Professional Guide to Finishing and Painting 3D Printed Parts

High‑strength continuous fibers and the fine surface finish of Onyx make Markforged parts ready for many applications. When a different aesthetic is needed—whether for a Halloween prop or a polished prototype—proper finishing and painting can elevate the look and durability of the part.

Finishing Your Part Before Painting

To achieve a smooth, paint‑ready surface, follow these steps:

1. Remove Glue Residue
   After removing a print from the build plate, wash off any glue left on the part with water. Dry thoroughly before proceeding.
2. Trim Loose Filament
   Use wire cutters or tweezers to clip or pick up strings and blobs caused by low‑angle overhangs or material inconsistencies.
3. Wet Sand the Surface
   Use 220‑grit sandpaper while wetting the part. This smooths layer lines and eliminates scratches. If your part contains carbon fiber, work in a well‑ventilated area and wear a mask.
4. Remove Dust
   After sanding, scrub the part with a wet brush to lift fine particles. Once dry, wipe with a tack cloth to remove any remaining specks.

Spray Painting

Spray paint designed for plastics—such as Rust‑Oleum or Krylon—provides excellent adhesion to nylon and other Markforged materials.

1. Select the Right Primer and Paint
   Choose a plastic primer and a corresponding spray paint. Primer seals the surface and prevents excessive absorption.
2. Work in a Ventilated Area
   Use a fume hood or spray booth. Wear a respirator and gloves for safety.
3. Set Up the Part
   Hang the part on a wire or place it on a stand to expose all surfaces without flipping. If only a section will be painted, mask the rest with painter’s tape.
4. Apply the Primer Coat
   Follow the manufacturer’s instructions for distance, number of coats, and drying time. After the first coat dries, rotate the part to cover the backside.
5. Apply the Finish Coat
   Spray the paint in thin, even layers. Avoid drips by maintaining the recommended distance. Rotate as needed for full coverage.
6. Dry and Cure
   Allow the part to dry per the paint’s guidelines before handling.

Hand Painting

For more detailed or artistic finishes, hand painting offers flexibility. Acrylic paints work well with nylon and other polymers.

1. Choose the Paint
   Select an acrylic paint that meets your color and finish requirements.
2. Primer First
   Apply a plastic primer to reduce paint absorption and improve adhesion. Let it dry completely.
3. Paint the Design
   Use brushes or fine tools to apply the acrylic paint. Work in a well‑ventilated area and allow each layer to dry before adding the next.
4. Final Drying
   After the last coat, let the part cure as directed before handling.

Ready to try your own painted part? Download our sample mask and pumpkin files here. If you don’t have a Markforged part, request a sample to experiment with.