Microwaving metal with The Virtual Foundry

To help spur the introduction of metal 3D printing, metal filament manufacturer The Virtual Foundry introduced a new method of debinding and sintering printed components – with a microwave.

Still in a developmental stage, Virtual Foundry's Metal Microwave Sintering technology is among the first of its kind involving the use of a commercial microwave instead of a kiln or furnace to heat prints inside of a crucible.

Though only tested on the company's own Aluminum 6061 Filamet 3D printing material, the company believes the process could soon offer manufacturers a faster and lower cost means of debinding and sintering metal parts.

Debinding is the process that removes the primary binding material from the molded component, commonly a type of wax, to help glue the layers together during printing. This process is completed prior to sintering, which uses pressure or heat to form a solid mass of material without melting it to the point of liquefication.

"Since the beginning, our quest has been to democratize metal 3D printing," said Virtual Foundry CEO Bradley Woods. "The advent of a microwave sintering process for metal 3D prints is a tremendous shift in the momentum of this movement."

Accessible metal 3D printing

Established to make metal 3D printing more accessible, The Virtual Foundry was one of the first to bring workable alloys to the fused filament fabrication space with its Filamet 3D printing materials. Each of these can be printed using any available material FFF system into alloy-infused parts, which can then be post-processed into fully-dense metal objects using a kiln.

Virtual Foundry's Filamet range includes everything from copper to iron to Stainless Steel 316L and Inconel 718 materials, all of which can be sintered at high density.

Elsewhere in its portfolio, the company also markets The Virtual Foundry Metal 3D printer and three Virtual Foundry Sintering Kilns, but in keeping with its accessibility philosophy, its materials can be used with most debinding and sintering equipment as well.

In practice, the firm has worked with the likes of NASA, Mitsubishi, and the U.S. Department of Energy to drive the application of its technologies, which continues to gain traction in the automotive, aerospace, military, and education sectors.

The company is also working to build out its material portfolio, launching Rapid 3DShield Tungsten earlier this year – a tungsten-based radiation shielding filament.

Likewise, The Virtual Foundry recently introduced an FFF Metal 3D Printing Evaluation Kit, which has everything a newcomer to the world of metal 3D printers needs to produce samples before sending them back to the company for sintering and shipping.

Microwaving metal?

Metal 3D-printed parts that are reinforced with a binder must go through a debinding and sintering process before they are ready for end use. Presently, this tends to involve burying prints inside a refractory ballast in a crucible, which is then placed inside a furnace or kiln and heated until the binder is burnt off – hence, debinding.

Though conventional workflows enable the post-processing of metal 3D printed parts with a high degree of repeatability, Virtual Foundry has now begun developing a new, more accessible approach.

Instead of relying on a kiln, the company's technique involves inserting parts enclosed within a heating element-loaded crucible into a microwave.

How is this possible?

Made from a standard refractory material lined with silicon carbide, these "microwave kilns" are designed to act like the cardboard sleeve around a Hot Pocket. This essentially traps the waves of a microwave back into the subject being heated, thus not having the feedback into the device itself and causing an explosion at best.

Once users have calibrated their microwave, The Virtual Foundry says they can then deploy it to heat up their crucible, and its silicon carbide content will effectively concentrate energy on the parts inside.

Thoroughly reviewed by YouTube tinkerer "Highball," who managed to benchmark a 600-watt microwave and use the technique to post-process aluminum parts with varying degrees of success, he says that the product still has some "serious hot spots" that remain to be addressed.

Additionally, Highball's successful processing of aluminum is significant as the alloy traditionally requires the use of sintering carbon or the input of certain gasses during sintering due to its reactivity with oxygen.

With further research and development, the YouTube engineer says microwave sintering could be used to process other challenging reactive alloys, such as titanium, without needing to account for oxidization.

Hopefully, with further refinement, accessibility to metal 3D printing will become nearly household, as practically every home has a microwave. And even if some or most do not, even with the necessity of a commercial microwave currently, if the technology becomes more developed, the options to debind and sinter metal components will be as easy as visiting the nearest appliance store.