3D metal printers propel additive manufacturing (AM) to the cusp of a new era. The latest models allow unprecedented geometrical complexity and advanced alloys, allowing designers and engineers to aim for the sky. And there is nothing wrong with hitting an airplane, satellite, or lunar base in the process, because those are prime applications.
Here is an overview of the astronomical impact they will have on the world of 3D printing.
Fine Technology
Let’s stop using metaphors and dig straight into the topic. Metal 3D printing is still a young sprout in the field. In 1987, the first stereolithography (SLA) 3D printers were commercialized, and two years later came fused deposition modeling (FDM). These work with resins and plastics, respectively, and FDM branched out into the widely known fused filament fabrication (FFF) that extrudes filament instead of powder.
The first metal 3D printer launched in 1994 with the EOSINT M250. It sinters a blend of two metal powders, one of which with a low melting point for constituting a binding matrix, into freeform solid shapes. A decade later, the M270 was the first fully dense metal printer in a process known as DMLS. So what are the available techniques today?
Powder Bed Fusion (PBF)
A laser fuses powder contained in a bed layer by layer, much like selective laser sintering (SLS) does for plastics. It is slow and thermal gradients during the print require some technical expertise, but without support structures any geometry can be established. It works with steels, titanium, nickel alloys, cobalt-chrome, and aluminum. Subvarieties include:
- Direct metal laser sintering (DMLS).
- Selective laser melting (SLM) also known as direct metal laser melting (DMLM).
Binder Jetting (BJT)
This is a rapid process where layers of deposited powder are glued together using a binder, which is sintered out in a later stage. A lower melting temperature metal is wicked into the part to obtain full density. It works with steels, bronze, and tungsten. Variants include:
- Rapidia machines use a water-based metal paste so no debinding is required.
- In material jetting, instead of a binder, nanoscale metal particles are directly jetted to construct the part for ultra-high resolution.
Directed Energy Deposition (DED)
In this up-and-coming process, filament is extruded into a melt pool produced by a laser or plasma arc. It’s a fast process that produces near-shape parts to be finished by CNC milling. Limited geometry can be realized in steels, titanium and nickel alloys, and tantalum. Varieties include:
- Wire-arc additive manufacturing (WAAM) performed cost-effectively by GMAW (welding) robots.
- Electron beam freeform fabrication (EBF3) developed by NASA has a dual wire feed and focused electron beams for titanium, aluminum, and Inconel.
Direct Metal Deposition (DMD)
Instead of strands of filament, a powder is extruded into the melt pool, much like FDM for plastics. It can be used for repairs and is also known as laser metal deposition (LMD).
Ultrasonic Additive Manufacturing (UAM)
A form of sheet metal lamination where sheets are cut out and stacked on top of each other to subsequently be bonded by ultrasonic vibration. This allows multi-metal structures and placement of inserts during the printing process. Comparable with laminated object manufacturing (LOM).
Atomic Diffusion Additive Manufacturing (ADAM)
A metal-filled plastic filament is extruded, then the polymer is dissolved using a chemical process and parts are furnace-sintered. An easy-to-remove support structure somewhat limits freedom of design. Works with steels, Inconel, copper, and titanium. Also known as bound metal deposition (BDM).
Fused Filament Fabrication (FFF)
Conventional 3D printers can be outfitted with hardened nozzles for printing plastic-metal composites, mostly for decorative items. Research is being done into low-melt temperature materials such as solders.
Lost-Wax Casting
Wax objects are printed through stereolithography, then used as master molds for an investment casting process of brass, copper, gold, silver, and other precious metals.
The Future of Manufacturing
Metal AM is undeniably fundamental for the digitized “smart” factories of the future. Granted, it requires a lot of post-processing work and expertise, but with automation plus decreasing cycle times and feedstock prices, it can become one of the mainstream alternatives to die-based processes like metal injection molding, hydroforming, and press molding.
Complex geometries can, through generative design software, artificial intelligence, or cloud applications for Grasshopper, be realized, such as optimal structures for bicycles, skateboard trucks, robot bodies, life-saving drones, and architectural space frames.
Honeycomb lattices make way for organic gyroids to further lightweight and strengthen large structures, while ordered-cell metal foams improve heat exchange and energy absorption systems. This leads 3D printing into its promised industrial bloom and renders it imperative that today’s children learn to 3D model and code at a young age.
Open Fields
With 3D printing expanding from plastics into new materials such as composites, concrete, ceramics, silicones, glass, and metal, complete engineering prototypes or even end products will be fully 3D printable across a span of industries. This drastically simplifies the supply chain network and accelerates product development. And it can reduce the weight of assembly parts by as much as 50%, as exemplified by turbines and impellers produced by Airbus and Boeing.
In terms of quality, sintered and heat-treated additive products can be stronger and more wear-resistant than their wrought counterparts, making superior drill bits and other parts possible for the mining and oil and gas industries.
A 3D printed engine piston proved mechanically equivalent yet more lightweight, causing it to power up the Porsche 911 GT2 RS by 30 hp. What’s more, end-of-life or obsolete parts can be turned into reusable powder, potentially turning firearms into something more creative and beneficial.
In manufacturing plants, AM can produce extrusion dies, molds for injection molding, and sheet metal embossers, saving time and waste material compared to CNC machining. It will be possible to print mechanical parts such as gears, valves, nozzles, fasteners, and mounting brackets while changing dimensions and design features as required from item to item.
Volkswagen has already achieved efficiency gains using 3D printers that create assembly jigs and fixtures based on the workfloor’s demand. Mercedes and Deutsche Bahn use them to produce critical spare parts for older machinery, preventing downtime.
Metal 3D printing currently finds most of its impact in medical applications. Titanium skull, jaw and other implants as well as hip and knee replacements are biocompatible, lightweight, and bulletproof. Surgeons are empowered to create their own tools and rapidly iterate on existing designs for advanced operations. Dental crowns and bridges become almost ready-while-you-wait.
One of the most noticeable outlets of metal 3D prints is aerospace. Entire heat shields and command-and-service modules 6 meters in diameter can be 3D printed using the EBF3 process. And SLM turns out ideal for smaller components in advanced alloys.
When deployed as part of in-space manufacturing (ISM), 3D metal printers will produce spare engineering-grade parts and tools for astronauts on long missions. Advanced heat exchangers that convert Martian air into air breathable by humans are currently being researched as well. Metal 3D printing can tackle almost any manufacturing challenge in any field.
Layer-by-Layer Democratization
Where the mainstream market for desktop plastic fabricators got saturated in a decade, this will take significantly longer for their metal-melting brothers and sisters. But the first steps are being taken to transport the industry into classrooms and living rooms.
With filament-based raw material, spacious build envelopes, and a price under $100k, Markforged, Additec, and Desktop Metal are making their high-tech somewhat accessible. A simpler version is already offered by Iro3d, the price tag on par with the first desktop SLS systems.
When barriers to entry are relieved, powder-based methods may prove to be the best mainstream process because of their great finish, limitless design possibilities, and strength. A world where people produce their own bike frames, door handles, faucets, fashion accessories, golf clubs, and jewelry may not be far off, permanently shifting demand from products to intelligent software systems and services.
