How to Paint 3D Printed Parts
Finishing Resin and Polyamide Parts
Take a minute to read the instructions on the specific can that you will be using. There should be information about how far away you should hold the can from the object that you are painting, as well as how long to wait in between coats.
What You Will Need:
- Wet/Dry Sandpaper, 320- 1000 Grit
- Running water
- Microfibre cloth
- Sanding Block
- Krylon Paint
- High Fill Primer
- UV Resistant Clearcoat
- Paint Respirator
- Bondo Filler (optional)
And Parts Produced By:
Important Tips Before You Begin:
Spray In Sweeps
To ensure a consistent finish, paint by sweeping the paint can horizontally and vertically past the object. If you are painting from left to right, then begin spraying to the left of the object, sweep the can along the object, and continue spraying until you are past the object on the right.
Do a Pattern Test
Spray a test onto a piece of cardboard test before commencing painting. This will help clean any debris from the nozzle. You may need to adjust the distance between the can and the object to obtain the most desired spray pattern depending on the paint being used.
Start Smooth - Finish Smooth
The quality of your final part depends on the quality of your sanding. Spray painting produces a smooth surface which tends to reflect light and make surface blemishes very apparent. To ensure a smooth painted finish you must start by properly sanding and priming your parts.
STEP 1: Sanding
Sanding is the most important step in the entire process, requiring the most amount of labour. PolyJet, SLA and SLS parts come out of the printer with a relatively smooth surface, however they may still require some hand sanding to remove support blemishes. Parts produced using FDM or FFF technologies will require much more rigorous sanding. If any holes or gaps cannot be sanded down, we recommend using Bondo filler.
Start sanding using lower-grade 320 grit for initial sanding. Progressively move towards finer sheets of sandpaper to smooth the part surface and get it ready for priming.
Defects in parts should be sanded out in this stage as much as possible, otherwise they will become more noticeable after the paint is dry.
Minimize visible stepping in parts as much as possible by sanding against the grain.
Tips & Suggestions
- The part should be smooth to the touch with no rough surfaces left over from support
- Attend to areas where the print switches from glossy to matte, it is the most likely place to find defects
- Pay attention to upward & downward facing sections of SLA where stepping may be most noticeable.
STEP 2: Priming
You will need to apply a few coats of primer to ensure that your part is ready for painting. Follow the instructions on the spray paint can and apply the spray in a sweeping, consistent motion. You want to avoid applying too much primer to one location, while also ensuring that all of the part is coated. It typically takes at least 3 thin coats of primer to fully cover a surface. A black primer is ideal for painting with darker colours, while white is ideal for lighter tones. We suggest using a high fill primer, which will make your life much easier.
Begin by applying one coat of primer and letting it dry completely. Priming will highlight areas where the part may require additional finishing. Using 1000 grit sandpaper, lightly sand the model between coats of paint which will help to further refine the surface. Remove dust and polish with a microfiber cloth. This is recommended after each additional coat of primer.
Be sure to let each the final coat of primer dry completely before moving each coat. Rinse the model with water and dry before moving on.
Tips & Suggestions
- Priming will highlight any areas on the model where additional finishing may be needed as well as cover up other issues.
- Be careful to avoid drips and puddles
- If pooling of paint occurs, wait for it to fully dry before sanding it down.
STEP 3: Painting
Apply a few coats of paint to ensure a consistent, durable finish. Ensure that the paint has dried completely on one coat of paint before you apply another coat, refer to can for drying time instructions. Apply several thin coats of finish paint. Between coats, buff and polish the paint surface for glossy
If defects become apparent during this stage, you will need to go back to the sanding and repeat steps 2 and 3. Between coats, remember to buff and polish the paint surface. This maintains a smooth surface that will look glossy under the final clearcoat.
While more coats will make the paint more durable, be careful not to add to many coats as it can affect clearances on mating parts. More is not necessarily better.
Tips & Suggestions
- Ensure part is clean and dry. Use a microfiber cloth or compressed air to remove dust
- Blemishes may appear in areas where support was no completely removed. You may need to go back to step 1.
- Avoiding over-painting mating surfaces as it may affect clearances
STEP 4: CLEARCOAT
Stereolithography, SLS & PolyJet materials are compatible with most plastic coatings, such as acrylics and lacquers. Select a UV resistant final lacquer-based clear coat with the desired finish, either glossy, semi-gloss or matte to further increase the longevity & wear resistance of your finish. Using one of these coatings will give your printed part either a consistent finish in either as well as provide additional protection against scratches, chips, and other marks.
Before rigorous handing, ensure the part has had sufficient time to dry. We recommend at least 24 hours after the last coat has been applied to ensure the paint is sufficiently set.
Tips & Suggestions
- Spray thin coats to prevent pooling
- Ensure the part is completely coated to help shield the resin from UV damage and give it a nice even finish.