Making your 3D prints look like...not prints

On all the other printed guns I've made, namely my SCR style bolt action AR, my half printed STI style 1911, and my VZ-61, I shamelessly left the 3D prints looking like 3D prints.  After all, that was the point, to make printed guns.  My PSG-None project is different though.  It's intended to be a "stand back and squint" clone of an HK PSG-1.  I'm using printed parts for all the furniture, but I don't want them to look like obviously printed parts.  

Since I have a variety of parts, I'm going to use a variety of techniques to finish them.  All my parts are printed in black so that if/when they get scratched or dinged up, they will scratch to black and it won't be visible.  If you print in bright orange and then paint it black, when scratched the bright orange will show through and be super obvious.

The first and most basic method is to just sand down your parts so that there are no more layer lines.  For this to work, your part has to be printed in the color you want, or you'll have to prime and paint after sanding.  I prefer just printing in color.  I always use wetsanding for plastics.  Dry sanding is fine for rough 80-120 grit paper, but any finer than that, and the sanding dust can melt from the friction and gum up your sandpaper.  For the palm rest on my PSG-none, I knocked it down with 80 grit dry, then wetsanded 320 and 600 grit(because that's what I had handy), then finished with a Mr. Clean Magic Eraser which is equivalent to 3,000 grit sandpaper.  There are still a few scratches showing because I'm lazy.  Since PLA is largely immune to most solvents, once dry I wiped it down with my preferred gun oil to "wet" the surface and make it a little darker.

The next method is very simple and kind of like magic.  I wanted to make some parts look like HK's textured molded plastic.  Normally this would be almost impossible to replicate, but I know of a product made just for that.  SEM 39853 Texture Coating is a spray on automotive product primarily aimed at auto repair stuff like textured plastic bumpers, dashboards, etc.  It's made specifically for plastics and bonds very well to PLA.  The first step is to knock down the high spots with 80 grit sandpaper, that's it.  If your print is clean, you don't even need to do that much, Texture Coating hides layer lines great.  

Next, spray on the SEM Texture Coating.  You can make a wide variety of textures from very fine to very rough, depending on how heavy you spray, and from what distance.  Once dry, it can be topped with paint of your choice.  My preference is SEM Colorcoat.  It's also an automotive oriented product and is made specifically for plastics, fabrics, and vinyl, and is very durable while still being flexible(if that's what you need).  It's durable enough that the steering wheel of my daily driver was painted SEM grey 7? years ago, and it hasn't worn off yet.

The last method I'm going to show is the hardest to do, and I am not very good at it.  I want to make the grip handle look like wood.  Some people are simply amazing at this technique, I...am not.  We'll be using artist's oil paints for it because they blend very well.  I started out with a base coat of brown spraypaint.  Once that was dry, I covered the textured part of my grip with a thin black wash to darken up the low spots in the texture.

Next is where the magic is supposed to happen, but again, I'm me.  Artists oils are basically just pigment suspended in Linseed oil, so they're not that much different from what you'd use on a wood stock.  A cheap set of oils is $13 at Hobby Lobby, and if you use their weekly 40% off coupon(downloadable on your phone straight from their website), you can get a set for $8.  Using a combination of Burnt Umber, Burnt Sienna, and Yellow Ochre, the idea is to basically paint on the woodgrain.  As I said, I am not good at this.  This was only my second attempt, and I'm colorblind, so that's a big help...  Since I suck at this game, my method was to basically just put on streaks of color and blend them out so it looked less uniform.  My brush strokes go the same direction as my print layer lines to help hide the print lines without having to sand them down.  The paint it's self isn't super durable so after a month or two(or more, raw Linseed oil takes forever to dry), it can be top coated with an oil based polyurethane for durability.  I'm not really satisfied with how this turned out, but I guess it will do(and the sharp streaks on the bottom will be covered by the palm rest shown above).