How Accurate is SLA 3D Printing? A Technical Look at Tolerances
SLA 3D Printing Accuracy: Understanding Tolerance Limits
SLA (stereolithography) delivers outstanding precision and surface quality, making it ideal for applications that require fine details and tight dimensional control—think dental parts, intricate prototypes, and small-production components. To evaluate SLA for your project, it’s important to grasp its typical accuracy range, what impacts it, and how it compares to other 3D printing methods.
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Standard SLA Tolerances: What to Expect
- Typical dimensional accuracy spans from ± 0.05 mm to ± 0.15 mm.
- Parts under 100 mm often achieve around ± 0.05 mm, especially when printed on calibrated industrial machines in controlled environments.
For precision features like alignment holes or press fits, placing them in the XY plane tends to yield the most reliable results.
📋 Feature Tolerance Cheat Sheet
| Feature Type | Minimum Size | Expected Accuracy | Notes |
|---|---|---|---|
| Wall thickness | ~0.5 mm | ± 0.1 mm | Increase thickness if under load |
| Holes/slots | ≥ 0.3 mm diameter | ± 0.05–0.1 mm | Holes often print undersized |
| Bosses & pegs | ≥ 0.5 mm diameter | ± 0.05–0.1 mm | Leave ~0.1 mm clearance |
| Text/engraving | ≥ 0.2 mm stroke width | ± 0.05 mm | Fine serif fonts may not render clean |
| Snap-fit / enclosures | ≥ 0.8 mm feature | ± 0.1 mm | Account for cure-related shrinkage |
Design Tips for SLA Accuracy
- Provide appropriate clearance (0.1–0.15 mm) for assembly features to compensate for resin shrinkage.
- Avoid over-constraining mating geometries—embed small chamfers or reliefs to accommodate minor part variability.
- Anchor thin features: ribs or fins under ~1 mm should have a generous base or be printed perpendicular to the platform to prevent distortion.
- Control overcuring: small cavities or logos can be affected by light bleed. Low-viscosity resins can help, and assume slight positive deviations for internal features.
SLA vs Other 3D Printing Methods
SLA offers smoother surfaces and tighter tolerances than many alternatives:
| Technology | Tolerance Range | Surface Finish | Best Suited For |
|---|---|---|---|
| SLA | ± 0.05–0.15 mm | Smooth, glossy | Medical, precision parts, tooling |
| FDM | ± 0.2–0.5 mm | Layered | Basic prototypes, fixtures |
| SLS (Nylon) | ± 0.2 mm | Slightly grainy | Functional components, brackets |
| MJF | ± 0.2 mm | Grey, uniform finish | PA12 enclosures, production parts |
| DLP | ± 0.05 mm | Very detailed | Miniatures, dental, small features |
Key Factors Affecting SLA Accuracy
- Printer calibration & optics: Precise laser alignment and a clear resin tank are essential. Misalignment or tank distortion can shift dimensions.
- Resin chemistry & shrinkage: Shrinkage typically ranges from 1.5–3%. Filled rigid resins reduce shrinkage but can be more brittle.
- Mechanical stresses during printing: Peel and layer forces may distort tall or asymmetric geometry. Slower peel rates and sturdy supports help. For parts over ~150 mm, break into sections to preserve XY fidelity.
- Post-processing variability: UV curing duration and intensity significantly influence final size. Stick to consistent, resin-specific cure cycles. Over-curing can warp fine features.
Resin Types & Relative Dimensional Stability
- Standard resin: Moderate stability, good for visual or concept prototypes.
- Rigid (glass‑filled) resin: Low shrinkage, ideal for rigid enclosures and connectors.
- Flexible resin: Less accurate, high expansion—better suited for seals or grips.
- Dental & biocompatible resins: Precision-engineered with verified shrinkage; excellent for medical uses.
- High‑temperature resin: Stable under heat, though thin features may warp.
Industrial Use Case
A UK designer printed a wearable medical clip with a rigid grey resin on a Form 3B printer. By orienting the part horizontally and maintaining consistent post-cure timing, the enclosure aligned within ± 0.06 mm, enabling rapid iteration and assembly-ready parts within a week—an improvement over CNC turnaround time.
When Is SLA “Accurate Enough”?
- For tolerances tighter than ± 0.05 mm, CNC machining remains more precise.
- But SLA shines in speed, cost‑efficiency, and complex geometries—especially in low‑volume runs or prototype iterations.
- A hybrid approach—print near-net-shape in SLA and finish with CNC—balances speed, complexity, and accuracy. Example: SLA housings post-reamed to ± 0.02 mm positional accuracy.
Dimensional Inspection & Batch Control
- Validate key dimensions using calipers, laser scanning, or CMM.
- Measure multiple spots on critical features, both before and after curing.
- Follow resin-specific accuracy guides (e.g. manufacturer datasheets or whitepapers).
- Log build details—orientation, resin batch, cure time—for consistent results across runs.
Frequently Asked Questions (FAQ)
Can SLA parts reliably achieve under ± 0.05 mm tolerance?
‑ While small localized features may reach this, it isn't reliable for whole parts unless under ~50 mm size.
How does ambient humidity or temperature affect results?
‑ SLA resins are sensitive to UV exposure and moisture—store materials in a dry, temperature-controlled environment to maintain dimensional stability.
Are desktop SLA systems comparable to industrial ones?
‑ Industrial systems offer more consistent accuracy thanks to better optics and environmental control. Desktop printers can achieve similar results with strict calibration and maintenance.
How frequently should SLA printers be recalibrated?
‑ Every 15–20 prints, or whenever resin or print profile changes, to ensure dimensional fidelity.
Bottom Line
SLA enables exceptional dimensional accuracy—± 0.05 to ± 0.15 mm—making it highly effective for products with tight geometries, surface detail, or small assemblies. By understanding resin behavior, print orientation, curing effects, and design-for-manufacturability principles, you can consistently achieve production-grade tolerances. For sub-0.05 mm needs, consider hybrid workflows combining SLA with precision machining.
Need help designing to SLA tolerances or choosing a resin? Just ask!