Design Guidelines for Selective Laser Sintering (SLS) 3D Printing
Selective Laser Sintering (SLS) offers exceptional design freedom—complex geometries, internal features, and interlocking parts can be created without support structures thanks to the surrounding unfused powder. However, achieving accurate, reliable, and repeatable results requires thoughtful Design for Manufacturing (DFM). Key creative constraints—like wall thickness, feature detail, and orientation—play a major role in print quality and structural integrity across various industries, including aerospace and healthcare.
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Critical Design Parameters
1. Wall Thickness & Feature Size
Why It Matters: Thin walls may collapse during printing, succumb to warping, or break during depowdering or post-processing.
Guidelines (Nylon PA12 GF):
- Supported walls (connected on two or more sides): minimum 1.5 mm
- Free-standing or load-bearing walls: 2.0–2.5 mm
- Delicate features (e.g., pins/clips): at least 2.0 mm for durability
2. Unsupported vs Supported Walls
- Unsupported walls (fewer than two supporting sides): Vertical ≥ 0.6 mm, Horizontal ≥ 0.3 mm
- Supported walls (two or more supporting sides): Same thickness thresholds apply.
3. Escape & Powder Removal Holes
Ensure internal cavities feature at least two escape holes, each at least 3.5 mm in diameter, to allow thorough powder removal and ensure clean, usable internal surfaces.
4. Text and Embossed/Engraved Detail Minimums
For raised (embossed) features:
- Horizontal: Depth 0.15 mm, Width 0.35 mm, Font Height 4.5 mm, Font Depth 0.3 mm
- Vertical: Depth 0.35 mm, Width 0.4 mm, same font specs
For engraved details:
- Horizontal: Depth 0.1 mm, Width 0.3 mm, Font Height 3 mm, Font Depth 0.3 mm
- Vertical: Depth 0.15 mm, Width 0.35 mm, same font height/depth
5. Assembly Tolerances & Clearances
- For separate parts intended to assemble:
- Features under 20 mm²: Clearance 0.2 mm
Features above 20 mm²: Clearance 0.4 mm
For integrated assemblies (printed together):
- Under 20 mm²: 0.3 mm
- Over 20 mm²: 0.6 mm
Enhancing Print Success & Reliability
Uniform Wall Thickness
Maintaining consistent thickness helps reduce warping and shrinkage. Consider hollowing or shelling thick components to achieve uniformity while saving material
Minimize Stress Concentrations
Avoid abrupt cross-sectional changes (e.g., thin protrusions from thick bases). Instead, use fillets or gradual transitions to lower stress and warping risks.
Manage Aspect Ratios & Warpage
Long, thin features (like ribs or cantilevers) are prone to warping. Incorporate ribs or drafts to strengthen them and avoid deformation.
Lattice Structures
Include gaps of at least 8 mm to ensure powder clearance from lattice structures and validate designs via small-scale test prints in the intended orientation.
Why These Guidelines Matter
- Printability: Thin or improperly supported structures risk failure during printing, powder removal, or post-processing.
- Strength & Accuracy: Consistent thickness and proper clearances help maintain mechanical integrity and geometric precision.
- Repeatability: Following these standards ensures parts remain consistent across multiple builds—vital for batch production and industrial use.
Summary Table
| Design Feature | Recommended Minimum / Consideration |
|---|---|
| Supported Walls | ≥ 1.5 mm (Nylon PA12 GF) |
| Unsupported Walls | Vertical ≥ 0.6 mm; Horizontal ≥ 0.3 mm |
| Delicate Features (Pins) | ≥ 2.0 mm |
| Escape Hole Diameter | ≥ 3.5 mm (at least two per cavity) |
| Embossed Features (H/V) | 0.15–0.35 mm depth, 0.35–0.4 mm width, font height ≥ 4.5 mm |
| Engraved Features (H/V) | 0.1–0.15 mm depth, 0.3–0.35 mm width, font height ≥ 3 mm |
| Assembly Clearance | Separate: 0.2–0.4 mm; Integrated: 0.3–0.6 mm |
| Wall Thickness Uniformity | Maintain uniformity, shell thicker parts |
| Stress Relief | Use gradual transitions (fillets) to avoid weak points |
| Lattice Design | Keep features ≥ 8 mm and test orientation |
Need help designing to SLS? Just ask!