Mastering 3D Printing Tolerances: Ensuring Precision Across Technologies
In additive manufacturing, tolerances define the acceptable variation between a design and its printed reality. For engineers and procurement professionals, understanding these deviations is critical, especially when parts must fit together, perform under load, or meet industry specifications.
Understanding Tolerance vs. Accuracy vs. Precision
- Tolerance is the allowable deviation from the intended dimension—a design parameter you set.
- Accuracy measures how closely your printed part aligns with the design.
- Precision refers to consistency, how repeatably similar multiple prints are to each other.
Expected Tolerances by Technology
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Different 3D printing methods deliver varying levels of dimensional control. Here are typical ranges across popular technologies:
| Technology | Typical Tolerance | Notes |
|---|---|---|
| SLA / DLP | ± 0.1 mm or ± 0.2% | High-detail resin prints |
| SLS / MJF | ± 0.3 mm or ± 0.3% | Durable, complex geometries |
| FDM | ± 0.5 mm or ± 0.5% | Least precise; budget-friendly |
| Carbon DLS | ± 0.1 mm or ± 0.1% | Ultra-precise polymer parts |
| DMLS (Metal) | ± 0.1–0.2 mm or ± 0.2% | High accuracy metal printing |
| PolyJet | ± 0.05–0.1 mm + 0.05 mm per mm | Ideal for ultra-fine features |
Key Design Tips for Tolerance Control
Overprint small features: Compensate for accuracy loss during the digital design phase.
Adjust fit clearances based on the required fit type:
Tight Fit: ~0.13 mm clearance
Normal Fit: ~0.25 mm
Loose Fit: ~0.5 mm
Account for part size: A ± 0.3% tolerance on large parts can mean millimeters of deviation.
Plan for post-processing impact: Sanding or coating can both reduce and increase dimensions. For metal 3D prints, it’s common to print with a slight oversize (+1–2 mm) for later CNC finishing.
Why It Matters for Your Teams
- Engineers can ensure parts fit and perform as intended by designing with realistic tolerances, avoiding costly trial-and-error.
- Procurement teams benefit by anticipating manufacturing variability, making better decisions on part quantities, suppliers, and acceptable risk thresholds.
Tolerances in 3D printing are not fixed; they fluctuate based on material, process, and size. By designing with realistic expectations and allowances, you bridge the gap between CAD and reality, enabling parts that fit, function, and repeat reliably.
