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3D Print Finishing Guide: Sanding, Priming and Painting

By Dynafabs

3D print finishing guide: remove supports, sand away layer lines, prime and paint PLA, ABS, ASA and resin parts, plus how to order prints that finish well.

What a 3D print looks like straight off the printer

Every 3D print leaves the machine with a few tell-tale signs of how it was made. On FDM (filament) prints you'll see fine horizontal layer lines, a slightly different texture on the surface that sat on the build plate, and small marks where supports touched the part. Resin prints are much smoother, but they can carry tiny support nubs and need a final clean and cure.

For lots of jobs that raw finish is exactly what you want: brackets, jigs, enclosures and prototypes often go straight into use. But if your part is a display piece, a prop, a product sample or a miniature you plan to paint, a little post-processing makes a huge difference. This guide walks through the main finishing options, which materials suit them, and how to order a print from Dynafabs that's easy to finish.

Start with the right settings

The smoothest finish starts before the part is printed. Three choices matter most:

• Layer height. Finer layers mean smaller steps on curved and sloped surfaces, so there's less sanding to do. Our layer height, infill and walls guide explains the trade-off between detail and print time.
• Orientation. The face you care about most should point away from supports. Surfaces facing up or standing vertical usually look best. See our print orientation guide for examples.
• Walls. If you plan to sand hard, ask for extra walls so you don't sand through to the infill underneath.

When you request a quote, just tell us which side is the "show" face and that you plan to sand or paint it. We can then set the part up with that in mind.

Removing supports cleanly

Supports are the temporary scaffolding that hold up overhangs while printing. On FDM parts they usually snap or peel away, leaving a slightly rough patch. A sharp hobby knife, flush cutters and a little sanding tidy this up.

Work slowly, cut away from your hands, and wear eye protection when snapping brittle supports. On resin prints, clip supports off with flush cutters rather than twisting them, which can pull chunks out of the surface.

Sanding: the workhorse of finishing

Sanding is the single most useful finishing step. A simple routine works for most FDM parts:

1. Start with a coarse grit to knock down layer lines and support marks. 2. Move progressively through finer grits, never skipping too far between them. 3. Finish with wet sanding using waterproof paper for a smooth, matt surface.

Keep the paper moving and avoid pressing hard in one spot, especially on PLA, which can soften from friction heat. Sanding sponges and files are handy for curves and tight corners.

How the materials compare:

• PLA sands reasonably well if you go gently and keep it cool.
• PETG is tougher and slightly gummy, so it takes more patience to sand smooth.
• ABS and ASA sand nicely and are the usual choice when a part needs heavy finishing.
• TPU is flexible and doesn't really sand; leave it as printed.
• Resin sands to a very fine finish but the dust must be handled carefully (see the safety section below).

Not sure which suits your project? Our material comparison guide and materials page cover strengths, heat resistance and finish.

Filler primer for a glassy surface

If sanding alone doesn't hide the layer lines, a filler primer (sometimes called high-build primer) is the next step. It lays down a thicker coat that fills tiny grooves. Spray a light coat, let it dry fully, sand it back with fine paper, then repeat until the surface is even.

For small gaps or seams between glued parts, a modelling putty or two-part filler does the job before priming.

Painting your print

Once primed, most 3D prints take acrylic and spray paints well. Thin coats beat thick ones: they keep detail crisp and dry faster. Finish with a clear varnish if the part will be handled a lot or used outdoors.

Miniatures are a special case. Fine detail is easy to drown in paint, so many people prefer to hand them to a professional. Dynafabs collaborates with Some Miniatures, a miniature painting business, and our tips for painting 3D printed miniatures cover prep in more detail.

Other finishing options

• Gluing and assembly. Large models are often printed in sections. Plan joints in hidden places and use a glue suited to the material.
• Heat-set inserts. For parts that need strong, reusable screw threads, see our heat-set inserts guide.
• Chemical smoothing. ABS can be smoothed with solvent vapour, but the chemicals involved are hazardous and need proper ventilation and safety kit. It's not something to try casually at the kitchen table.

Stay safe while finishing

Wear a dust mask when sanding, ideally wet sanding to keep dust down. Uncured or partly cured resin can irritate skin, so wear nitrile gloves when handling resin prints and dust. Use spray paints and primers outdoors or in a well-ventilated space, and always follow the instructions on the product label.

FAQ

Can I order a print that needs no finishing? Often, yes. Choosing a fine layer height, a smart orientation or resin for small detailed parts can give a finish that's good enough to use straight away.

Which material is easiest to sand and paint? ABS and ASA are popular for heavy finishing, and PLA is fine with a gentle touch. TPU isn't suited to sanding.

Will sanding weaken my part? Light sanding removes very little material. If you plan to sand aggressively, ask for extra walls so the strength stays where it should.

Do you have more questions answered? Our FAQ page covers ordering, files and delivery.

Ready to print something worth finishing?

Whether it's a prop, a product sample or a part you want to paint, tell us how you plan to finish it and we'll set it up to make your life easier. Get your Dynafabs quote and let us know which face matters most.

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