Finishing and post-processing
What post-processing do 3D-printed parts need?
Every 3D printed part needs a clean-up step set by its process: support removal for FDM and PolyJet, washing and UV post-curing for SLA, and depowdering for SLS. Optional finishes such as sanding, blasting, dyeing, painting, threaded inserts and machining improve appearance or function, but each adds cost and can change dimensions slightly.
Reviewed by HenleyPrint3D engineers3 min readUpdated
Key takeaways
- Mandatory steps depend on process: supports, wash and cure, depowder.
- Sanding, painting and blasting change dimensions slightly.
- Tell us which features are tolerance-critical so we finish them last.
- Fit threaded inserts for repeated screwing.
Suits
Engineers planning surface quality, appearance or assembly features on printed parts.
Worth knowing
Sanding, painting and blasting each change dimensions slightly, so finish tolerance-critical features last.
Required post-processing by process
| Process | Required steps |
|---|---|
| FDM | Remove supports; trim blemishes |
| SLA | Wash in solvent; remove supports; UV post-cure |
| SLS | Depowder; blast to clean |
| PolyJet | Remove support material (waterjet or dissolve) |
Optional finishes and their effects
| Finish | Effect | Dimension change |
|---|---|---|
| Hand sanding | Removes layer lines and support marks | About 0.05 to 0.2 mm if repeated |
| Sand or bead blasting | Uniform matt texture | A few hundredths of a mm |
| Vapour smoothing | Gloss on ABS and ASA | Rounds details, may shrink slightly |
| Priming and painting | Colour, hides layers | Adds about 0.03 to 0.1 mm |
| Dyeing | Uniform colour, usually black on SLS nylon | Negligible |
Which finish for which purpose?
| Purpose | Finish |
|---|---|
| Internal, function only | As-printed or blasted |
| Handled, consistent feel | Blasted or dyed (SLS) |
| Cosmetic prototype | Sanded, primed, painted |
| Repeated screw assembly | Threaded inserts |
| Tight-tolerance interface | Machine or ream the feature |
| Outdoor | ASA or a coating |
Typical dimension change by finish
| Finish | Typical dimension change |
|---|---|
| Hand sanding | About 0.05 to 0.2 mm if repeated |
| Sand or bead blasting | A few hundredths of a mm |
| Priming and painting | Adds about 0.03 to 0.1 mm |
| Dyeing (SLS nylon) | Negligible |
Cosmetic work is normally the largest cost after the print itself. A form-fit model needs none of it, while a part that goes on show needs sanding, priming and paint. Tell us which applies and the quote will reflect it. The full range is on our 3D print finishing services page.
Frequently asked questions
What is post-processing in 3D printing?
Everything done after printing to make a part usable: removing supports or powder, washing and curing resin, and optional steps such as sanding, blasting, dyeing, painting, fitting inserts and machining.
How do you smooth 3D-printed parts?
Sanding, blasting or tumbling smooth most parts; vapour smoothing suits ABS and ASA; priming and painting hide layers. SLA and PolyJet start smoother, so need less work.
Do 3D-printed parts need to be cured?
SLA parts do: after washing they are UV post-cured to finish polymerisation and set properties. FDM and SLS parts go straight to finishing, and some materials benefit from annealing.
Does finishing change part dimensions?
Yes, slightly. Sanding removes material, and paint or coatings add thickness. Tolerance-critical features should be flagged so they are finished or machined last.
Can 3D-printed parts have threads?
Printed threads are weak. For durable, repeatable threads, use heat-set or pressed threaded inserts, or tap holes in thick walls of tough material.
Get started
Talk to an engineer about your part.
Send us your CAD or describe the problem. We recommend the process, material and finish, and quote with the lead time up front.
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