TOLERANCES & PRECISION
Technical guide to dimensional precision for FDM and SLA 3D printing
3d.dglabs.cloudWhat are tolerances in 3D printing?
Tolerance is the maximum allowable dimensional variation between a CAD-designed part and the physical printed part. In 3D printing this variation depends on the technology, material, part orientation and process parameters. Understanding real tolerances is essential to design parts that fit correctly, meet the intended mechanical specifications and fulfil the functional requirements of the project.
FDM Tolerances
Fused Deposition Modelling — standard precision ±0.2–0.3 mm
FDM printing extrudes molten thermoplastic filament layer by layer. XY-plane precision depends mainly on nozzle diameter and print profile; Z-axis precision depends on the selected layer height.
Dimensional precision
| Parameter | Value | Notes |
|---|---|---|
| Standard XY precision | ±0.2–0.3 mm | Standard print profile |
| Optimal XY precision | ±0.15–0.2 mm | Fine profile, longer print time |
| Z precision | ±0.1–0.2 mm | Depends on layer height |
| Available layer heights | 0.1 / 0.15 / 0.2 / 0.3 mm | Default: 0.2 mm |
Recommended minimum dimensions
| Feature | Recommended minimum | Absolute minimum |
|---|---|---|
| Wall thickness | 1.2 mm | 0.8 mm |
| Hole diameter | 2.5 mm | 1.5 mm |
| Pin / cylinder | 2.0 mm diameter | 1.0 mm |
| Embossed detail | 0.8 mm wide × 0.8 mm deep | 0.5 mm × 0.5 mm |
SLA Tolerances
Stereolithography — standard precision ±0.05–0.1 mm
SLA printing photopolymerises liquid resin with a high-precision UV laser. Because it does not rely on mechanical extrusion, it produces smoother surfaces and significantly better dimensional tolerances than FDM.
Dimensional precision
| Parameter | Value | Notes |
|---|---|---|
| Standard XY precision | ±0.05–0.1 mm | Laser spot resolution: ~140 µm |
| Optimal XY precision | ±0.025–0.05 mm | With fine calibration |
| Z precision | ±0.05–0.1 mm | Depends on layer height |
| Available layer heights | 0.025 / 0.05 / 0.1 mm | Default: 0.05 mm |
Recommended minimum dimensions
| Feature | Recommended minimum | Absolute minimum |
|---|---|---|
| Wall thickness | 1.0 mm | 0.5 mm |
| Hole diameter | 1.0 mm | 0.5 mm |
| Pin / cylinder | 1.0 mm diameter | 0.5 mm |
| Embossed detail | 0.4 mm wide × 0.3 mm deep | 0.2 mm × 0.2 mm |
Mechanical fit guide
When designing parts that must fit together (shafts, pins, lids, guides), it is necessary to add a clearance to compensate for printing tolerances. The total clearance shown is distributed symmetrically between the two mating parts.
| Fit type | FDM (total clearance) | SLA (total clearance) | Typical application |
|---|---|---|---|
| Press fit | 0.0–0.1 mm | 0.0–0.05 mm | Permanent inserts, gears, fixed couplings |
| Sliding fit | 0.3–0.5 mm | 0.15–0.25 mm | Lids, drawers, linear guides, hand-assembled parts |
| Loose fit | 0.6–1.0 mm | 0.3–0.5 mm | Housings, enclosures, non-structural accessories |
Important considerations
- The tolerances shown are typical values under standard conditions. Large parts (> 150 mm) or materials with high shrinkage (ABS, ASA) may exhibit greater dimensional variation.
- Part orientation on the build platform directly affects precision and surface finish. We always consult the optimal orientation before production.
- Post-processing (sanding, painting, sealing or plating) changes final dimensions. If the fit is critical, allow an additional 0.1–0.3 mm margin for finishing operations.
- For critical tolerances (< ±0.1 mm), we recommend SLA technology and, if necessary, subsequent machining of functional surfaces.
Questions about your part design?
We analyse your model and advise you on the best technology, print orientation and clearances to ensure the correct fit.