Finishing a 3D Print

Achieve a silky smooth finish on your 3d Prints! I’ll be using a mask I made as an example, though this method is applicable to most 3D prints as long as they aren’t too small or detailed since finer details will most likely be lost in the process.

● A 3D print, preferably in PLA or another softer plastic but it will work with other materials (Make sure it has thick walls to allow for sanding)

● Various grits of sandpaper from rough to fine.

● A can of filler primer, I used Rustoleum brand (you don’t need the sandable kind)

● Paint, spray paint for the best surface finish

Since sanding plastic is harder than sanding filler primer, you don’t have to get the part perfectly smooth now, just get rid of the worst of the ridges from the printing process. Starting with your roughest grit sandpaper, sand in an elliptical pattern against the direction of the ridges. Once you get it as smooth as possible, move up to a higher grit. Repeat the process until your part is nice and smooth or you get sick of sanding. You can see in the picture that my part was still fairly rough when I moved on to the next step, but I was still able to achieve a very smooth finish.

Take that can of filler primer I told you to buy and absolutely hose your part down with it. They tell you to apply light coats, but that’s a lie. Just completely cake that stuff on. The purpose of filler primer is to fill imperfections and by golly we’re going to do just that.

Once the primer is dry, get a bucket of water or just hold your part under a sink and wet sand the primer back down to the surface of the part. Having a continuous flow of water either form a faucet or dunking in a bucket makes the primer really easy to sand. Use a medium grit sandpaper and very carefully sand down the primer, since the primer is so soft it’s very easy to accidentally remove it from the grooves and flaws you were trying to fill in.

Prime your part for real for this time. Since this is the final coat of primer, we want the highest quality finish on it that we can manage. You can either use the same filler primer from earlier or regular primer, but either way, actually follow the instructions on the side of the can about applying multiple light coats. When the primer is dry, lightly wet sand it once more with a high grit sandpaper to achieve the smoothest possible finish.

Make it look real pretty. To avoid brush strokes, I recommend using spray paint; apply several light coats letting the paint at least partially dry in between to prevent the paint from pooling up and causing drips.