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Design Guide

Selective Laser Sintering

Our design guidelines for selective laser sintering include important information to improve part quality, minimize costs, and reduce overall manufacturing time. By following the guidelines, you can produce high-quality parts, reduce expenses, and improve productivity.

If you have any questions regarding our design guidelines, you can contact our technical team by telephone, email or chat with us online.

Download Guidelines as PDF

Overview

SLS uses a laser to fuse particles of plastic powder together into a solid shape, layer by layer. Our machines have a laser diameter of 0.4mm (0.015”) with a laser offset of 0.25mm (0.009”).


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Maximum Build Volume
350mm x 350mm x 400mm (14” x 14” x 16”)
If your parts require specific tolerances, please include an engineering drawing along with the part. Parts designed with large flat planes will likely warp, so this should be avoided if tight tolerances are required.
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Tolerances
Nylon PA 12: ±0.25%, with a lower limit of ±0.25 mm

TPU: 0-30 mm (XY: ±0.35 mm, Z: ±0.90 mm) 30-50 mm (XY: ±0.40 mm, Z: ±1.15 mm) 50-80 mm (XY: ±0.50 mm, Z: ±1.50 mm)

If your parts require specific tolerances, an engineering drawing must be provided when requesting a manual quote, otherwise parts will be printed on a ‘best-effort’ basis.

 

Parts designed with thin, flat planes will likely warp, so this should be avoided if tight tolerances are required.

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Layer Height
100 Microns
The layer height is the overall Z resolution of the part; we avoid stepping artifacts on important features of your models by orienting the part(s) along the Z plane or at a 20 degree angle on all sides.
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Surface Finish
Uniform, Matte
Parts are bead blasted and have a uniform grainy matte texture, similar to ultra-fine sandpaper.

Wall Thickness

Thicker geometries and walls with variable thickness are at risk of deformation due to shrinkage and stress. In general, follow wall design rules for injection molding to achieve a more uniform and consistent part.

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Minimum Wall Thickness
0.8 mm - 1.0 mm (0.031” - 0.039”)

Supported walls connected to two or more sides and thick enough to support the model require a minimum thickness of 0.45mm (0.017”). We strongly recommend between 0.8mm - 1.0mm to ensure sufficient rigidity. Walls thinner than 0.45mm tend to over-thicken due to the laser over-sintering the thin features.

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Minimum Unsupported Wall Thickness
1.5 mm (0.059”)
Unsupported walls are connected on only one side or edge.
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Minimum Pin Diameter
0.8 mm (0.031” )
The minimum pin size depends on a combination of parameters such as; part orientation, nozzle diameter, and length of the pin.

Minimum Detail Size

The quality of engraved and embossed features depends heavily on part orientation and the resulting thermal effects of printing. It is best to orient text or other small details facing down on the XY plane, or oriented vertically on the ZX or ZY plane (though layer height will limit resolution).

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Engraved Details
Minimum Width and Depth: 0.5mm (0.019”)
Engraved details are recessed features on your model. Making these too small can result in closed gaps and loss of detail.
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Embossed Details
Minimum Width and Depth: 0.5mm (0.019”)
Embossed details are raised features on your model. These usually resolve better than engraved details. Extruded text should have a wall thickness of at least 1.5mm (0.059") when printed flat, and 2mm (0.079") when printed vertically.
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Text
Minimum point size: 14pt
0.5mm (0.019”) minimum line thickness and 0.5mm (0.019”) minimum depth or a minimum font size of 14 is suitable for every orientation. We recommend bold sans serif fonts.

Part Clearances

The mechanical performance of printed assemblies is sensitive to variables such as print orientation, layer height and machine tolerances. It is best to test and refine any mated parts before committing to a full production run.


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Minimum Clearance
Sensitive to wall thickness

Clearance is the distance between two moving parts on hinges, joints, mating parts, etc.

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Minimum Press Fit
Variable

When designing press fits, it is best to isolate the mating features and print a range of tests to dial in the offsets. Adding a chamfer to the leading edge can help ease entry.

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Hinges
Minimum: 0.6 mm (0.023")

It is possible to print mechanical linkages (eg. hinges, chains) already assembled. When designing for this scenario, clearance should be at least 0.6mm to prevent these features from fusing during the build.

Holes & Gaps

As a part is sintered, hollow features end up filled with powder which must be removed in post processing. Make sure to design parts with powder removal in mind, and avoid long winding channels, which cannot be cleared.


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Minimum Hole Size
Sensitive to wall thickness

Wall Thickness

1mm (0.039”)

3mm (0.11”)

6mm (0.22”)

 

Minimum Hole Diameter

0.5mm (0.019”)

0.6mm (0.023”)

0.7mm (0.027”)

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Minimum Gap Size
Sensitive to wall thickness

Wall Thickness

1mm (0.039”)

3mm (0.11”)

6mm (0.22”)

 

Minimum Gap Diameter

0.5mm (0.019”)

0.6mm (0.023”)

0.7mm (0.027”)

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Minimum Escape Hole Size
4 mm (0.015” )

Escape holes allow unsintered material inside hollow parts to be removed.

If you are using one escape hole, the minimum diameter is 10mm (0.39”).

For volumes larger than 50mm x 50mm x 50mm (1.96” x 1.96” x 1.96”), 2 holes are required, with a minimum diameter of 4mm (0.157”).

Part Geometry

Part geometry can be optimized for 3D printing to reduce material usage, increase strength and rigidity, and take advantage of machine capabilities.

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Fillets

Fillets can be used to reduce stress concentrations and increase the strength of your part.

When designing fillet features across inside and outside corners, it is best to have them share a common center point in order to maintain a consistent wall thickness.

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Bosses and Ribs

Bosses and ribs are an effective way to add strength and stiffness to a part while keeping material consumption to a minimum, this can also reduce build time and use less support material. If your part has tall, or thin unsupported features, using ribs can reduce warping and increase the strength and rigidity of those features.

Bosses and ribs can generally be matched to part thickness or up to 0.5mm (0.2 inches) less.

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Support Structures

Parts do not require physical support structures. Parts are supported by the surrounding powder in the build chamber. This powder material is removed using compressed air glass beads leaving no defects or residual powder on the final part.

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Infills
Parts are always produced with solid walls. Infills are not applicable for Selective Laser Sintering technology. 

Threads & Inserts

When possible, use metal fasteners and threaded inserts since they will perform much better than printed threads. Note that the heat from installing inserts may affect the surface finish of your part.


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3D Printed Threads

We recommend M6 thread sizes or larger, and use thread profiles designed for plastics. The rough surface produced from SLS printing will result in increased friction with connecting thread parts.

We recommend using an offset of 0.5mm to compensate for thermal shrinkage from the SLS processes which should allow a smoother threading process between the connecting parts.

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Tapping & Threading

Design parts with holes sized for tapping, or center marks for drilling a pre-tapped hole. You may need to reference a tap and drill chart to figure out which hole size corresponds to a given thread. 

Tapping removes material, puts pressure on the surrounding geometry, and fastener locations are often points of stress, so make sure there is enough material surrounding the tapped hole.

Tapping FDM parts often produces weaker threads that are not suitable for frequent re-use, especially when the threads run along the layer lines of the part.

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Inserts

Threaded inserts can be glued in, or heated and pressed in.

Heat set inserts require a soldering iron with an installation tip, which is used to heat the metal insert. This softens the plastic walls, allowing the insert to be pushed into the hole or boss before the plastic hardens around the insert.

The boss should be designed around the heat set insert intended to be used. The diameter should be set to the maximum diameter of the insert, keeping in mind the offset for the potential thermal shrinkage of the outside walls. We recommend adding a chamfer or fillet around the edge of the boss to allow a small amount of plastic to flow over the top edge of the insert.

Post Processing

While printed parts are highly functional and accurate, there are a variety of ways to modify them after printing to enhance durability or aesthetics.


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Sectioning, Joining, and Bonding

Parts too big to fit on the print tray can be split in CAD and printed in multiple parts, then glued or press fit. Use joinery features, such as tongue and groove, to ensure the sections are aligned and bond tightly.

Depending on orientation, material and other properties, an offset may be required to make sure the parts fit together properly. We recommend printing a small test part to dial in the offset before printing the full set of parts.

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Post-Machining
Parts can be machined to tighter tolerances using traditional or CNC subtractive manufacturing equipment.
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Coatings

The base color of SLS 3D printed parts is white, as printed. Parts can also be dyed black.

Parts can be coated with a lacquer, varnish or clear coat for various custom finishes. These finishes can also improve wear resistance, UV resistance, surface hardness, water tightness and limit marks and smudges on the surface of the part.

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Vapor Smoothing
Vapor smoothing is not applicable for Selective Laser Sintered parts.