Technology · Design guidelines
SLS design guidelines for engineers
Practical guidance for designing parts for selective laser sintering: wall thickness, holes, clearances, powder escape holes, text, orientation and file preparation. The values are general starting points, confirmed for each project.
Read this first
This is general SLS guidance. The values are typical, conservative starting points, not guarantees. Final values depend on your geometry, material and orientation, and are confirmed in engineering review.
- Typical, conservative starting values
- Not guarantees, and not tolerances
- Confirmed for each part in engineering review
- All dimensions in millimeters
At a glance
Typical starting values
Use these values for a first check of your design. Each one is explained below, with the reasoning and the alternatives.
| Feature | Typical starting value | Notes |
|---|---|---|
| Wall thickness, non-structural | Typical starting value ≈ 1 mm | Notes Thicker for large or tall walls |
| Wall thickness, load-bearing | Typical starting value ≥ 2 mm | Notes Sized to the load case |
| Hole diameter | Typical starting value Ø ≥ 2 mm | Notes Drill or ream critical holes |
| Clearance between parts printed together | Typical starting value ≥ 0.5 mm | Notes For moving or interlocking parts |
| Powder escape holes | Typical starting value ≥ 2 × Ø 5 mm | Notes For hollow, enclosed volumes |
| Embossed or engraved detail | Typical starting value ≈ 1 mm high or deep | Notes Stroke width 0.5 mm or more |
| Tolerances | Typical starting value No general value | Notes Name critical dimensions in your request |
Guidelines
The guidelines in detail
Each guideline explains what happens in the process, gives a typical starting value and lists what to do and what to avoid.
Wall thickness
Typical value ≈ 1 mm non-structural · ≥ 2 mm load-bearing
Thin walls are possible in SLS, but they are fragile and can distort. About 1 mm is a typical minimum for walls that carry no load; plan 2 mm or more for walls that do.
Do
- Keep wall thickness as uniform as the design allows
- Use 2 mm or more for load-bearing walls, sized to the load case
- Thicken or rib large, thin walls
Avoid
- Walls thinner than about 1 mm, especially over large areas
- Thin, free-standing fins and tall unbraced walls
Holes and channels
Typical value Ø ≥ 2 mm
Small holes can partly close with fused powder or come out undersized. About 2 mm is a typical minimum diameter. Where a hole is critical, design it slightly undersized and drill or ream it to size after printing. Long, narrow internal channels are hard to clear of powder.
Do
- Use diameters of 2 mm or more
- Drill or ream holes that need an accurate fit
- Give internal channels openings at both ends for powder removal
Avoid
- Functional holes smaller than about 2 mm
- Long, narrow or tightly curved internal channels
Clearances for moving and interlocking parts
Typical value ≥ 0.5 mm
Parts printed together, such as hinges, chains or captive assemblies, need a gap so that the powder between them does not fuse. Plan about 0.5 mm or more, with a larger gap for large mating surfaces.
Do
- Keep at least 0.5 mm between surfaces that must move apart
- Increase the gap for large or long mating surfaces
- Leave openings so powder can be cleared from the gap
Avoid
- Gaps smaller than about 0.5 mm between moving parts
- Large flat surfaces facing each other at minimum clearance
Powder escape holes
Typical value ≥ 2 × Ø 5 mm
Unsintered powder stays trapped inside closed volumes. Hollow parts need at least two escape holes, about 5 mm in diameter or more, ideally at opposite ends so the powder can be blown out.
Do
- Add at least two holes of about 5 mm or more per hollow volume
- Place them at opposite ends, where they can be reached
- Plan how the holes will be closed if the part must be sealed
Avoid
- Fully enclosed cavities
- A single small hole for a large hollow volume
Embossed and engraved details
Typical value ≈ 1 mm · stroke ≥ 0.5 mm
Text, logos and markings stay legible when they are about 1 mm high or deep and their strokes are at least 0.5 mm wide. Bold, sans-serif fonts work best.
Do
- Use about 1 mm height for embossed and 1 mm depth for engraved details
- Keep strokes at least 0.5 mm wide
- Choose bold, simple fonts with generous letter spacing
Avoid
- Fine serifs and hairline strokes
- Shallow engravings that lose definition
Large flat areas and thickness changes
Typical value Ribs · gradual transitions
Large flat areas and abrupt changes in thickness cool unevenly and tend to warp. Break up flat areas with ribs or a slight curvature, and blend changes in thickness gradually.
Do
- Stiffen large panels with ribs or a slight curvature
- Blend thickness changes with tapers and fillets
- Core out thick sections, with escape holes for the powder
Avoid
- Large, thin, flat plates
- Sudden steps from thin to thick sections
Orientation
Typical value Chosen in engineering review
Parts are built in layers along Z, so surface finish, detail and strength vary with orientation. Shallow curved surfaces show layer steps. We choose the orientation in engineering review; tell us which surfaces and loads matter most.
Do
- Mark cosmetic surfaces and critical features on your drawing
- Tell us the main load directions
- Let us adjust orientation to balance surface quality, strength and cost
Avoid
- Assuming the same properties in every direction
- Specifying an orientation without saying why it matters
Threads and inserts
Typical value Coarse threads or heat-set inserts
Printed threads work best when they are coarse and not assembled often. For fine or frequently used threads, design a hole for a heat-set insert instead.
Do
- Use coarse thread profiles for printed threads
- Plan heat-set inserts for fine threads or repeated assembly, with the hole sized to the insert manufacturer’s recommendation
- Add a chamfer at the start of printed threads
Avoid
- Fine-pitch printed threads
- Printed threads that are screwed in and out repeatedly
Tolerances
Typical value Specified per part
Achievable tolerances depend on geometry, size, orientation and material, so we do not publish a general value. List your critical dimensions and tolerances in your quote request, and we confirm what is achievable in engineering review.
Do
- Mark critical dimensions on a drawing
- Separate functional tolerances from general ones
- Plan machining allowance where tight tolerances are needed
Avoid
- Applying tight general tolerances to the whole part
- Assuming machining or injection-molding tolerances
File preparation
Typical value STEP preferred
Send STEP files where possible. STL and 3MF work too: export them in millimeters, watertight and with enough resolution that curves stay smooth. Add a drawing for critical features.
Do
- Send STEP (preferred), or STL or 3MF in millimeters
- Check that meshes are watertight, without holes or self-intersections
- Export with a fine enough resolution for curved surfaces
- Include a drawing for critical dimensions and features
Avoid
- Meshes with gaps, flipped normals or unit errors
- Coarse tessellation that turns curves into facets
Checklist
Before you send your files
A quick pass over these points catches most issues before engineering review. Anything you are unsure about, note it in your request.
- Walls about 1 mm or more, and 2 mm or more where they carry load
- Holes 2 mm or larger, with critical holes marked for drilling or reaming
- At least 0.5 mm clearance between parts printed together
- Two or more powder escape holes of about 5 mm in every hollow volume
- Embossed or engraved details about 1 mm high or deep, with strokes of 0.5 mm or more
- Large flat areas stiffened with ribs, and thickness changes blended gradually
- Coarse printed threads or heat-set inserts planned
- Critical dimensions and tolerances named in the request or on a drawing
- STEP file, or a watertight STL or 3MF in millimeters, plus drawings for critical features
Start a project
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