3D printing - design guide for SLS components: 12 mistakes that cost time & money

In additive manufacturing, selective laser sintering (SLS) has established itself as a powerful process for the production of complex and functional components. However, despite the enormous design freedom that SLS offers, there are some pitfalls that can cost both time and money. This guide shows you the most common design errors in SLS components and how you can avoid them.

1. Insufficient wall thickness

One of the most common mistakes is not using the minimum wall thickness. For SLS components, this should be at least 0.8 mm. Walls that are too thin lead to fragile structures that can break during the printing process or during post-processing. This not only leads to rejects, but also delays production schedules and increases costs.

Tip: Plan with a wall thickness of 1-1.5 mm for optimum results. For particularly stressed areas, we recommend a reinforcement of 2-3 mm.

2. Lack of stress relief holes

Massive solids store a lot of heat during SLS printing. Without stress relief holes or recesses, internal stresses arise that can lead to distortion or even cracks.

Tip: Provide larger, solid components with strategically placed stress relief holes or integrate internal structures that reduce the material volume without compromising stability.

3. Detailed structures that are too small

SLS offers a high level of detail, but there are technical limits. Structures smaller than 0.5 mm are often not reliably reproducible and can lead to misprints.

Tip: Keep detailed structures such as small studs, knobs or engravings above 0.5 mm. Note that vertical details are reproduced better than horizontal ones.

4. Ignoring the build direction

The build direction has a significant influence on the mechanical properties and surface quality of SLS components. Many designers overlook this critical aspect.

Tip: If possible, position functional surfaces and aesthetically important areas so that they do not point in the Z direction (vertically), as this is where the layer lines are most clearly visible.

5. Lack of powder softening system

A major advantage of SLS is that no support structures are required. However, it must be possible to remove the unsintered powder from cavities. Closed hollow bodies without openings lead to trapped powder, which increases the weight and can impair functionality.

Tip: Plan at least two openings with a diameter of 3-5 mm for hollow bodies - one for powder leakage and one for air equalization.

6. Overlooking tolerances

SLS components have production-related tolerances that must be taken into account in the design. Ignoring these tolerances leads to fitting difficulties during assembly.

Tip: Calculate with tolerances of ±0.2 to ±0.3 mm depending on the component size. For hinges and moving parts, you should allow a gap of at least 0.5 mm.

7. Unsuitable fits for mechanical connections

The specific material properties of sintered polyamide are often not sufficiently taken into account for plug-in connections or snap-fasteners.

Tip: Sintered PA12 is less flexible than injection-molded material. Therefore, plan more generous geometries for snap-fit connections and avoid structures that are too delicate and can break easily.

8. Disregarding possible component shrinkage

SLS materials, especially polyamides, are subject to possible shrinkage during cooling. If this is not taken into account in the design, the final components will not correspond to the desired dimensions.

Tip: Modern slicer software automatically compensates for material shrinkage. Nevertheless, you should carry out test prints for high-precision applications and adjust the design if necessary.

9. Inefficient component positioning in the installation space

The arrangement of several components in the print space has a significant impact on costs. Inefficient placement wastes valuable installation space and drives up production costs

Tip: Design your components so that they can be arranged as compactly as possible in the print space. Nesting software can help to find the optimal arrangement.

10. Ignore post-processing requirements

Freshly printed SLS components have a slightly rough, grainy surface. If this is not acceptable for the intended application, post-processing steps will be required, resulting in additional costs.

Tip: Consider the required surface quality as early as the design phase. Surfaces that are to be machined later should be provided with appropriate allowances.

11. Underestimating the structural requirements

SLS-printed parts have different mechanical properties than injection molded or milled parts. Ignoring these differences can lead to component failure.

Tip: Reinforce critical areas and perform FEM simulations on stressed components to check stability. Note that SLS components have anisotropic properties - the strength in the Z direction is lower than in the X-Y direction.

12. Neglecting economic aspects

Not every component is optimally suited for SLS. Sometimes conventional manufacturing processes such as CNC milling or injection molding are more economical, especially for higher quantities.

Tip: Critically evaluate whether SLS is the right choice for your specific component. Use the design freedom of SLS specifically for complex geometries and consolidated assemblies that would not be feasible with conventional processes.

Intelligent design saves time and money

SLS technology offers fascinating possibilities for innovative products and solutions. In order to fully exploit this potential, it is worth knowing the specific requirements and limitations of the process and taking them into account in the design. With the right guidelines, you can not only save time and money, but also optimize the quality and functionality of your components.

At EVG, we support you with our many years of experience in the development and implementation of optimum solutions for your applications.

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