SLS 3D Printing — PA12 (Nylon 12)

What is PA12 (Nylon 12) and why is it the SLS default?

PA12 is a semi-crystalline polyamide supplied as a fine powder (~50–60 µm particles). In selective laser sintering, a CO₂ or fiber laser fuses each layer inside a heated powder bed held just below the polymer’s melting point, so the surrounding loose powder supports the part — there are no support structures to remove and no anisotropy penalty from a build plate. PA12 became the industry default because it has a wide, forgiving sintering window, recycles reasonably between builds, and lands in a sweet spot of strength, toughness, chemical resistance and detail that covers most functional-part jobs.

Because the powder bed carries the load, SLS prints geometry that FDM and SLA struggle with: internal channels, conformal lattices and captive assemblies in a single job, with no support scars. That is the structural reason PA12 dominates functional and small-to-mid-batch production. For the full process and machine context, see our SLS 3D printing overview.

PA12 material properties (typical SLS values)

The numbers below are representative for laser-sintered PA12 in the as-printed (untreated) state. Exact figures vary by powder brand, refresh ratio and machine, but the ranges are stable enough to design against.

Values are typical engineering ranges for laser-sintered PA12, as-printed. Always confirm against the specific powder’s datasheet for a regulated or load-bearing application.

What are PA12’s strengths?

• Near-isotropic strength. Unlike FDM, a PA12 part is roughly as strong pulled along Z as along X/Y — you design for one strength number, not a weak layer plane.
• No supports, complex geometry for free. Loose powder holds the part, so lattices, internal ducts, captive hinges and nested assemblies print in one job with no support removal.
• Tough and functional. ~11% elongation means snap-fits, clips and press-fits survive real assembly cycles instead of cracking like resin.
• Chemically robust. Shrugs off fuels, oils, greases and many solvents — good for under-hood, fluid-handling and industrial parts.
• Stable and repeatable. A well-characterized powder gives consistent dimensions build-to-build — what makes small-batch end-use production viable.
• Finishes and dyes well. The porous matte surface takes bead-blasting, tumbling, vapor smoothing and immersion dyeing — most commonly a deep black.

What are PA12’s limits?

Honest constraints we see on the shop floor:

• Porosity. As-printed PA12 is ~3–8% porous, so it is not airtight or fully watertight without post-processing (vapor smoothing, sealing or infiltration).
• Moisture uptake. Like all nylons it absorbs ambient water, which slightly shifts dimensions and toughness; condition parts for tight-tolerance metrology.
• Heat under load. Fine for ~80–90 °C service, but it softens well below its melt point when mechanically loaded — for hot structural parts step up to PA-CF.
• Matte, grainy surface. Excellent for engineering, but not the glass-smooth cosmetic finish of SLA resin without extra finishing.
• UV and long-term color. Natural PA12 yellows in sun over time; dyeing black and a UV-resistant coat help outdoor parts.
• Stiffness ceiling. At ~1.7 GPa it is stiff but not rigid — thin unsupported spans flex. Carbon-filled nylon is the fix.

What is PA12 best used for?

PA12 is the right first choice whenever you need a real functional part rather than a look-and-feel model. Typical jobs we print:

• Enclosures and housings for electronics and instruments, with integrated bosses, ribs and snap-fit lids.
• Ducts, manifolds and fluid channels with smooth internal curves impossible to mold or machine cheaply.
• Brackets, mounts and clips — lightweight, vibration-tolerant structural hardware.
• Snap-fits and repeated-flex features (PA12 handles many snap cycles; for true living hinges, PA11 is better).
• Jigs, fixtures and manufacturing aids that must survive a shop environment.
• End-use production parts in small-to-mid batches — drones, automotive, robotics, medical devices (biocompatible grades), spare parts on demand.

Finishing and black dyeing PA12

PA12 leaves the printer a pale grey-white with a uniform matte texture. Because the surface is microporous, it is one of the easiest 3D-printing materials to post-process:

• Bead blasting — standard first pass; removes loose powder and evens the finish.
• Tumbling / vibratory polishing — knocks down edges and smooths for a more uniform feel on batches.
• Vapor smoothing — chemically melts the outer skin to a sealed, semi-gloss surface; this is what makes PA12 effectively watertight and far easier to clean.
• Dyeing — parts are immersed in a hot dye bath. Black is by far the most common: the porous nylon absorbs dye into the surface (not just a coating), giving a consistent, robust deep-black color that won’t chip like paint. Other colors are possible, but black is the production standard.
• Coating / sealing — optional for UV resistance, extra wear resistance or a specific gloss level.

One practical note from our shop: dye penetrates only a fraction of a millimeter, so heavily abraded areas can show lighter. For cosmetic black parts, vapor-smooth first, then dye.

PA12 vs PA11 vs PA-CF: which nylon should you pick?

All three are SLS nylons printed support-free, but they trade off ductility, stiffness and temperature differently. Quick rule: PA12 for general-purpose functional parts, PA11 when you need toughness and flex (impact, living hinges), PA-CF (carbon-filled Nylon 11/12) when you need stiffness and heat.

In practice, most jobs that land on our SLS line stay on PA12 — it is the cheapest of the three, the best characterized, and strong enough. Move to PA11 only when a part must flex repeatedly or take impact (a clip that snaps thousands of times, a thin living hinge). Move to PA-CF (carbon-filled nylon) when stiffness or heat is the limiting factor and you can accept a rougher, abrasive-to-handle surface and lower ductility. For a deeper side-by-side with test numbers, see PA12 vs PA-CF.

How much does PA12 SLS cost?

SLS pricing is driven mostly by the powder a part consumes and how densely the build chamber packs (nesting), not by part complexity — geometry that costs money in FDM supports or CNC time is essentially free in SLS. So small, dense, nestable parts in a full build are the most economical, and internal features cost no extra. The honest trade-off versus FDM: PA12 has a higher entry cost for a one-off, but wins on functional quality, isotropy and per-part cost once you are printing a batch. For a firm number, send the model — packing density and wall thickness move price more than any rule of thumb.

Bottom line: how to choose

If you need a functional plastic part and you are not sure which material to start with, start with PA12. It gives you near-isotropic ~48–50 MPa strength, ~11% elongation, good chemical resistance, no support structures, and a finish that dyes cleanly to black — covering housings, ducts, brackets, snap-fits and genuine end-use production. Step up to PA11 only for impact and living hinges, and to PA-CF only when you need stiffness or heat and can accept a coarser surface. For the broader process picture, read our SLS 3D printing overview; to compare the carbon-filled option directly, see PA12 vs PA-CF.

We have run SLS PA12 in-house in Kyiv since 2015, across 12,000+ orders — from single prototypes to repeat production batches, with finishing and black dyeing done on site. If you have a model, send it over and we will print a test part, measure the features that matter, and quote the batch.