rough sand with pretty coarse grit, filler primer, then wet sand with high grit.

ABS will also make your life a lot easier on the finish side.

Click to expand...

Thank you!


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How many facets are we talking? I went through this in my Krull glaive, and it was nearly impossible to sand a 30mm gem with nearly a 100 facets; you invariably end up rounding down the sharp edges.
I would personally look in the high detail as you mentioned (Shapeways is an option) and molding and casting. If you are considering going that route, take another look at your scan to make sure the resolution will make it worthwhile. I've had scans that were INCREDIBLE on resolution, and others that were not so hot; a printer (no matter the settings) can't print more detail than the original model has.
Good luck with your project! Too bad you can't find a gem that's already manufactured :rolleyes

FlowerPower said:

Put the sandpaper on a block or glued (spray adhesive) to a plate of glass so your sanding surface is flat, then carefully sand the facets with increasingly fine grit.

Click to expand...

This! Glue your sandpaper to a very flat surface that does not flex. It makes all the difference.

no matter what with a printed object your "sanding" it down to a smaller and smaller size from your original print measurements. i agree with everyone above that gluing your sandpaper to a piece of glass is best if your hand sanding, but YOU HAVE TO COMPENSATE for ALL the material your sanding away for the size to remain true to your original "size". just my 2 cents tho..

laellee said:

How many facets are we talking? I went through this in my Krull glaive, and it was nearly impossible to sand a 30mm gem with nearly a 100 facets; you invariably end up rounding down the sharp edges.
I would personally look in the high detail as you mentioned (Shapeways is an option) and molding and casting. If you are considering going that route, take another look at your scan to make sure the resolution will make it worthwhile. I've had scans that were INCREDIBLE on resolution, and others that were not so hot; a printer (no matter the settings) can't print more detail than the original model has.
Good luck with your project! Too bad you can't find a gem that's already manufactured :rolleyes

Click to expand...

Well, I've yet to count the bottom facets but the top has 39 total.

Like I said the gem is rather large, 39-40mm. I found some resin gem tutorials online and some of them come out looks absolutely amazing. I just may do it instead of having it carved and then casting that. I think if I tried enough times that I could get to look nice. I will say though, I'd probably have to cast the 3D print in solid resin and then carve, that way the print lines don't go deep. The resolution on the file is perfect. Large file, smooth as glass all around. Thank you!! I'm sure I'll make a post on here about it when I get it done haha.

funboy1013xx said:

no matter what with a printed object your "sanding" it down to a smaller and smaller size from your original print measurements. i agree with everyone above that gluing your sandpaper to a piece of glass is best if your hand sanding, but YOU HAVE TO COMPENSATE for ALL the material your sanding away for the size to remain true to your original "size". just my 2 cents tho..

Click to expand...

Will do! That is a good tip and one that I did not think of haha.