I was looking at trying my hand at doing some detailed finishing of a 3D print. Since most 3D printers lay material down in small layers (.3 mm) the print has a layered and striped look. With ABS prints you can soften the layering the effect with acetone. The acetone will dissolve the plastic a little bit before evaporating, thus smooth over the layers. Too much acetone will leave the part a bit droopy looking. But with PLA that process is not as easy. And larger prints come out looking better with PLA (more uniform, less shrinking, less warping). Also a friend of mine was looking to try to apply a mirror/chrome finish to a 3D print and I knew exactly the model I wanted to try some finishing techniques on.
Enter the Trimaxion Drone Ship from the 1986 ‘Flight of the Navigator’
Here is the trailer for those who don’t know.
In the movie the ship was mainly CGI. But that shouldn’t stop me.
I found a model of it here.
http://www.thingiverse.com/thing:357472
I would describe the shape as a silvery stretched out acorn squash. I liked the shape because it was simple, symmetric, smooth for the final product, and clearly defined lines. I knew there was going to be a lot of sanding and I didn’t want to worry about sanding small holes or something.
The print came out in two parts. And even through I printed it out in PLA there is still a little warping. So the first step was to sand down the two meeting faces to make them flat as possible and then glue them together. After I glued them together I applied some automotive body filler (Bondo) to fill in the crack. After the bondo set I sanded with 100-200 grit sandpaper. The first pass is below.
After that I did some wet sanding with 400-500 grit sand paper.
Next step was to apply some primer.
After that the process is wet sand-prime, wet sand-prime…
In the pictures below you can start to see the lines disappear. But still more wet sanding and priming.
And below I’m starting to get to what I want.
And finally I did one last wet sand with 1000 grit sand paper. I painted it with a three coat system from spaz stix. You start off with a back coat, in this case black, then apply the chrome paint, and finally a clear top coat.
Here is final product.
Lessons or what I would have done differently.
- Start with a slightly larger model. This wasn’t too bad, but a little bigger would have sanding the lines a little easier.
- More coats of bondo or other filler. I only used one coat of the two part bondo. They also have a one part that is meant for smaller details. I would have used the two part mix for the gap between the two sections. Sand that, then applied the one part over the entire thing. I think I spent too much time trying to fill in with primer.
- Use more filler primer. There is a type of primer that leaves thicker coats of primer. Again, save time on paint-wet sand cycles.
- More gentle with the final paint coat. I was using spray cans and that can be a little difficult to regulate the amount of paint that gets applied. Spaz Stix has jars you can get that you can use an air brush to apply the paint.
- Take more time between coats of paint. When I was finishing with the top coat a small pool of paint formed on an edge. That pool dissolved everything down to the primer. Also I marred the surface a little when I was moving the model to paint the underside.
Overall it was a simple project. I got to learn some of the basics and will inform me on my next project.