Introduction: Post-processing 3D Printed Parts

This instructable was originally published on my blog on November 29, 2020.

3D printed parts are often rough and uneven, and I found the perfect project to learn as much as possible about how to post-process them.


I chose the new version of the Tesla Roadster and found two 3D printable models:

  1. Roadster by linuxpenguin7 on Thingiverse
  2. Roadster by SIM3D_ on Cults3D

While the first one is free, it lacks details like the form of the front lights, the softness of the angles of the car, the rims, among others.

The second one is paid and was not made to be printed, but it has every little detail of the original car.

Both are perfect models and both have some cons, but because I wanted to print the car as big as possible, I went with the one with more details.

Step 1: Part 1: Glue

The first step of building it was bonding all the 3D printed parts together.

I used aggressive 60-grit sandpaper to prepare the surface and fast-dry epoxy glue with a hardener to join the parts. Then I cleaned up the excess of glue using isopropyl alcohol (IPA) to prepare the car for the next step.


  • 60-grit sandpaper
  • 2 part epoxy glue
  • Isopropyl Alcohol (IPA)
  • Filament: Prusament PLA in Galaxy Black, Azure Blue, and Lipstick Red.

Step 2: Part 2: Sanding and Puttying

Preparing a 3D printed model to paint is a very long process. I sanded it using 5 different grits progressively and then repeated the process after applying glazing and spray putty.


  • 80, 120, 240, 400, and 1000 grit sandpaper
  • Glazing putty (Bondo)
  • Spray putty


  • Dry sand using 80, 120, and 240 grit sandpaper.
  • Wet sand using 400 and 1000 grit sandpaper.
  • Apply glazing putty (Bondo) to the most uneven parts.
  • Wet sand again using 400 and 1000 grit sandpapers.
  • Apply spray putty, wet sanding with 1000 grit sandpaper between coats.

Step 3: Part 3: Paint

Although I thought it was gonna be a quick project, it took me months to finish.

I spray painted it with two coats of white primer. Then, I applied 3 coats of metallic red and immediately sprayed the 2-layers clear coat.

The windows were painted with glossy black and a clear coat as well to get more shine. The bottom of the car and some details were painted by hand with matte black. Everything was put together with super glue.


  • White primer
  • Metallic red: Dupli-Color Auto Color code 50-0170
  • Red paint for calipers
  • Clear coat: 2-Layer Clear Varnish Automotive Spray Paint
  • Super Glue

Step 4: Conclusion

The main purpose of this print was to learn to post-process 3D printed parts, but it evolved to also understand the constraints of printing a 3D model that was not created to be printed.

Although this is an extremely high-quality and beautiful 3D model, it needs extra work to be 3D printable. For example, all the windows and lights were printed 1% to 5% smaller than the originally intended size because otherwise, they don't fit.

The parts needed a gutter between them, and these were exact to the millimeter which is not accurate on physical objects. The same with the wheels and brakes: I drilled the holes to be 1mm wider to fit everything together.