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-molded as production quantities rise.
But it’s also a favorite 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 orthopedic 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 vapor 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. We offer three grades of PA12—White, Black, and Value. The latter of these is appropriately named; made from partially recycled powder, it sacrifices some of the bright white color of PA12 White (PA650) but makes up for it by being the lowest cost SLS material option. Parts made from PA12 Black achieve their color from post-print dyeing.
Regardless of its color, PA12 is a versatile, engineering-grade nylon widely used in SLS 3D printing due to its excellent balance of strength, durability, chemical resistance, and dimensional stability. It produces parts that are tough yet lightweight, making it a go-to material for functional prototypes and end-use components across many automotive, medical, industrial, and consumer applications.
Unlike PA12 Black (in which parts are dyed that color after printing), PA11 Black (PA850) is pre-pigmented at the powder level, resulting in a consistent black color straight from the printer. Derived from castor oil (and not petroleum, as with PA12 and, indeed, most nylons), it is bio-based. This quality tends to make it the first choice for orthotics and wearables, for which flexibility, biocompatibility, and sustainability are key. It's also more ductile and impact-resistant than PA12, making it a better choice for flexible, load-bearing, or bio-based applications like custom medical devices or living hinges.
Material Properties of Unfilled Nylons
| Tensile Strength | E-Module | Heat Deflection | Elongation | |
|---|---|---|---|---|
| PA12 Black | 46 MPa | 1,900 MPa | 175°C | 13% |
| PA12 White | 50 MPa | 2,000 MPa | 177°C | 11% |
| PA12 Value | 46 MPa | 1,900 MPa | 190°C | 13% |
| PA11 Black | 52 MPa | 1,800 MPa | 188°C | 30% |
Filled Nylons
PA614-GS is a PA12 nylon reinforced with 40% glass fiber, giving it a light gray appearance as well as significantly greater stiffness and dimensional stability than unfilled nylon. With its high strength, rigidity, and precision, PA614-GS is well suited for structural parts, enclosures, jigs and fixtures, and other components that require tight tolerances and must withstand mechanical loads or wear.
PA620-MF is also based on PA12 and has a color similar to PA614-GS but depends on minerals for its strength. This improves heat deflection and rigidity while reducing warping, so PA620-MF is a great choice for automotive components like HVAC ducts, electronic housings, and other applications requiring thermal stability. It's also lighter and less brittle than glass-filled, so it provides moderate reinforcement without adding significant weight or sacrificing impact resistance.
Material Properties of Filled Nylons
| Tensile Strength | E-Module | Heat Deflection | Elongation | |
|---|---|---|---|---|
| PA12 40% Glass-Filled (PA614-GS) | 45 MPa | 3.500 MPa | 157°C | 5% |
| PA12 Mineral-Filled (PA620-MF) | 38 MPa | 3,100 MPa | 184°C | 3% |
3D-Printed Polypropylene (PP)
As its name suggests, parts made with Polypropylene Natural exhibit an off-white or cream color. It is a lightweight, semi-flexible, and chemically resistant material, often used for living hinges, fluid-handling components, and snap-fit parts. PP exhibits lower strength than nylon but excels in chemical and fatigue resistance—think medical components like nozzles, specimen closures, and tubing connectors, as well as caps and clips for industrial applications.
Material Properties of SLS Polypropylene:
| Tensile Strength | E-Module | Elongation | |
|---|---|---|---|
| Polypropylene | 18 MPa | 850 MPa | 15% |
3D-Printed TPU
Thermoplastic Polyurethane like the TPU70-A 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 | 4 MPa | 40.5 MPa | 210% |
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 vapor 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 vapor, 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 color 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.
