3D Printing Tolerances: What Accuracy Can You Actually Expect?
Dimensional accuracy varies dramatically between 3D printing technologies, from ±0.05mm with SLA to ±0.5mm with FDM. Understanding these tolerances prevents costly surprises and helps you choose the right technology.
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Tolerance Overview
SLA/DLP: ±0.05-0.15mm. Best dimensional accuracy for polymers. SLS: ±0.1-0.3mm. Good accuracy with slight warping on large flat surfaces. MJF: ±0.1-0.3mm. Similar to SLS, excellent consistency across build volume. FDM: ±0.2-0.5mm. Depends heavily on printer calibration and material. DMLS/SLM: ±0.05-0.2mm. High accuracy for metal, but requires stress relief.
Factors That Affect Accuracy
Part size matters: tolerances are typically ±0.1mm + 0.1% of dimension length. Orientation in the build affects Z-axis vs XY accuracy. Post-processing (sintering, heat treatment) can cause shrinkage. Wall thickness below 1mm is challenging for all technologies. Holes and pins may need post-machining for tight fits.
Technologies compared: SLA, SLS, Multi Jet Fusion, FDM, DMLS.
Practical Advice
For press fits and tight tolerances, always discuss with your supplier upfront. Most will recommend post-machining critical surfaces. Design with tolerance bands in mind: if you need ±0.05mm, you need SLA or post-machined metal AM.
Frequently asked questions
Which 3D printing technology has the best tolerances?
SLA and DLP offer the best dimensional accuracy for polymer parts (±0.05mm). For metal, DMLS/SLM achieves ±0.05-0.1mm on small features.
Can 3D printed parts achieve injection molding tolerances?
Standard injection molding achieves ±0.05-0.1mm. SLA can match this for small parts. For most AM technologies, you'll need post-machining on critical surfaces to achieve injection molding-level tolerances.
How do I specify tolerances for 3D printing?
Use GD&T (Geometric Dimensioning and Tolerancing) on your drawings. Call out critical dimensions explicitly. Discuss with suppliers which surfaces need tight control: they can orient parts and add machining stock accordingly.