Engineering Guide
FDM Print Tolerances — Engineering Guide
Understanding FDM tolerances helps you design parts that print correctly the first time. This guide covers standard achievable tolerances, design recommendations for fits and holes, and what to expect from production FDM parts at Spline Arc.
Standard FDM Tolerances at Spline Arc
| Feature | Standard Tolerance | Notes |
|---|---|---|
| Dimensional accuracy | ±0.2mm on most features | Larger parts may see ±0.3 to 0.5mm |
| Layer height | 0.1 to 0.3mm | Finer layers improve surface finish, increase print time |
| Minimum wall thickness | 1.2mm recommended | Thinner walls possible but reduce strength |
| Minimum hole diameter | 2.0mm | Smaller holes require post-drill for accuracy |
| Hole diameter (as printed) | Undersize by 0.1 to 0.2mm | Design holes 0.2mm oversized or post-drill |
Fit Recommendations
Clearance fit (moving parts)
Add 0.3 to 0.5mm clearance per side. FDM parts expand slightly in high humidity materials like Nylon.
Press fit
Design 0.1 to 0.2mm interference. Test on a single part before committing to a full run.
Heat set inserts
Leave a boss diameter equal to the insert OD minus 0.4mm. We install inserts as part of our standard finishing.
When to Call Us Before Printing
If your part has features tighter than ±0.2mm, thin walls under 1.5mm, or holes under 3mm that need to be accurate without post-drilling, contact us before submitting. We review every file for manufacturability and flag issues before the job starts — not after.
Free DFM review on every quote. No minimum order.
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