Dry Sanding for Resin Prints

Make the print safe and stable before finishing

Dry sanding a resin print begins after the material maker’s washing, drying, and post-curing requirements—not while liquid resin or solvent remains on the surface. Formlabs instructs users to let washed prints dry fully before post-curing or post-processing and to follow each resin’s current cure settings. Different resins behave differently, so a schedule for one standard model resin cannot be assumed safe for flexible, castable, biocompatible, engineering, or filled materials.

Read the resin safety data sheet. Wear the specified eye, skin, and respiratory protection, and use appropriate ventilation or source capture. Do not dry sand a sticky, solvent-smelling, or visibly wet print. If the part has a regulated end use or relies on validated mechanical properties, follow its controlled post-processing procedure instead of this cosmetic guide.

Once the print is ready, remove supports by the manufacturer’s method. Eye protection matters because clipped support pieces can fly. Work over a clean tray or bench so small parts and dust remain contained.

Map each support mark before choosing a tool

Treat the model as zones rather than sanding the entire surface.

• Raised nub: Clip or shave most of the high point with an approved tool, leaving a tiny allowance for sanding. Do not lever the support away and tear a crater.
• Shallow witness ring: Sand locally with a small supported piece of abrasive.
• Divot: Sanding cannot fill a low spot. Use a resin-compatible filler or primer system if the finish specification permits it.
• Detail edge or texture: Mask it, work around it, or accept the witness mark. Removing adjacent detail is usually worse than leaving a tiny imperfection.
• Broad flat face: Use a firm block that bridges the high points. Finger pressure alone can dish the center.

For curves and flats, the block-versus-sponge guide helps match support to geometry. On miniature faces, lettering, threads, snap fits, or sealing surfaces, do not sand until you have defined what dimensions and detail must survive.

Choose grit by remaining height

The correct starting grit depends on what remains after trimming. Begin with the finest grade that reduces the mark at a useful rate.

A 320-grit sheet in a 25-sheet format is one cataloged option for localized refinement. A second route to the same 320-grit specification is included for comparison. The listing identifies format, grit, and pack count; it does not establish compatibility with a particular printed resin.

If 180 was necessary, follow with 220, 320, and then 400 as the target finish requires. Change sanding direction at each grit so surviving coarse lines remain visible. A paint primer may reveal scratches that were hard to see in bare translucent resin, but the primer maker should define its own surface preparation.

Sand the scar, not the whole model

Cut small abrasive pieces and label the grit on the clean backing. Wrap a firm sliver for a flat ledge, use a narrow folded edge for access, or attach paper to a shaped tool that matches the intended curve. Keep the working face on the defect and keep sharp folded corners away from nearby detail.

Use light strokes, then stop after a few seconds to brush or capture dust and inspect under raking light. Rotate the model rather than twisting your wrist into an unstable angle. If the part warms, the debris smears, the abrasive loads immediately, or the surface becomes rubbery, stop. Recheck drying, cure, resin-specific behavior, and dust control.

Do not use more pressure when a small piece of paper stops cutting. Replace it. If you are finishing a batch, record how many similar support marks one piece handles before cut quality drops; the abrasive cut-life log offers a simple measurement approach. That is more useful than saving a glazed piece until it gouges unpredictably.

Between grits, remove dust with a method approved for the resin and downstream finish. Keep coarse debris out of recesses. Avoid unapproved solvents, oils, or coatings; they may interfere with paint, bonding, biocompatibility, or appearance.

Put the 3D-print grit clip in context

Inspect at three scales

Check the repair in three ways before declaring it finished:

1. Macro: Under low-angle light, the original raised mark is gone and no coarse scratch crosses into untouched detail.
2. Shape: A straightedge, profile gauge, or fingertip used lightly shows no flat spot or hollow where a curve should continue.
3. Function: Holes, mating faces, threads, hinges, lettering, and thin walls retain the dimensions and edges they need.

Do not chase a low divot by widening it. Do not erase layer texture from the whole model just to disguise one witness ring. For a clear or translucent display part, dry sanding alone leaves a matte pattern; follow the resin maker’s wet-refinement or coating process if transparency is the actual goal.

The efficient workflow is local and evidence-led: complete resin-specific post-processing, classify each mark, remove a raised nub before sanding, start with the finest effective grit, inspect every few strokes, and protect detail. The smallest successful repair is usually the one that leaves the model most faithful to its design.