Design and tolerances
What tolerances can 3D printing achieve?
3D printing typically holds ±0.3% to ±0.5% of a dimension, with a minimum that depends on the process. On our service, FDM holds ±0.5% (minimum ±0.3 mm), SLA ±0.5% (minimum ±0.1 mm) and SLS ±0.3% (minimum ±0.3 mm). For anything tighter than about ±0.1 mm, print with an allowance and machine or ream the critical feature.
Reviewed by HenleyPrint3D engineers3 min readUpdated
Key takeaways
- FDM ±0.5% (min ±0.3 mm), SLA ±0.5% (min ±0.1 mm), SLS ±0.3% (min ±0.3 mm).
- Percentage tolerances scale with size: 200 mm varies more than 20 mm.
- Design fits with clearances, not nominal sizes.
- Reserve ±0.05 mm for features you will machine after printing; elsewhere, use the process tolerance.
Suits
Engineers specifying fits, bores and mating faces on printed parts.
Worth knowing
As printed, plan on about ±0.1 mm at best. Finish anything tighter by reaming or machining.
3D printing tolerances by process
| Process | Tolerance | Main error sources |
|---|---|---|
| FDM | ±0.5% (min ±0.3 mm) | Shrinkage, warp, bead width |
| SLA | ±0.5% (min ±0.1 mm) | Post-cure shrinkage, support marks |
| SLS | ±0.3% (min ±0.3 mm) | Cooling shrinkage, powder condition |
| PolyJet | Confirmed per job | Support surfaces |
Clearances for moving, sliding and press fits
| Fit | FDM | SLA | SLS |
|---|---|---|---|
| Free-running (moving parts) | 0.4 to 0.6 mm | 0.3 to 0.5 mm | 0.3 to 0.5 mm |
| Sliding / close fit | 0.2 to 0.4 mm | 0.15 to 0.3 mm | 0.2 to 0.4 mm |
| Press fit | Machine instead | Prototype only | Prototype only |
These clearances are starting points. Material, orientation and wall thickness all shift the result.
How to achieve tighter tolerances
- Ream or drill holes to size, typically about ±0.05 mm.
- Machine bearing seats and mating faces on the printed blank.
- Split large parts into sections and bond them. Each section holds its tolerance better than one large print.
- Reduce warp on large FDM parts with radii on sharp corners and a brim or raft on the base edge.
- Fit threaded inserts instead of printing threads.
Which approach for which tolerance?
| Your requirement | Approach |
|---|---|
| ±0.3 to ±0.5% of size | Print to the quoted tolerance |
| About ±0.1 mm on a small part | SLA, which has the lowest minimum (±0.1 mm) |
| Moving parts | Design clearances of 0.3 to 0.6 mm |
| About ±0.05 mm | Print with allowance, then ream or machine the feature |
| Press fit | Machine the seat on the printed blank |
For hole allowances and other feature rules, see how to design parts for 3D printing and why 3D printed holes come out undersized. For how we measure and record parts, see quality control and inspection.
Frequently asked questions
What is the typical tolerance of 3D printing?
About ±0.1 to ±0.5 mm, or ±0.3 to ±0.5% of the dimension, depending on process, material and part size. Our services quote ±0.5% (FDM and SLA) and ±0.3% (SLS) with minimums stated by process.
Can 3D printing hold ±0.05 mm?
Not as printed. Print the part with a machining allowance, then ream, mill or turn the critical feature; ±0.05 mm is achievable on that feature.
Why are 3D-printed holes too small?
Holes print slightly undersize because of material shrinkage and bead or laser spot geometry. Add 0.2 to 0.4 mm (FDM), 0.1 to 0.3 mm (SLS) or 0.1 to 0.2 mm (SLA) to hole diameters, or ream the hole after printing.
Does part size affect tolerance?
Yes. Percentage tolerances scale with size, so larger parts vary more in absolute terms. Large parts can also warp, which adds to the error.
How do I check a 3D-printed part is in tolerance?
Use callipers or micrometers for simple features, and a CMM or 3D scanner for complex geometry. Agree the inspection method and critical dimensions with your supplier at quote stage.
Which process has the tightest standard tolerance?
SLA, at ±0.5% with a minimum of ±0.1 mm. SLS is ±0.3% with a minimum of ±0.3 mm, and FDM is ±0.5% with a minimum of ±0.3 mm.
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