Introduction
One of the most common questions from new prop makers is: how do I get rid of those layer lines? Sanding is the answer — and done properly, it can turn a standard FDM print into something that looks injection-moulded.
This guide walks you through the complete sanding process for 3D printed PLA+ props, from the first coarse cut to a mirror finish. Whether you want a surface ready for painting or a polished display piece, this guide has you covered.
What You'll Need
- Sandpaper in multiple grits: 120, 220, 400, 600, 800, 1000, 1500, 2000 (and optionally 3000+ for polishing).
- A sanding block or backing pad — sanding freehand creates uneven pressure and rounding of sharp edges.
- Water (for wet sanding in the higher grits).
- Primer spray — essential for revealing imperfections between sanding stages.
- Optional: filler primer for heavy layer line coverage, polishing compound for a gloss finish.
Stage 1: Coarse Sanding (120–220 Grit)
Start with 120 or 220 grit to remove the worst of the layer lines. Work with even, consistent strokes — don't press too hard or you'll sand unevenly and create flat spots.
Focus on the largest, most visible surfaces first. On curved surfaces, use a flexible sanding sheet or wrap the paper around a foam block to maintain the curve.
This stage is about removing material, not achieving smoothness. The surface will look scratched — that's fine.
Stage 2: Primer and Inspection
After 220 grit, apply a thin coat of grey spray primer. This is a critical step that many beginners skip — and they always regret it.
Primer reveals every remaining layer line, scratch, and imperfection with brutal clarity. Under raking light, you'll see exactly where more work is needed. Mark these areas and sand them back before continuing.
This primer-sand-prime cycle is how professional model makers achieve flawless surfaces.
Stage 3: Medium Sanding (400–800 Grit)
Working through 400, 600, then 800 grit progressively removes the scratches left by coarser paper. Each stage should remove the scratch marks from the previous one.
At 600 grit, switch to wet sanding — dip the paper in water, or keep the surface wet with a damp cloth. Wet sanding lubricates the process, reduces clogging, and produces a significantly smoother result.
Stage 4: Fine Sanding (1000–2000 Grit)
Continuing wet sanding through 1000, 1500, and 2000 grit progressively refines the surface. By 2000 grit, your surface should feel glass-smooth to the touch.
Apply another thin coat of primer after 1000 grit to check your progress. Any remaining imperfections will be obvious at this stage and much easier to address than they would be at the final finish stage.
Stage 5: Polishing (Optional)
For a truly mirror finish — ideal for helmets, armour, or metallic effect props — continue through 2500–3000 grit, then finish with plastic polishing compound applied with a soft cloth.
Alternatively, apply a gloss varnish at this stage, which will produce a similarly reflective result without the polishing work. If you're going to paint the prop, stop at 2000 grit and prime — a mirror finish isn't necessary under paint.
What's Next?
Once your surface is smooth and primed, you're ready to paint. See our Best Paint for 3D Printed Props guide for a full breakdown of acrylic, spray, and enamel options — and our Prop Weathering Techniques guide to take your finish to the next level.
Final Thoughts
Sanding is patient work — but the results are extraordinary. A 3D print that's been properly sanded and primed can genuinely fool people into thinking it was manufactured.
Start with good-quality prints, and the sanding process is much faster. All 3DCre8Design prop kits are printed to a high standard in quality PLA+, giving you the best possible starting point.
Browse our full prop kit range at Best Sellers or check out our New Arrivals — made to order, shipped from the UK.