An Introduction to FFF/FDM Metals 

FFF metals materials

In addition to plastics, some FFF/FDM 3D printers are capable of printing metal filaments providing the extruder is rated for metals, and the nozzle can be upgraded to hardened steel to cope with the abrasive filament.

Metal FFF is based around metal injection moulding (MIM), which uses a three-step process to fabricate metal parts using Bound Powder Filament:

  • Printing: The metal filament is extruded as a metal powder bound in plastic. The print is scaled to account for shrinkage during debinding.
  • Debinding: The printed part is placed in a debinding station, where a solvent slowly melts most of the plastic away.
  • Sintering: The part is placed in a furnace, where the rest of the plastic melts away, and the metal powder solidifies to form a solid part.

The Markforged Metal X leads the field for FFF metal printing, so this article will explore the filaments available for this 3D printer. Generic versions of metal FFF filaments may also be available from other brands.

17-PH stainless steel 

A precipitation-hardened steel that maintains 95% wrought strength at high temps. Good corrosion resistance, widely used for pump shafts and mechanical seals.

A2 and D2 Tool Steel

Cold work steels. A2 is tougher, while D2 is harder but more brittle. Both are widely used to make cutting and forming tools and in applications of high hardness.

H13 Tool Steel

A standard hot work tool steel with high impact strength. Greater resistance to thermal fatigue than A2 and D2, resisting softening above 540°C.

Inconel 625

A nickel-based superalloy that possesses high strength and resistance to elevated temps. Designed for parts in harsh environments, like turbine hardware.


A reddish metal with excellent heat and electrical conductivity. Good machinability and non-magnetic, suitable for heat sinks, shanks, coils, and EDM electrodes.

How the Metal X works

The Metal X prints a bound metal powder filament with a ceramic release material. The ceramic material release layer between the part and supports allows parts to be removed with the light tap of a hammer.

Metal X Gen 2

A part raft is printed under the parts to support them during printing. The Metal X then prints supports and the main part with bound metal filament.

Like all FFF metal 3D printers, the Metal X uses a vacuum-held disposable print sheet to provide an optimal platform for the build. This way, removing the print from the print bed is as simple as releasing the vacuum.

Metal part

Once printed, the part is placed into the Wash-1, a heated debinding system that circulates Opeteon SF-79 to break down the binding material.

Once most of the polymer binder is removed, the part is placed into the Sinter-1, which heats the part to 85% of its melting point. This releases the remaining binder and turns the ceramic support material to dust. The metal powder melts and forms solid.

Once solid, the part can be removed from the raft.

Overall, the Metal X is an incredible 3D printer. Other FFF metal 3D printers follow a similar process, but Markforged is the only brand with an ecosystem for the printer, materials, wash station and sinter furnace. We sell the full package here.