Finishing resin 3D printed parts

Safety

When sanding parts printed on an SLA printer (or polyjet printer), you should treat the dust and particles as potentially harmful—especially because these are photopolymer resins, which may retain some residual monomers even after post-curing.

Recommended precautions and PPE:

• Wear nitrile gloves and safety glasses
• Wear a lab coat or apron
• Wet sanding is strongly preferred over dry sanding to suppress dust generation.
• If dry sanding:
  • MUST be sanded in a well-ventilated area, ideally with local exhaust ventilation or a HEPA-filtered fume hood.
  • Wear an N95 or P100 respirator
  • Sanding without adequate ventilation puts others in the space at risk if they are not wearing particulate respiration.

Sanding, buffing, and polishing

• Formlabs guide
  • Formlabs recommended tools: We carry these tools in the Jacobs Maker Space
• Polishing Resin (Instructables)
• Tools recommended:
  • 3M sanding sponges (Fine, Ultra Fine, and then Micro Fine)
  • Abrasion Paste - Arexons
  • Polishing Compound

Media Blasting

• Formlabs guide

Polymer Coating

• There are a number of liquid polymer coatings on the market that provide different degrees of smoothing and chemical resistance. This can improve the overall look and feel of a part and improve UV, corrosion, and chemical resistance. They may be clear, tinted, or opaque; may be applied by dipping, brushing, or spraying; and may be based on different chemistries, such as epoxy, lacquer, and polyurethane.

1. Automotive 2K Clear Coat (Best for Durability & Clarity)

   • Recommended Product: SprayMax 2K High Gloss Clear Coat
   • Application Tips:
     • Spray light coats to avoid pooling.
     • Let each coat flash dry before adding another (about 10-15 minutes).
     • Use in a well-ventilated area or with a respirator (it contains isocyanates).

2. UV-Resistant Acrylic Clear Coat (Easier to Apply)
   • Recommended Products:
   • Rust-Oleum Crystal Clear Enamel Spray
   • Krylon UV-Resistant Clear Gloss Spray
   • Why?
   • Provides a glossy and transparent finish.
   • Easier to apply than 2K clear coat.
   • Protects against yellowing from UV exposure.
   • Dries faster but is less durable than 2K clear coats.
   Application Tips:
   • Apply multiple thin coats.
   • Allow full curing (~24 hours) for a harder finish.

3. Epoxy or UV Resin Clear Coat (Ultimate Gloss & Depth)
   • Recommended Products:
   • XTC-3D by Smooth-On (for hand-coating, self-leveling)
   • UV Resin Clear Spray (various brands)
   • Why?
   • Enhances transparency in clear resins.
   • Creates a glass-like ultra-glossy finish.
   • Self-leveling for smoothing out 3D print layer lines.
   Application Tips:
   • Epoxy coatings require a brush or dipping method rather than spray.
   • Use a UV light for UV resin sprays to cure properly.

Final Steps for the Best Glossy Finish

1. Wet Sanding (For Smoothness)
   • Start with 600-grit, then move to 1000-2000 grit.
   • Use water while sanding to prevent heat buildup.

2. Polishing (For Ultimate Shine)
   • Use Novus Plastic Polish or Meguiar’s Mirror Glaze.
   • Apply with a microfiber cloth or buffing wheel.

Best Choice?
• If maximum durability & clarity → SprayMax 2K Clear Coat.
• If easier application & good gloss → Rust-Oleum/Krylon Acrylic Gloss Spray.
• If best depth & glass-like finish → Epoxy/UV Resin Coating.

Ceramic Coating

• Formlabs article about Cerokote
• Formlabs webinar on Cerakote workflow

Adhesives to use with resin parts

Sources: Best glues for resin

• Cyanoacrylate (CA) glues (downside: hard to work with small fiddly parts)
• Gorilla 2-part epoxy (downside: can be messy)
• Hot glue gun - (downside: not the strongest bond)
• Resin welding - use a bit of resin from the printer and then UV curing (downside: fumes)

Painting resin 3D printed parts

• How to prime and paint 3D printed parts (formlabs.com)

Tiny holes and channels

• Respect minimum thickness
• Use a syringe filled with alcohol