A Guide to Materials for SLS 3D Printing
Understand materials available for SLS 3D Printing and their properties
Product designers and manufacturers have plenty of good reasons to use selective laser sintering (SLS). For one, SLS uses unsintered powder within the bed as a natural support. Doing so means fewer design restrictions and the ability to print overhangs and undercuts, complex internal channels, and even assemblies with moving parts. Further, there’s no need for post-print support removal, simplifying secondary processing while reducing project costs.
For this and other reasons, SLS is widely used for prototyping and low-volume production, especially when mechanical performance and design freedom matter. Functional prototypes of snap fits, hinges, clips, and interlocking parts that require real-world testing are common with SLS, particularly for components that will later be plastic injection-moulded as production quantities rise.
But it’s also a favourite for end-use parts such as custom brackets and housings, ducts, enclosures, jigs, fixtures, and other tooling. And those designing products like drones and wearables—lightweight airframes, for example, or orthopaedic braces—find that SLS, with its support-free printing, makes it easier to create the lattice structures needed to make parts lightweight yet strong.
That’s not to say it’s a perfect fit for every project, which explains why we offer multiple 3D printing technologies to match different needs. For instance, due to the nature of the sintered nylon powder, SLS parts typically have a matte, slightly grainy texture. As a rule, this surface is less than ideal for cosmetic components or tightly fitted assemblies without finishing. It’s also more porous than parts from other technologies, making them more likely to pick up dirt or oil from handling and product use.
Even after bead blasting, SLS parts can retain a tactile roughness. Additional steps like vapour smoothing are often necessary, especially for customer-facing products (as with many polymer-based processes). This step adds time and expense, but depending on the workpiece, it’s often quite affordable.
Materials Available for SLS 3D Printing
Some of these considerations are related to material selection. For many years, SLS was limited to nylon, but the offering has expanded with the technology's increasing popularity. Today, Protolabs customers can choose from the following polymers, each with distinct performance characteristics:
Unfilled Nylons
Offering an excellent balance of strength, durability, chemical resistance, and dimensional stability, PA12 (Nylon 12) is among the most widely used of SLS materials. PA 12 White is an economical material choice for functional prototypes and end-use parts. It offers high impact and temperature resistance, is very durable, and remains stable under a range of environmental conditions. The nylon material exhibits a white finish with a slightly rougher surface texture compared to other nylons.
Material Properties of Unfilled Nylons
| Tensile Strength | E-Module | Heat Deflection | Elongation | |
|---|---|---|---|---|
| PA12 White |
50 +/- 4 MPa
|
2000 +/- 200 MPa
|
163°C
|
11% +/- 4%
|
| PAx Natural |
40 +/- 5 MPa
|
1300 +/- 200 MPa
|
105 ± 5 °C
|
>60%
|
Filled Nylons
Material Properties of Filled Nylons
| Tensile Strength | E-Module | Heat Deflection | Elongation | |
|---|---|---|---|---|
| PA12 40% Glass-Filled |
42 +/- 4 MPa
|
3600 +/- 400 MPa
|
157 °C |
5 +/- 2%
|
| PA12 Carbon Filled Black |
85 +/- 5 MPa
|
8300 +/- 400 MPa |
170 +/- 5 °C
|
3.2 +/- 2%
|
3D-Printed TPU
Thermoplastic Polyurethane like the TPU88-A Black we use is a flexible, rubber-like material often used for gaskets, seals, and cushioning elements such as those found in protective gear, especially where a soft-touch feel or impact resilience is needed. It delivers high elasticity and abrasion resistance, as well as reliable performance under repeated flexing or compression. Despite this, it lacks the structural rigidity of nylon-based powders, so the material is less suitable for load-bearing parts or those that are dimensionally critical.
Material Properties of SLS TPU
| Tensile Strength | E-Module | Elongation | |
|---|---|---|---|
| TPU-88A Black |
20 +/- 5 MPa
|
72 +/- 16 MPa
|
520 +/- 50%
|
Secondary Operations for SLS 3D-Printed Parts
Corner radii also help to ease the removal of any leftover powder that might remain after printing, an operation that occurs during post-process blasting and one that all SLS parts receive. Many also receive vapour smoothing, a technique used to improve the surface finish of 3D-printed parts—particularly those made from SLS or MJF nylon. Here, finished workpieces are exposed to a controlled chemical vapour, slightly melting the outermost surface and causing it to flow and re-solidify into a smooth, somewhat glossy sealed layer.
Dyeing and painting are also possible. As suggested earlier, parts made of PA12 White can be dyed blue, green, red, yellow, and black, although as the design tip just mentioned states, “additional colour options—like orange or purple—can be supported but they are not included in our standard offering, so it will be more expensive as they are mixed on a per-order basis.”
Finally, Protolabs now offers a ceramic-filled spray coating called Cerakote. Originally from the firearms industry and popular on custom-finished handguns and rifles, Cerakote is applied to parts after printing and then cured during a baking process. It is an incredibly versatile finish that is resistant to scratches, heat, and many chemicals, making it a great choice for both functional and cosmetic applications.
