Top 5 Design Mistakes to Avoid in SLS 3D Printing

By Sam Gribben
October 10, 2025
12:00 pm

Selective Laser Sintering (SLS 3D Printing) is one of the most powerful additive manufacturing processes for producing strong, functional parts — especially in engineering-grade materials like Nylon PA12 and Nylon PA12 Glass-Filled. However, even small design oversights can lead to warping, weak areas, or increased costs.

At SGD 3D, we see thousands of SLS parts each month. Here are the top five design mistakes to avoid when preparing your models for SLS 3D printing — and how to fix them.

1. Ignoring Minimum Wall Thickness

One of the most common issues we encounter is parts with walls that are too thin. SLS builds parts layer by layer using laser-fused powder, so unsupported thin walls can warp, crack, or fail entirely during printing or de-powdering.

Guideline:

Minimum wall thickness: 1.0–1.5 mm for rigid PA12
For PA12 Glass-Filled: 1.5–2.0 mm recommended
For tall, unsupported structures, increase to 2.5 mm+

Tip: If your part has fine details or snap-fit features, reinforce them with gradual transitions instead of sharp changes in thickness.

Checkout our other guide on applying textures to 3D printed parts using Formlabs PreForm software, we recommend applying these minimum wall thickness rules to parts before applying textures. Otherwise this can lead to NC (Non Conformance) defect parts.

2. Overlooking Drainage or Escape Holes in Hollow Parts

When printing hollow models, trapped powder can remain inside the part if there are no escape holes. This adds unnecessary weight and cost, and can even cause the part to fail during post-processing or vapour smoothing.

Guideline:

Include at least two escape holes (opposite sides where possible)
Recommended diameter: 6–10 mm minimum
Larger parts may need multiple escape holes for even powder removal

Tip: Use rounded transitions rather than sharp edges to reduce stress and improve airflow during cleaning.

3. Designing Features Too Close Together

SLS powder requires some clearance between moving or adjacent parts. Without sufficient spacing, parts can fuse together — especially in assemblies or hinges designed to move freely after printing.

Guideline:

Minimum clearance between moving parts: 0.5 mm
For tight tolerances or post-processed parts: 0.6–0.8 mm
Avoid nested or interlocking parts unless specifically designed for SLS

Tip: Always test-fit critical assemblies virtually before ordering your first print batch.

4. Forgetting About Part Orientation and Warping

Orientation affects both strength and surface finish. Large flat areas or long thin parts tend to warp slightly during the sintering process due to thermal stress. While SLS doesn’t require support structures, smart orientation can drastically improve accuracy.

Guideline:

Avoid long, thin parts with large flat bases
Add ribbing or internal lattice structures to maintain stiffness
Consider segmenting large parts and joining them post-print

Tip: If you’re unsure about orientation, mention your part’s functional surfaces when uploading to SGD 3D’s instant quote tool — our team will optimise the build setup for best results.

5. Skipping Fillets and Radii on Edges

Sharp internal corners create stress concentrations, while sharp external edges are prone to chipping during handling or smoothing. Rounded edges not only strengthen parts but also enhance the finish during vapour smoothing or dyeing.

Guideline:

Add fillets of 0.5 mm or more to internal corners
Use rounded transitions instead of abrupt thickness changes
Blend decorative or functional edges to improve strength and aesthetics

Tip: Smooth design = smoother finish. A small radius goes a long way in SLS part durability.

Final Thoughts

Designing for SLS isn’t difficult — but small improvements can have a big impact on print quality, cost, and performance. By following these guidelines, you’ll ensure your parts are stronger, more reliable, and easier to produce.

At SGD 3D, we specialise in engineering-grade SLS 3D printing using Nylon PA12 and Nylon PA12 Glass-Filled materials, with optional vapour smoothing and painting for production-quality finishes.

If you’d like a second opinion on your model before ordering, our team offers free design checks and instant online quotes.

👉 Upload your 3D file today and see the difference expert SLS manufacturing makes.