Metal 3D Printing

In an over $80-trillion global economy, manufacturing is a 16% slice of the pie, totaling $12 trillion. 3D printing accounts for just 0.1% of that slice, with a global spend of $12.6 billion. Yet experts predict that 3D printing will grow at a rate of 17% in the next few years, representing a massive opportunity for 3D printing entrepreneurs.

This article will look at the current state of Metal 3D printing, including which technologies can 3D print metal, which metals are available, and how much it costs.

While there is constant improvement in metal 3D printing technologies, their main applications remain prototypes, jigs, and fixtures, with a comparatively small production of end-use parts.

One area for 3D metal printing to expand its influence is in providing supply chain resilience. This requirement was clearly on display during the height of the COVID-19 pandemic in 2020. At the time, a survey found that 73% of companies experienced supply chain disruptions in their business, while less than half had sufficient backup plans in place to cover those issues. 

Xerox is targeting supply chain needs in aerospace, automotive, and heavy equipment with its ElemX Liquid Metal printers. Based on the Vader Liquid Metal system, these printers use metal wire, often aluminum, rather than powder, and feature a simple interface to enable usage in any company. The Naval Postgraduate School (NPS), one of their clients, deploys Xerox machines to produce parts like LMX turbine compressors and engines. More generally, they test ways the military can become more independent of slow and expensive supply chains.

Beyond supply chain redundancies, other firms are looking to lower costs and increase throughput to make metal 3D printing a viable production technology for end-use parts. One such company is Desktop Metal, a Massachusetts-based company making metal 3D printing systems, related software, and materials. They produce parts for automotive, consumer, heavy industry, and more. One example is a mirror mount that attaches a rear-view mirror to the roll cage on a BMW race car. Desktop Metal aims to develop 3D metal printing into its next phase, what they call “additive manufacturing 2.0.” 

“We’re focused on additive manufacturing 2.0,” says Desktop Metal CPO Arjun Aggarwal. “It’s really all about volume production of end-use parts. We think, at Desktop Metal, that this is what’s going to take additive manufacturing from 0.1% to 1% of the overall manufacturing.” 

Like chemical behemoth BASF, some companies have created metal filaments designed for Fused Filament Fabrication (FFF) printers. With this metal filament, it is possible to manufacture industrial metal parts in an office environment with 3D printers costing around a few thousand dollars.

The FFF process involves extruding filament through a heated nozzle, building objects layer by layer. Metal filament is essentially made up of a thermoplastic, binding polymer which is filled with tiny metal particles. This means that the 3D printed parts are “green” – they are about 80% metal and 20% thermoplastic.

These green parts must go through a debinding process to remove the non-metal material and then through a sintering process to make them fully dense. Such processes require adequate equipment and represent an additional investment cost. Another option is to outsource the debinding and sintering processes, though the tradeoff is lead times.

Similarly and, more rarely, some manufacturers have developed metal resins for a select few stereolithography (SLA) 3D printers. The resins feature a base polymer material that contains metal particles, and thus parts must also go through extensive post-processing like metal FFF printed parts.

While the two technologies above make metal 3D printing more accessible than ever, most other systems exclusively serve industrial applications. The Xerox Liquid Metal system is, for instance, an industrial machine. This printer begins with commodity-priced aluminum wire, which it feeds into a heated ceramic nozzle. An electromagnetic coil sits outside the ceramic nozzle, energized to create a magnetic field, pushing inward on the metal and producing a droplet. The process is similar to the way an inkjet printer uses droplets of ink, only with droplets of liquid aluminum.

On the high-end side, German manufacturer SLM Solutions makes a $500,000+ printer called the SLM 500, famous for producing a titanium Bugatti brake caliper a few years back. In SLM (Selective Laser Melting), a Laser Powder Bed Fusion (L-PBF) technology, a high-power laser melts metal powder selectively, layer by layer. L-BPF is the dominating category of technologies in metal AM, though manufacturers use different, patented names, like EOS with DMLS (Direct Metal Laser Sintering).

Some industrial metal 3D printing technologies do not involve melting. For example, Cold Spray is a solid-state technology that bonds metals by injecting metal powders into a rocket nozzle. This nozzle sends the particles in a high-pressure stream onto the build surface, where the force of impact makes the particles stick.

Another non-melting technology is Metal Binder Jetting, such as in the S-Print designed by German manufacturer ExOne. A recoater lays fresh metal powder on the powder bed, followed by a spreader and compactor. Next, a printhead selectively deposits a binder material based on a digital CAD file. This process repeats, with the build platform lowering each time, until complete. Printed parts are green and must be sintered, and result in 97%+ density.

A final, main technology to discuss is Direct Metal Deposition (DMD), a type of Direct Energy Deposition (DED) technology mainly used to repair metal parts. First, a nozzle creates a melt pool on top of an existing surface. Then, the nozzle deposits powder onto the surface before melting it with a high-power laser.

Stainless steel, namely 316L stainless steel, is a popular material for filament and powder metal 3D printing. It has good corrosion resistance and performance at high and low temperatures, with good ductility and mechanical properties. This metal can serve many usages, from jewelry to engine parts that come into contact with fluids.

Another material option is maraging steel, available as powder or filament. Maraging steel has high strength and hardness, ideal for tools, molds, and channels. It has excellent mechanical properties, a high strength-to-weight ratio, and good wear resistance but comes at a price; maraging steel can be expensive due to high levels of alloying. 

Titanium offers an extremely high strength-to-weight ratio and is, it too, also very expensive. This material presents important use cases in the medical field thanks to its biocompatibility. Hospitals use titanium 3D printing to make custom-fit spinal implants, hip implants, and prostheses.

Aluminum, being lightweight and offering great thermal properties, is ubiquitious in the automotive and aerospace industries.

Papadakis Racing also recently employed inconel powder to create a complex turbo manifold for its GR Supra race car. Inconel is a nickel alloy with high durability and corrosion resistance, commonplace requirements in engine parts and nuclear power systems.

Copper and copper alloys are highly practical in manufacturing. Copper conducts electricity and heat, making it optimal for mechanical and electrical applications, from heat exchangers to wiring. Copper also has natural antimicrobial properties.

One final material to mention is cobalt chrome. Cobalt chrome powder can produce parts that boast good corrosion resistance and mechanical properties that make them ideal for aerospace and medical industries.

Eric Wooldridge, an engineering professor at Somersett Community College in Kentucky, says that low-cost metal AM is the key to advancing the technology. According to Wooldridge, “you don’t get technology revolution from the top-down. Google started with guys in a garage ; eBay started because people had access to a low-cost way to get rid of their junk. And so you don’t get revolutionary ideas through high-end equipment. You get it through low cost and accessibility.”

Indeed, the availability of materials like BASF’s 316L stainless steel metal filament makes it possible for nearly anyone with a 3D printer to experiment with high-grade 3D metal printing. Getting this technology into the hands of more creative minds will only expand its uses.

At the same time, there will continue to be a need for high-end, expensive applications, like Bugatti’s titanium brake caliper or the Naval Postgraduate School’s experiments with Liquid Metal printers to bypass military supply chains. These technologies have the advantage of showing what metal 3D printing can achieve when pushed to its limits. A combination of top-down and bottom-up innovations will likely propel metal 3D printing technology forward.

What is clear is that, in a multitrillion-dollar manufacturing industry, there is plenty of room for metal 3D printing to grow.