Working with metal in 3D printing often requires considerable safety systems because of the combustibility of most metals. Vendors of larger additive manufacturing systems can build in safety features in their machines to minimize the hazards. But desktop 3D printing vendors had to get creative to bring metal 3D printing to a smaller footprint. They achieve this by using composite metal materials.
Desktop Metal combines metal materials with a binder (often a carbon fiber) and forms this composite into metal rods to ensure safe handling of the metal material. The rods are fed into the desktop printer’s extruder nozzle, which melts the rods to a point where the material can be easily deposited in a layer-by-layer build process.
Once the part is built, it is removed from the build plate and placed in an office-friendly sintering furnace and heated to a temperature less than 1400 C. This sintering process melts the binder. As the binder is removed, the part condenses to a metal density of 99.7%. Various finishing methods include machining or bead blasting to achieve final tolerances.
The other materials Desktop Metal works with include typical existing metal injection molding materials such as steels, aluminum, superalloys, and titanium.
For Markforged, the company combines metal powder with a plastic binder to make the metal safe to handle. The composite material is then heated and extruded through a nozzle and deposited layer by layer to build the desired object. Once built, the part is removed from the build tray and put into a furnace where the plastic binder is burned off. The part solidifies in this sintering process into a dense metal part—up to 99.7% dense.
Markforged offers several material composites. These composites can consist of fiberglass, Kevlar, carbon fiber, and various metal powders including 17-4 stainless steel, tool steels, Inconel, Titanium, and Aluminum. Up to 60% of a metal powder may be substituted with micro strands of carbon fiber bound in plastic.