How to Choose a SLS 3D Printing Material

The material you choose for an SLS part decides whether that part survives its job, and a wrong choice shows up as a clip that cracks on assembly, a bracket that sags next to a motor, or a part that costs far more to print than it should.

Two kinds of requirement decide the choice.

Hard limits come first: a certificate the part must carry, and what your printer and facility can run.

Performance comes next: the load and stiffness the part needs, how far it has to bend or flex, whether it must be soft, and the temperature it works at under load. Chemical exposure narrows the shortlist further, and accuracy, finish and cost per part decide between the powders that pass.

This guide takes each factor in turn, covers SLS materials beyond our range, and ends with a comparison of our seven SLS powders.

Bottom line

• Start with a general-purpose nylon (PA12 or PA NEXT) and move off it only when a specific requirement rules it out.
• Move to PA NEXT or PA11 when the part must bend a lot, to a glass-bead grade when it must stay stiff or hold shape hot under load, and to TPU when it must be soft.
• Flame ratings and food contact point to a certified grade, which the RMS220 can run as a third-party powder you qualify under its open material licence. Aggressive chemicals point to PP. Sustained high heat points to PEEK, which needs a high-temperature system or a service bureau.

Start With the Part, Not the Powder

Datasheets are easy to read in the wrong order. Answer these questions about the part first, then open the datasheets:

• Does it need a certificate, such as a flame rating, food-contact approval, biocompatibility or ESD protection?
• What load does it carry, and how much can it deflect under that load?
• How far does it have to bend: once at assembly, or thousands of times?
• Does it need to be soft or rubbery?
• Which way does the load run relative to the build layers?
• What is the hottest it gets while it is loaded?
• What does it touch: oil, fuel, cleaning chemicals, water, sunlight, skin, food?

A certificate requirement can rule a powder out on its own, so settle that question first. Accuracy, finish and cost per part come after the other six, because they only decide between powders that already pass. After a short overview of the SLS materials available, the sections below answer the performance questions in order, then cover accuracy, finish, certificates, printer limits and cost.

What SLS Can Print Beyond PA12

PA12 is the default SLS material across the industry because it sinters predictably, holds dimensions well and reuses well. It is not the only option, and some parts need something else entirely. Here is the wider range, including materials we do not offer.

Unfilled nylons: PA12, PA11 and PA6

PA12 (nylon 12) is the most widely used SLS powder and the default choice for housings, brackets and functional prototypes. PA11 (nylon 11) is a more ductile nylon, usually made from castor oil, that gives up a little stiffness for much more stretch before breaking. On our datasheets PA12 reaches 6–9% elongation at break and PA11 33–41%, at a similar tensile strength of around 50 MPa (7.3 ksi). PA6 (nylon 6) is stronger and stiffer than PA12 but harder to process, so fewer machines and service bureaus run it.

Filled nylons: glass, carbon, mineral and aluminium

Filled nylons are PA11 or PA12 powders blended with glass beads or fibres, carbon fibre, minerals or aluminium to raise stiffness and heat resistance. The trade-off is elongation. Glass-filled, carbon-filled and aluminium-filled PA12 typically break at 3–5% elongation, against 6–9% for our unfilled PA12 and over 30% for PA11. Carbon fibre gives the most stiffness per gram. Mineral-filled PA12 offers some of the highest heat deflection temperatures among the filled nylons.

Elastomers: TPU and PEBA

TPU (thermoplastic polyurethane) is the standard flexible SLS powder, usually sold at around 90 Shore A. PEBA (polyether block amide) is an elastomer used where a part needs more rebound and softness than TPU gives.

Polypropylene

Polypropylene (PP) is a light, chemically resistant thermoplastic used for fluid-handling parts, containers and living hinges. It also resists fatigue well. The trade-off is process difficulty: it warps more and bonds between layers less strongly than nylon.

High-temperature polymers: PEEK and PEKK

PEEK and PEKK are high-performance polymers for parts that work at temperatures well beyond the range of nylon, mainly in aerospace and demanding industrial service. PEEK melts at around 343°C (649°F), so it needs a dedicated high-temperature SLS system. Both the machines and the powders cost considerably more than nylon SLS.

Specialty grades

Specialty grades are nylon powders modified to meet a specific certification or electrical requirement. Examples include flame-retardant PA12 rated UL94 V-0, food-contact PA11 and PA12, PA11 with USP Class VI biocompatibility, and electrostatic-dissipative (ESD) PA11, typically 10⁶–10⁹ Ω. Whether you can get them depends on your printer’s material licence or your service bureau’s catalogue.

What a 220°C-class printer like the RMS220 can run

The Raise3D RMS220 is a compact SLS printer with a maximum powder temperature of 220°C (428°F). That range covers the PA11 and PA12 families and TPU, which is what our seven powders are: PA12, PA NEXT, PA11, PA12 GB, PA NEXT GB, TPU 86A Black and TPU 86A White.

PEEK and PEKK process far above that ceiling, so the RMS220 cannot run them. PP, carbon-filled nylons and certified nylon grades process within it, so for those the question is the catalogue, not the temperature. None of them is in our current range, and neither is PA6.

Two routes cover them. Under the Open Material Program the RMS220 can run selected third-party powders, and an optional fully open material licence lets you run powders you qualify yourself, with no annual material authorisation fee. We or your reseller can confirm which third-party powders are already qualified for your application. For PEEK, PEKK and anything else above 220°C, use a high-temperature system or a service bureau.

How Much Load and Stiffness the Part Has to Carry

Stiffness and strength matter because they decide whether a part keeps its shape and survives the loads it carries in service. Tensile strength tells you the load at which the material fails. Tensile modulus tells you how far it deflects under load before that point. For brackets, jigs and fixtures, modulus usually decides the material, because a fixture that bends 0.5 mm (0.02 in) under clamping load is scrap long before it breaks.

The unfilled nylons all sit close together on strength. On our datasheets PA12 reaches 50 MPa (7.3 ksi), PA NEXT 45 MPa (6.5 ksi) and PA11 53–54 MPa (7.7–7.8 ksi). Glass beads barely move that number: PA12 GB reaches 49 MPa (7.1 ksi). What they change is stiffness. Tensile modulus rises from about 1,790 MPa (260 ksi) for PA12 to 2,800 MPa (406 ksi) for both glass-bead grades, roughly 55% higher.

Deflection under a given load scales inversely with modulus. The same bracket printed in PA12 GB deflects 1,790 ÷ 2,800 ≈ 0.64 times as far as in PA12, about 36% less, with no change in geometry.

Where the part can change shape, geometry is the stronger lever. Bending stiffness scales with the cube of wall thickness, so a wall about 16% thicker gives the same gain as the switch to a glass-bead grade. The material change pays off when the part can’t grow, because it has to fit an existing envelope or mate with an existing part.

Materials that fit: PA NEXT GB and PA12 GB from our range. From outside it, carbon-filled PA11 or PA12 give more stiffness per gram, and glass-fibre or mineral-filled PA12 are further options. All of them trade elongation for stiffness, which the next section deals with.

How Far the Part Has to Bend Before It Breaks

Ductility matters because it decides whether a part can bend, flex or take an impact without cracking. It is measured as elongation at break, the percentage a test bar stretches before it fails. It decides the material for snap-fits, clips, living hinges and anything that gets dropped. On our datasheets the range is wide:

• PA12: 6–9%
• PA NEXT: 30–36%
• PA11: 33–41%
• PA12 GB and PA NEXT GB: 3–4.5%

Here is a screening check for a cantilever snap-fit. Peak strain at the root is roughly ε = 1.5 × y × t ÷ L², where y is the deflection, t the thickness at the root and L the hook length. Take a hook 15 mm (0.59 in) long and 2 mm (0.079 in) thick that deflects 1.5 mm (0.059 in) to engage:

ε = 1.5 × 1.5 × 2 ÷ 15² = 4.5 ÷ 225 = 0.02, or 2%

PA12’s weakest-direction elongation of 6% leaves a 3× margin, which is fine for a clip assembled a few times. A glass-bead grade at 3% leaves 1.5×, and that hook will likely crack within a few cycles if its bending runs across the layers. PA NEXT or PA11 at 30% or more leaves over 15×, which is why they are the default for clips that get used every day.

Elongation at break is a screening number, not a design allowable. For features flexed many times, keep peak strain well below the Z-direction value and confirm the design with a cycle test on a printed sample. The ductile grades are what give you that room.

For living hinges, PA11 and PA NEXT are the options in our range. From outside it, PP is the classic living-hinge material.

Whether the Part Needs to Be Soft and Flexible

Flexibility matters because parts that grip, seal, cushion or conform must deform under load and then recover their shape, which rigid nylons cannot do. In SLS, that means an elastomer, usually TPU. Hardness is measured on the Shore A scale. Around 90A is firm, like a shoe sole: you can flex a thin section by hand, but you cannot squash a thick block.

We offer TPU 86A in black and white. On our datasheets, the black grade reaches 9.9 MPa (1.4 ksi) tensile and 505% elongation in X, and the white grade reaches 16.5 MPa (2.4 ksi) and 616%. Despite the 86A in the name, printed parts measure 90–93 Shore A (ISO 868), so design to the measured value. If you need softer behaviour than the material gives, change the geometry: lattice density and wall thickness set how soft an insole or helmet liner feels far more than the powder does. Our insole and helmet-lining reference parts are designed that way.

Two practical notes. TPU needs thicker walls than nylon. As a starting point, design TPU walls at 1.5 mm (0.06 in) or more, against 0.8 mm (0.03 in) for PA12. TPU also shows more dimensional expansion than the nylons, so allow for it on mating features.

Materials that fit: TPU 86A Black and White from our range. From outside it, PEBA gives more rebound, and softer TPU grades exist for cushioning parts.

Which Direction the Load Comes From

Load direction matters because SLS parts are usually weaker and less ductile across the build layers (the Z direction) than along them. For the nylons, the difference in tensile strength is small. Elongation is a different story, and it is the number that matters for anything that bends. Our datasheets give X- and Z-direction values, so you can see the gap directly:

The practical rule is to orient the part so that the bending strain runs in the XY plane. When the geometry won’t allow that, design to the Z value. TPU is the case to watch: it loses about 35% of its tensile strength in Z, so a flexible strap printed standing up is noticeably weaker than the same strap printed flat. If a supplier’s datasheet gives only XY values, ask for Z data whenever the part is loaded through its layers.

How Hot the Part Gets in Service

Service temperature matters because nylon parts lose stiffness quickly as they heat up under load: a PA12 bracket that is rigid at room temperature can start to deform at around 50°C (122°F) under heavy load. It is also the easiest factor to misread on a datasheet. Heat deflection temperature (HDT) is measured by heating a loaded bar until it bends a set amount, and the result depends heavily on the load. We publish HDT at 1.8 MPa (264 psi), the heavier of the two standard loads, and our PA12 comes in at 51°C (124°F). Many SLS datasheets quote HDT at 0.45 MPa (66 psi) instead, where nylon 12 powders typically rate around 150–175°C (300–350°F). The same powders tested at 1.8 MPa typically come in below 100°C (212°F). Read without the load, those numbers look like two different classes of material.

The mechanism explains the gap. PA12 has a glass transition at around 40–50°C, above which its amorphous regions soften. Under a light load, the crystalline structure holds the bar up almost to the melt. Under a heavy load it gives way just past the glass transition. Glass beads stiffen the softened matrix, which is why the filled grades hold up far better at 1.8 MPa. PA NEXT GB reaches 114–115°C (237–239°F) at 1.8 MPa, against 45–48°C (113–118°F) for unfilled PA NEXT. PA12 GB is rated at 0.45 MPa, at about 173°C (343°F), so compare it only with other 0.45 MPa values.

Three rules follow from this:

• Compare HDT only at the same load.
• For a part carrying real load near heat (a bracket beside a motor, a duct clip in an engine bay), design to the 1.8 MPa value. For a lightly loaded cover, the 0.45 MPa value is closer to reality.
• HDT is a short-term test, not a continuous-service rating. Leave margin, and test the part at temperature if it matters.

Materials that fit: PA NEXT GB from our range for parts under heavy load at heat, and PA12 GB for lightly loaded parts at heat. From outside it, mineral-filled PA12 performs well, and PEEK or PEKK on a high-temperature system is the answer when the part lives well above nylon’s range.

Chemicals, Moisture and UV in the Operating Environment

The operating environment matters because chemicals, moisture and sunlight can weaken, swell or degrade a part over time, even when it is never overloaded. PA11 and PA12 generally resist oils, fuels, greases and many common solvents, which is why they are used for automotive brackets and fluid-line clips. Strong acids and some oxidising cleaners attack nylon. Check the specific chemical, at the service temperature, against the datasheet or with an immersion test.

Moisture matters more for PA11 than for PA12, because PA11 absorbs more water, and absorbed water slightly changes dimensions and stiffness. TPU 86A is rated for hydrolysis and UV resistance, which suits outdoor and wet-environment soft parts.

Materials that fit: PA12, PA NEXT and PA11 for oil and fuel contact, and TPU 86A for wet or outdoor flexible parts. From outside our range, PP is the choice when the part sits in aggressive chemicals.

Dimensional Accuracy and Warpage by Material

Material choice matters for accuracy because each powder shrinks, warps and expands differently as it cools, which changes how closely printed parts match the CAD model. There is no single tolerance figure for SLS. Accuracy depends on the material, the geometry, how the build is nested and how it cools. Material still sets the starting point:

• PA11 suits thin walls and fine detail.
• TPU expands and deforms more than the nylons, so allow extra clearance on mating features.
• Glass-bead grades warp less on long, flat parts, because the beads reduce shrinkage.
• PP, from outside our range, warps more than nylon.

Geometry helps too. Keeping walls near a uniform thickness, around 3 mm (0.125 in) for warp-prone parts, often reduces distortion more cheaply than a material change. For assemblies with tight fits, print a representative sample in the candidate powder and measure it before committing a production batch.

Surface Finish, Colour and Post-Processing

Surface finish and colour matter because they decide whether a part can be used as printed or needs extra post-processing time and cost. SLS parts come out with a fine, slightly grainy matte finish and almost no visible layer lines. Our nylons are black only, so rigid parts cannot be dyed to a colour. Paint or coat them when colour matters.

Finish differences between powders are real but smaller than the differences post-processing makes. PA NEXT packs denser than PA12 (powder bulk density 0.66 against 0.52 g/cm³), and after bead blasting it often gives a finish usable for prototypes without dyeing or coating. Vapour smoothing seals the surface of PA11, PA12 and PP parts for a near-moulded finish. Dyeing works on light-coloured powders.

Materials that fit: PA NEXT for the best finish straight from bead blasting in our range. TPU 86A White for flexible parts where colour or a light finish matters. It is the only white powder in the range and the one to start from for dyed parts. Test the dye on a sample print before committing a batch.

One process note: PA11 printed in air instead of nitrogen shows orange peel on the surface. That is covered below.

Certifications the Part Has to Meet

Certifications matter because a part that needs a flame rating, food-contact approval or biocompatibility can only be made from a powder, and a process, qualified to that standard. Settle this requirement before comparing any other property, because it rules out powders before any other factor does. Common requirements are flame ratings (UL94 V-0), food contact, biocompatibility (USP Class VI or ISO 10993) and ESD protection.

Most of our powders carry RoHS, REACH and TSCA declarations. Those cover restricted substances. They are not flame, food-contact or biocompatibility certificates, and none of our seven powders carries one of those today. The certified powders listed earlier (flame-retardant PA12, food-contact PA11 and PA12, USP Class VI PA11, ESD PA11) are available from other powder suppliers and through service bureaus. On the RMS220, the fully open material licence lets you run a certified third-party powder you qualify yourself, such as an FDA-compliant grade.

A certificate belongs to the powder plus a validated process, not to the powder alone. Budget for the qualification work, not just the material.

What Your Printer and Facility Can Run

Printer and facility limits matter because a powder is only usable if your machine reaches its processing temperature and your site can supply the atmosphere it needs. Three constraints apply.

Temperature. The RMS220’s 220°C (428°F) ceiling covers nylons and TPU and rules out PEEK and PEKK.

Atmosphere. Nylon oxidises at bed temperature, and oxidised powder ages faster and needs more fresh powder per build. The RMS220 prints in air or nitrogen, and its built-in nitrogen generator needs a compressed-air supply. The powders differ:

PA11 needs an external nitrogen generator or tank, not just the built-in unit. That adds equipment and running cost, so price it in alongside the powder.

Changeover. Switching powders on the RMS220 takes 45 minutes to an hour, including clearing the powder hopper, so a lab testing several materials can do it within a shift. Keep virgin, used and blended powder for each material in separate, labelled containers to avoid cross-contamination.

What Drives Cost per Part

Cost per part matters because it decides whether a part is economical to print in a given powder, and it depends on more than the powder’s price per kilogram. Three levers decide it: powder price, refresh rate and packing density.

The refresh rate is the share of fresh powder mixed into each build. Roughly, the fresh powder you consume per build equals the refresh rate times the powder you load. Take an illustrative build with 10 kg (22 lb) of powder loaded and 1.5 kg (3.3 lb) of finished parts:

So PA11 consumes about 2.5 times the fresh powder per kilogram of parts that PA NEXT does, before any difference in price. Printing PA12 in air at 50% instead of nitrogen at 30% raises fresh-powder use by about two-thirds.

The model assumes the used powder each blend doesn’t need is set aside. Each build returns up to 8.5 kg (18.7 lb) of used powder, and at a 50% refresh rate only 5 kg (11 lb) of it goes into the next build. Build height and how much used powder you keep both shift the figures, but the ratios hold.

Part density adds a smaller effect. PA NEXT parts come out at 1.13 g/cm³ against 1.02 g/cm³ for PA12, so the same part is about 10% heavier. Packing density adds a larger one, because the more parts you nest into each build, the more of the loaded powder turns into product. Our reference builds show it:

These figures are cost per finished part, covering powder, labour, energy, equipment depreciation and key consumables. Post-processing and part geometry move the real figure for your part.

The cheapest part on that list uses the powder with the highest refresh rate. It is small, and 192 of them share each build, so the fresh-powder cost is spread across all of them. For small parts, nesting density often moves cost per part more than the choice of powder.

Raise3D’s Seven SLS Powders Compared

Typical values from our technical data sheets, tested to ISO 527-2 (tensile) and ISO 75-2 (HDT). PA12 GB is rated for HDT at 0.45 MPa: 173°C (343°F). Your parts will vary with geometry, orientation and process settings.

PA12 Black

PA12 Black is a general-purpose nylon 12 powder for functional prototypes, housings, connectors, jigs and small-batch end-use parts. It has a tensile strength of 50 MPa (7.3 ksi), 6–9% elongation at break and low warpage, which makes it a dependable default for rigid parts. It prints in nitrogen at a 30% refresh rate, or in air at 50%. Its limits are low ductility for snap-fits that flex often and an HDT of 51°C (124°F) at 1.8 MPa, so it is not suited to loaded parts near heat. For new applications, we recommend PA NEXT Black for better print performance. PA12 remains the choice where a part or process is already qualified in PA12.

PA NEXT Black

PA NEXT Black is a polyamide powder we developed for parts that bend, flex or carry load from several directions. It has a tensile strength of 45 MPa (6.5 ksi) in X and Z alike and 30–36% elongation at break, about four times that of PA12. It has the lowest refresh rate of our nylons, 20% in nitrogen, and it can also print in air at 50%. It is about 10% less stiff than PA12 and offers no advantage at elevated temperature, with an HDT of 45–48°C (113–118°F) at 1.8 MPa.

PA11 Black

PA11 Black is a nylon 11 powder for tough, impact-resistant parts, thin walls and complex geometry. It has the highest tensile strength and elongation among our nylons: 53–54 MPa (7.7–7.8 ksi) and 33–41%. Typical uses are clips, living hinges, orthotic supports and thin-walled housings. It requires an external nitrogen supply of over 99.9% purity, with chamber oxygen kept below 2%, and a 50% refresh rate. Both requirements raise its running cost compared with the other nylons.

PA12 GB Black

PA12 GB Black is a nylon 12 powder reinforced with glass beads for stiff, dimensionally stable parts. Its tensile modulus is 2,800 MPa (406 ksi), about 55% higher than unfilled PA12, while its tensile strength stays at 48–49 MPa (7.0–7.1 ksi). It suits structural brackets, fixtures and parts that must stay flat, and it prints at a 30% refresh rate in nitrogen. Elongation at break drops to 3–4.5%, so it is not suited to snap-fits. For new applications, we recommend PA NEXT GB Black for better print performance and part quality. PA12 GB remains the choice where a part is already qualified in it.

PA NEXT GB Black

PA NEXT GB Black is a glass-bead-reinforced version of PA NEXT for stiff parts that work at elevated temperature. It has a tensile modulus of 2,800 MPa (406 ksi) and an HDT of 114–115°C (237–239°F) at 1.8 MPa. Its properties vary little with direction: elongation at break falls only from 4.5% in X to 4% in Z. It suits fixtures, brackets and ducts exposed to heat, and it prints at a 30% refresh rate in nitrogen. Like all glass-bead grades, it breaks at low strain and is not suited to snap-fits.

TPU 86A Black

TPU 86A Black is a thermoplastic polyurethane elastomer powder for soft, flexible parts. It has a tensile strength of 9.9 MPa (1.4 ksi) and stretches to 505% before breaking in the X direction. Typical uses are grippers, seals, gaskets, protective padding and footwear. It prints at a 20% refresh rate in nitrogen. Its tensile strength falls by about 35% in the Z direction, so flexing features should be oriented flat in the build.

TPU 86A White

TPU 86A White is the white version of our TPU 86A elastomer powder, for flexible parts where colour or a light finish matters. It covers the same uses as the black grade. On our published data it is also stronger, with 16.5 MPa (2.4 ksi) tensile strength and 616% elongation at break in the X direction. It prints at a 20% refresh rate in nitrogen.

We also offer TPU 90A Black, and recommend TPU 86A Black in its place.

Common Parts and the Powder to Start With

Mistakes That Lead to the Wrong Powder

• Choosing by tensile strength. The unfilled nylons are within about 10 MPa of each other. Elongation, modulus and HDT are what separate them.
• Comparing HDT figures measured at different loads. The same nylon 12 can be rated above 150°C at 0.45 MPa and below 100°C at 1.8 MPa.
• Ignoring the Z direction. Parts flex and fail across the layers first, and TPU loses about a third of its strength there.
• Pricing powder per kilogram instead of per part. A cheaper powder at a 50% refresh rate can cost more per part than a dearer one at 20%.
• Treating nitrogen as optional. For PA11 it isn’t, and for every grade, printing in air raises powder consumption.

Material Selection Checklist

• Certification requirement confirmed, or none
• Peak load and allowable deflection defined
• Peak strain on clips and hinges calculated and compared with Z-direction elongation
• Softness requirement defined in Shore A, or none
• Load direction relative to the layers known, and orientation chosen
• Maximum temperature under load known, and HDT compared at the matching load
• Chemicals, moisture and UV exposure listed
• Tight fits identified for a sample print
• Finish and colour requirement defined
• Printer temperature, atmosphere and nitrogen supply checked for the chosen powder
• Cost per part estimated with refresh rate and nesting, not powder price alone

Conclusion

Choosing an SLS material means confirming any certificate the part needs and what your printer can run, then matching the powder to what the part must do in service and checking that choice against cost. For most rigid parts, a general-purpose nylon such as PA12 or PA NEXT is the right starting point. Move to PA NEXT or PA11 when features must flex, to a glass-bead grade when the part must stay stiff or hold its shape under heat, and to TPU when it must be soft.

Four checks prevent most wrong choices. Compare elongation at break, not only tensile strength. Compare HDT values measured at the same test load. Design to Z-direction values when the load runs across the layers. Estimate cost per part with the refresh rate and nesting included, not from the powder price alone.

Some requirements fall outside our current range. PEEK and PEKK process far above the RMS220’s 220°C ceiling, so they need a high-temperature system or a service bureau. Flame-rated and food-contact grades and PP process within that ceiling, so the route for them is a qualified third-party powder or a service bureau.

Datasheet values come from test bars, so the final check is always a printed sample of the real part. We and our resellers run sample prints on customer geometry before any purchase decision. Send us the part, the load case and the finish you need, and we will print it in the two candidate powders.