Typical Accuracy by Process: An Overview
The achievable precision in 3D printing is largely determined by the underlying manufacturing process. The values listed here are typical reference points and may vary depending on the machine type, material, and process parameters.
FDM (Fused Deposition Modeling) / FFF (Fused Filament Fabrication)
Typical accuracy:
±0.2 mm to ±0.5 mm for smaller parts (up to approx. 100 mm); above that, typically around 0.2% of the dimension.
Explanation:
Accracy is strongly influenced by factors such as layer height, nozzle diameter, extrusion temperature, cooling settings, and axis calibration. Larger components are more prone to warping due to thermal stress and uneven cooling. Anisotropy (different properties in the X/Y vs. Z direction) also plays a significant role.
Applications:
Functional prototypes, visual models, tools, jigs, and simple end-use parts.
SLA (Stereolithographie) / DLP (Digital Light Processing)
Typical accuracy:
±0.05 mm to ±0.1 mm for small parts; above that, typically around 0.05% of the dimension.
Explanation:
These technologies use UV light to cure liquid photopolymer resins. Their high precision results from either point-wise (SLA) or area-wise (DLP/LCD) exposure. Influencing factors include optical resolution, resin viscosity, exposure time, and resin shrinkage during curing and post-curing.
Applications:
High-detail prototypes, investment casting molds, dental models, jewelry, medical models, and optical components.
SLS (Selective Laser Sintering)
Typical accuracy:
±0.2 mm to ±0.3 mm for smaller parts; beyond that, typically around 0.2% of the dimension.
Explanation:
In SLS, plastic powder is selectively sintered using a laser. Accuracy depends on laser spot size, layer height, chamber temperature control (to reduce warping), and the material’s shrinkage behavior. As no support structures are needed, errors from support removal are eliminated.
Applications:
Functional prototypes, complex lattice structures, small-series production of load-bearing parts, replacement components.
SLM (Selective Laser Melting) / DMLS (Direct Metal Laser Sintering)
Typical accuracy:
±0.05 mm to ±0.1 mm for small parts; beyond that, typically around 0.1% of the dimension.
Explanation:
These processes fully melt metal powder using high-power lasers. Precision is comparable to SLA/DLP and meets industrial standards. Key factors include laser power, scan speed, powder quality, inert gas atmosphere, and especially the control of thermal stress during melting and cooling. Post-processing such as heat treatment is often required to relieve internal stresses and stabilize dimensions.
Applications:
High-performance components for aerospace, medical implants, automotive parts, and tooling with conformal cooling.
Key Factors Affecting Dimensional Accuracy
Dimensional accuracy in 3D printing is the result of a complex interplay of many variables:
Part geometry and orientation
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Thin walls, overhangs, fine features: Particularly susceptible to warping or deformation due to internal stress and inadequate cooling.
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Part orientation in the build space: Affects the need for support structures, thermal distribution, resulting warping, surface quality, and mechanical anisotropy. Optimized orientation can significantly improve accuracy.
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Hollow or enclosed volumes: May lead to printing errors if pressure compensation is not considered.
Printing parameters
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Layer height: Finer layers increase Z-resolution and often improve dimensional accuracy, but increase print time.
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Infill density and pattern: Affect stiffness and shrinkage behavior of the part.
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Printing temperatures (extruder, build plate, chamber): Poor thermal management can lead to warping, poor layer adhesion, and dimensional deviations.
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Printing speed: Excessive speeds may reduce accuracy, especially with complex geometries.
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Cooling settings: Insufficient or excessive cooling can lead to warping or layer separation.
Material properties
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Shrinkage behavior: All materials shrink when cooling or curing. This shrinkage is material-specific and must be compensated for in the slicer or design.
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Warping tendency: Materials with high thermal expansion and rapid cooling (e.g., ABS, Nylon) are more prone to warping.
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Moisture absorption (hygroscopy): Some polymers (e.g., Nylon) absorb moisture, which can negatively affect print quality and accuracy.
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Post-processing effects: Steps such as curing (resins), sintering (ceramics), heat treatment (metals), or machining may cause further dimensional changes.
Machine and maintenance
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Calibration: Precise calibration of axes, print bed, and extruder (flow rate) is fundamental for accurate results.
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Machine rigidity and build quality: Industrial printers are typically more robust and accurate than desktop machines.
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Nozzle condition (FDM): Worn or clogged nozzles reduce extrusion precision.
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Software and firmware: Modern, well-configured slicing software and printer firmware enhance process control and improve accuracy.
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Environmental conditions: Fluctuations in temperature and humidity can affect print stability and dimensional accuracy.
Strategies for Improving Dimensional Accuracy
To achieve optimal precision in 3D printing, the following strategies are recommended:
Simulation and test prints
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Finite Element Analysis (FEA): Can help predict potential stress concentrations or deformation before printing.
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Test prints: Small, representative test pieces with critical geometries should be used to calibrate parameters and determine material shrinkage.
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Statistical Process Control (SPC): For serial production, monitoring of print parameters and dimensions is crucial to detect deviations early.
Design for Additive Manufacturing (DfAM)
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Fit tolerances: Account for the specific tolerances of the chosen printing process when designing mating parts (e.g., 0.1–0.3 mm clearance).
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Minimizing warping: Avoid large, flat surfaces and uneven wall thicknesses. Consider adding ribs or reinforcing features where appropriate.
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Optimized orientation: Strategic alignment in the build space can reduce the need for supports, improve surface quality, and minimize distortion.
Post-Processing
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Machining: For highest precision, parts may be milled, drilled, or ground after printing—especially for metal components.
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Surface finishing: Sanding, polishing, or chemical smoothing (e.g., vapor smoothing for ABS) can improve surface quality and indirectly dimensional accuracy by removing irregularities.
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Heat treatment: Especially for metal parts, post-print heat treatment (e.g., annealing) is essential to relieve residual stresses and stabilize final dimensions.
Quality control and measurement technology
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Coordinate Measuring Machines (CMM): For high-precision measurements of complex geometries.
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Optical measurement systems / 3D scanners: Enable non-contact dimensional verification against CAD models.
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Gauges and manual tools: Calipers, micrometers, and gauge blocks for simple geometrical checks.
Conclusion: Achieving Precision through Expertise
3D printing can deliver exceptional precision and meet the highest dimensional requirements in industrial applications. However, this requires a deep understanding of each process’s limitations, the material behaviors, and the many influencing factors. Success depends not only on choosing the right technology but also on thoughtful design (DfAM), stable process control, and—if necessary—precise post-processing.
At AM Worx, we support you with in-depth expertise, advanced measurement technology, and years of experience in the dimensional accuracy of additively manufactured parts. We help define the ideal tolerances for your application and ensure your 3D-printed components meet the required precision and functionality.