What grit sandpaper should I start with?

Start with 120-grit to remove layer lines quickly, then work through 220, 400, and 600 grit for a smooth finish. For a glossy finish, continue to 1000 or even 2000 grit. Wet sanding from 400 grit onward gives the best results.

Do I need to prime before painting?

Yes, priming is strongly recommended. Filler primer fills remaining layer lines and creates a uniform base for paint adhesion. Apply 2-3 light coats, sanding between each with 400-600 grit. Automotive filler primer works well.

Can I sand PETG and flexible materials?

PETG is harder to sand than PLA as it tends to gum up sandpaper. Use wet sanding and lower grits. TPU cannot be sanded effectively due to its flexibility. For PETG, consider chemical smoothing with ethyl acetate instead.

How do I get a perfectly smooth finish?

Print at 0.1mm layers, sand through grits 120-1000, apply 2-3 coats of filler primer (sanding between), then paint with 2-3 coats. For PLA, you can also use XTC-3D epoxy coating which fills lines and self-levels.

3DPrintCalcs

Post-Processing Calculator — Sanding, Priming & Painting Time

Estimate time and materials for sanding, priming and painting printed parts.

Surface Area

From slicer or estimate

Layer Height

Finish Level

Material

Your Labour Rate

How We Calculate This

Post-Processing Time Estimation

Sanding time = Surface area x Finish factor x Layer factor x Material factor
Priming time = Surface area x Priming factor
Painting time = Surface area x Painting factor
Total cost = Total active time x Labour rate

Thicker layer heights require more sanding to remove layer lines. The finish level determines how many sanding passes and coating steps are needed. Drying time between coats is additional.

Frequently Asked Questions

Related Calculators

PLA vs PETG Calculator

Compare PLA and PETG properties side by side for your specific use case.

Material Strength Calculator

Estimate tensile and compressive strength based on material and print orientation.

Heat Resistance Calculator

Check if your printed part will withstand a given operating temperature.

Flexibility Calculator

Calculate shore hardness and flex properties for TPU and flexible filaments.

Material Weight Calculator

Calculate the weight of a printed part from its volume and material density.

Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.