A special part of me enjoys it when people go ‘I cannot believe that was 3D printed’ and one of the best ways to get that reaction is through post-processing. Now not to belittle the beauty of a raw print result you can achieve from a correctly dialed in fused filament fabrication 3D printer. I love this too but you won't be able to get mirror/automobile finishes from it. This will go through the process I go through to get nice useable finishes that you can hold and touch and not be concerned about it rubbing off. It will be excellent for final statue pieces or for clamshell cases.
This guide is going to focus on exactly how I have been post-processing my components with paint to produce long-lasting end finishes that will not rub off after extended use. An automobile finish is what I was going for. I use spray paints but there are many methods (airbrushing comes to mind) and other paints you can use (give a marble or metallic results) and that will be explored as well. Post-processing with paint takes time so patience is required in each step of this workflow. It is good to be doing other things at the same time so you don’t catch yourself watching paint dry. Contents of this guide can be seen below.
- Before and After Shots
- What You Need
- Workflow
- Images from Every Stage of Workflow for Clamshell Case
- Other Paints and Post-Processing Methods for 3D Printed Parts
- Acknowledgements
You can post-process stunning results from average 3D prints but it is definitely easier if you are already producing excellent components straight off the print platform. If you want to consistently produce amazing components come check out the guide Improving 3D Printed Model.
As always if you have got any questions, queries or things you'd like to see added please let us know your thoughts!
Before and After Shots
Below is a clamshell case for a handheld electronic device, left is before, right is after. This is the part that I will go through the process of cleaning and making really. Further below I will have other examples of post-processing 3D printed parts with different colours of spray paints.
What You Need
Below is exactly what I used to post-process this automobile finish for the clamshell case.
- 280 and 400 Sandpaper. (The More the better, Nothing worse than running out)
- Prime and Putty all in One Repair Spray
- Paint and Prime Black Spray Paint
- Gloss Clear Spray Paint
- Wire Tray or Cardboard to paint/let the component dry on
- Mask
- Gloves
Workflow
This is the exact stages that I have gone through to post-process this clamshell case to have an automobile finish. This clamshell was printed using CPE + but the process I describe below will work on almost all readily available 3D print material. So long as the material is sturdy, capable of being sanded and allows primer and spray paint stick to it you can have the same result.
Good spray paint technique involves wearing gloves and mask, shaking the can for 5 minutes (shake until you think it is good then shake it some more) and spraying in an arc from 45 cm + away from the component. It is so easy to switch off and spray too close but that will put too much paint on the surface. Each layer should only be thin and you should be able to see the previous layers behind it when a layer is done. This will enable a nice depth to the surface as you will be able to see into the layers of the piece. It will also prevent details of the actual component being lost. If you spray to heavy then you can normally sand it back, although for some models you can lose details doing this too many times. If bulbous liquid drops form on the surface of the component or if droplets are running off the component that is an indication that a layer is too thick. You can always sand back material so just wait and sand it back. Patience is rewarded hugely in this process.
Stage One: Initial Sandpaper to help the first layer of primer to stick. 280 Grit is a good starting point.
Stage Two: Three Layers of Primer Putty. 2 Hours of drying time between layers. Each layer sand back aggressively except for the last.
Stage Three: For the final Primer Putty Layer grab a fresh sheet of sandpaper fold it to be flat and use that flatness as a way to sculpt the component to exactly how you want. Do not be aggressive with this final sand and use 400 Grit.
Stage Four: Three Layers of Black Paint and Prime Spray Paint. 1+ Hours of drying time between layers. Each layer sand aggressively except for the last using 400 Grit. Each layer needs only be very thin. The more layers showing through the deeper and more beautiful the final result. The final layer of this black spray do not sand.
Stage Five: Two Layers of Gloss Clear Spray Paint. 1 Hour of Drying time between layers. This will protect the layers underneath and give a really nice sheen. Sand back the first layer lightly with 400 Grit and then do not sand the final layer.
Stage Six: Once the final layer is on bring it to an Airy and Dust-free environment. Leave for a day until paint looks dry (it will still be mushy so do not touch the surface yet)
Stage Seven: Take it outside in a semi-shady area and let it dry for 4+ days. If it is in the Sun all day this will speed up the process. Do not let rain get on it though. Then the post-processing will be complete.
Also worth knowing, at every layer, it is important to wait until the surface is dry enough to work with. This will usually take an hour or two given a cool night with a light breeze. Spray paint can be deceptive and look dry when it is actually wet. Shine a flashlight on the part and that will reveal whether it is wet or not. Now that hour between layers is enough to work on the component but the layers are still mushy and prone to fingerprints marring the surface. So for the final layers between colours don’t sand or touch the painted surface. Multiple layers will take days to truly cure and dry so keep it in an airy and dust-free environment for the first day then place it outside where the sun can seal and completely solidify the paint. Wait as long as you think you need to then wait twice as long. Patience will be rewarded.
Images From Every Stage of Workflow for Clamshell Case
Below are images from Stage 1 - One image of it Printed on the Build Platform, both sides were printed at the same time. Two images of it Raw from the Ultimaker S5 3D printer and one image of it sanded. I utilised Ironing to make a smoother top surface which saved me a lot of initial sanding and post-processing.
Below are images from Stage 2 - Two images from the first layer of the primer sanded back. One Image of the last layer of primer just put on.
Below are images from Stage 3 - One image of that final layer sanded back with the intention of sculpting the final shape. Two images of the clamshell case put together and then sanded to improve the fit.
Below are images from Stage 4 - Two images of the first black spray paint layer where you can see how lightly it has been painted. Two images of the clamshell case put together and then sanded to improve the fit even with the spray paint on. Really shows the layers forming. Two images of the black spray paint second layer sanded back aggressively. And an Image of the final layer of black spray paint wet on the clamshell surface which was not sanded which is emphasised by a flashlight.
Below are images from Stage 5 - Below is an image is the first layer of Gloss and Clear Spray paint. Unfortunately, my photography skills decreased for this layer. This was sanded back lightly and then another layer of gloss and clear was sprayed on.
Below are images from Stage 6 - Here is an image of the final coat of Gloss and Clear drying in an airy and dust-free environment. Very wet at this point.
Below are images from Stage 7 - Below is three images from the next day of the clamshell in the sun. Looks dry but I assure you it is still very wet. No touching allowed for me till a week later.
Complete - Below are two images of the Final Piece All dried and done.
Other Paints and Post-Processing Methods for 3D printed Parts
There are lots of spray paints and colours you can use (just ask your local hardware shop) using this method. So long as you have a good couple of final layers of gloss clear coat for materials that you can grab the world is your oyster.
Airbrushing is definitely a fantastic way to get excellent results as well. And Acrylic paints can give an excellent effect like in the images I will show below. You can also fill your 3D printed models with Sand or other material to make them heavier. This will trick people into thinking they are made of stone or some other heavy material.
Acknowledgments
This clamshell case design is a modified design but was originally a G-Wii Rev 1 designed by G-man himself. Him and the rest of people at Bit Built and their forums create the most stunning homemade portable devices in the whole world! Ripping hardware from consoles, reverse engineering, producing custom circuit boards and miniaturising everything. I love those guys hope they keep crushing it.
