All 3D Printable MJF Materials and How to Choose Between Them

Multi jet fusion spreads a thin layer of polymer powder across the build bed, prints a fusing agent where the part should be solid and a detailing agent at the edges, then passes a heat source over the whole layer. The treated powder melts and bonds; the untreated powder stays loose and acts as support. No separate support structure is printed, so a part can sit inside another part in the same build.

That heat cycle is the constraint. Every powder in the machine sees the same peak temperature, so a material only qualifies if it melts in a narrow window, re-crystallizes predictably, and leaves the unfused powder reusable. Powders that fail any of those three tests stay out of the qualified list, no matter how good their datasheet looks in isolation.

The practical result is a short list. A handful of polyamide grades and one elastomer cover most production work. Everything else on the market is either a variant of those grades or a niche powder with a narrow supplier base.

PA12 is the default. It has the widest processing window, the best dimensional consistency across a build, and the lowest cost per part of any MJF powder. Parts come out a matte gray with a slightly grainy surface, and they hold up to repeated handling without chipping. For brackets, housings, ducts, and fixtures, this is where most projects start and stop.

PA11 costs more and prints softer. It has better impact resistance at low temperature and higher elongation before break, which matters for living hinges, snap fits that will be cycled, and parts that see vibration in service. It also takes impact modifiers more readily than PA12, so blends with improved toughness are available.

Glass bead filled PA12 raises stiffness and reduces creep under sustained load. The trade is surface finish and elongation: the beads make the surface rougher and the part more brittle, so it is a poor choice for snap fits and good for structural brackets, jigs, and anything that will sit under a static load for months.

Thermoplastic polyurethane covers the flexible end of the range. It prints as a rubbery part with usable rebound, which suits gaskets, grips, seals, and vibration dampers. Thin walls in TPU can curl during cooling, so wall thickness and part orientation matter more here than with any rigid powder.

PA6 and glass filled PA6 appear in some machine ecosystems. They offer higher temperature resistance and better mechanical strength than PA12, at the cost of a narrower processing window and higher powder price. Check machine and material compatibility before you design around them, because support varies by supplier and region.

Minimum wall thickness sits around 0.8 mm for rigid powders and 1.5 mm for TPU. Below that, the fusing agent does not have enough material to bond across the layer, and the wall comes out porous or warped. If a design calls for 0.5 mm fins, MJF will not deliver them reliably.

Holes and slots smaller than about 1 mm tend to close or fill with semi-fused powder. Design them at 1.5 mm and up where the function allows, and plan on drilling or reaming critical bores afterward. MJF is not a precision boring process.

Dimensional tolerance lands around ±0.3% of the dimension, or ±0.3 mm, whichever is larger. Long thin parts warp more than compact ones because the cooling gradient runs along the length. Adding ribs or a uniform wall section helps more than tightening the tolerance callout.

Sharp internal corners concentrate stress and cool unevenly. A 0.5 mm fillet at the base of a rib costs nothing in the design and removes a common failure point on the printed part.

MJF wins when the part is organic in shape, has internal channels or undercuts, and will be produced in tens to thousands of units. It loses when the part needs a tight tolerance, a smooth sealing surface, or a metal substrate.

A face that must seal against an O-ring, a bore that takes a press-fit bearing, or a thread that will be assembled and disassembled repeatedly all need machining. Printing the shape and cutting only the critical features is often the cheapest route: the MJF body carries the complex geometry, and a CNC operation brings the sealing face to ±0.005 mm and Ra 0.8–1.6 μm.

Metal parts stay in metal. If the application needs stiffness above what glass-filled PA12 provides, thermal conductivity, or electrical grounding, no MJF powder will substitute. Aluminum 6061 or 7075 machined on a 5-axis center covers those cases, and we run both processes side by side.

Volume changes the math too. Below roughly 50 units, MJF usually beats injection molding on cost because there is no tool to amortize. Above a few thousand units with a stable design, molding takes over. In between, the answer depends on how likely the design is to change.

As-built MJF parts come out gray with a pebbled texture. Bead blasting evens the surface and removes loose powder from fine features. Tumbling smooths edges on small parts but can round sharp detail, so mask or protect anything dimensionally critical.

Dyeing gives a uniform black or colored finish that penetrates the surface. It does not fill pores or change dimensions meaningfully, which makes it a common choice for visible covers and enclosures.

For parts that need a sealed or low-friction surface, machining the functional faces after printing is more reliable than any coating. We machine MJF bodies on the same 3-axis and 5-axis centers we use for metal, which keeps the printed and cut features in one coordinate system.

If a printed prototype later moves to metal production, the transition is easier when the critical features were already machined. The CAD is set up once, and only the body process changes.