How to Sand UV-Resin and FDM 3D Prints Safely: Dust Control and Post-Cure Tips (220–2000 Grit Guide)

Whether you print parts on an SLA resin printer or an FDM filament machine, sanding is the bridge between raw print and professional finish. But the two materials behave very differently—resin dust can be toxic, and thermoplastic layers melt if overheated. Here’s how to sand each type safely and effectively.

Why Technique Differs Between UV-Resin and FDM

UV-resin prints cure through photopolymerization, forming a brittle surface that powders when abraded. FDM parts, in contrast, are thermoplastics that soften with friction. Matching grit, pressure, and cooling method to each material ensures smooth results without distortion or health risks.

Recommended Tools

• Wet/dry sandpaper sheets.
• Soft sanding block or mini files for details.
• Respirator or full-face mask rated for fine particulates.
• Nitrile gloves and vacuum with HEPA filter.
• UV lamp (for post-curing resin prints).

Best Grit Sequence for 3D Print Finishing

• 220 grit: initial leveling of layer lines or support marks.
• 400 grit: remove coarse scratches and refine contours.
• 800 grit: smooth transition before primer or polish.
• 2000 grit: final micro-finish for clear coats or translucent parts.

Step-by-Step: Sanding UV-Resin Prints

1. Post-cure fully. Ensure prints have 100 % UV cure—tacky surfaces smear instead of powdering.
2. Wet-sand with 220 grit. Use light pressure and water to trap dust; resin dust is hazardous if inhaled.
3. Progress through 400 → 800 → 2000 grit. Keep surfaces flooded with water; switch sheets often to avoid buildup.
4. Dry and inspect. Hold under raking light to confirm even matte finish with no shiny low spots.
5. Optional clear coat. For glossy miniatures, spray clear acrylic once the surface is fully dry.

Step-by-Step: Sanding FDM Prints

1. Start at 220 grit dry. Knock down layer ridges and support scars gently—avoid staying in one spot.
2. Switch to 400 grit wet. Keeps PLA and PETG cool while removing coarse scratches.
3. Refine to 800 grit. Smooth transitions; small circular motions work best.
4. Finish with 2000 grit (optional). Achieve satin sheen before primer or paint.
5. Wipe clean. Use a damp microfiber; avoid solvents that attack plastics.

Special Cases

ABS prints sand well but release styrene odor—ventilate. For resin miniatures with fragile supports, use micro-files and low-pressure sanding sticks instead of power tools.

Pro Tips

• Always wear PPE—resin dust is toxic and filament dust irritates lungs.
• Wet-sand resin prints; dry-sand FDM plastics only at low speed.
• Between grits, rinse parts to remove trapped abrasive particles.

Aftercare

• Wash resin parts after sanding, then post-cure again under UV for 10 min.
• Prime FDM prints before painting to fill micro-pits.
• Store sanded prints in dust-free boxes until coating.

FAQs

• Can I dry-sand resin? Avoid it—resin dust is hazardous and clogs paper fast.
• Why is my PLA melting? Too much speed or pressure; slow down and switch to wet sanding.
• Does 2000 grit make prints paint-ready? Yes—prime lightly after 2000 for glass-smooth surfaces.

Watch & Learn

For every stage: stock coarse, fine, and super-fine grit packs to tackle everything from print lines to mirror finishes safely.