Post-Processing FDM Prints — Sanding, Priming, and Painting

Post-Processing FDM Prints — Sanding, Priming, and Painting Off the printer, FDM parts have visible layer lines. Here's how to get a smooth, painted finish worthy of a display or product. Sanding Work through grits progressively — don't skip steps. Tips: Wet sand from 400 grit up — less dust, better finish PLA sands easier than PETG Don't over-sand thin walls — can cut through Use a sanding block for flat surfaces to avoid rounding edges Filling For deep layer lines or imperfections, fill before priming: Spot putty / body filler — works well, sand smooth when dry XTC-3D epoxy coating — brush on, self-levels, adds strength Polyester primer (high-build) — multiple coats fill shallow lines Priming 1. Clean part with IPA — remove all oils and dust 2. Apply filler primer in light coats (2–3) 3. Let dry fully (30 min between coats) 4. Sand with 800 grit wet 5. Inspect — re-prime any remaining lines 6. Final 1000–1500 grit before paint Painting Rattle cans work fine for most hobby use Adhesion promoter first for PETG/ABS — paint flakes off otherwise Light thin coats — 2–3 coats minimum Let cure 24 hours before handling Clear Coat Matte, satin, or gloss to taste 2K rattle can (2-component) for durability Wax after full cure for protection

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