Mark Barfoot Mark Barfoot
Director of AM Programs

Shining the Spotlight on Laser-Powder DED

May 14, 2020


Laser powder-bed fusion (L-PBF) is the most prevalent metal-based additive manufacturing (AM) technology. Binder jet and extrusion-based binder jet systems also have gained plenty of attention, with recent entrants from several companies including HP, Desktop Metal and Markforged. A newer metal-AM technology that has not received much media buzz—but should—is directed energy deposition (DED).

Sandia National Labs introduced the DED process in 1997, and Optomec commercialized the technology shortly thereafter with its Laser Engineered Net Shaping (LENS) system. Other companies and universities around the globe have developed variations of the DED process, including one introduced more a decade ago by National Research Council Canada called laser consolidation (LC). Burloak Technologies, Oakville, Ontario, Canada, licensed the LC DED process in 2019. Other examples of DED metal-AM technology include BeAM, which started producing machines in 2012 in France, RPM Innovations and Formalloy. We also spied several other DED-based systems at the 2019 formnext tradeshow in Germany.

In the last five years, hybrid systems that combine DED technology with CNC machining have emerged, from suppliers such as DMG Mori and Mazak. This advancement has helped bring DED to the forefront, but shops still have been slow to adopt it in production.

The Benefits of Laser-Powder DED
Rotating the part under a laser-powder DED feed head avoids the need to add support material during the metal-AM process.

During the laser-powder DED process, metal powder feeds through tubes for injection into the focused beam of a high-power laser. The DED head mounts onto a gantry or robot, which then moves around the build area to deposit layers of molten metal. The technology has the unique advantage of not requiring an actual bed of powder; it only needs powder in the spray area of the build. Most of the material ends up in the final part, with typically less than 20-percent overspray during builds.

Without requiring a powder bed, DED technology is readily scalable, as most machines can produce parts several cubic feet in size, compared to the typical L-PBF work envelope of less than 1 ft.3. In addition, the DED process does not require support material. By rotating the part relative to the deposition head, many designs that typically would require support material with a powder-bed process can be built vertically without additional support structures.

Laser-powder DED processing also produces highly finished surfaces, similar to the finish quality of AM parts made using L-PBF. In contrast, wire-based DED systems typically produce near-net shapes with very rough layer lines, which usually require post-machining.

Adding Features to Existing Parts

Although laser-powder DED machines can build off of a standard baseplate, build plates are not required. Shops can place existing parts, or standard shapes such as cylinders, in a DED machine and then use the AM process to add features to their geometry. This allows for fast fabrication of components with large cross-sectional center cores. Here, the center is fabricated using conventional methods from a standard, off-the-shelf material, and then DED technology adds the more challenging features—perhaps with a different material—to that simple core.  

Recent developments with DED systems have involved building parts using multiple materials fed through the single feed head. This technique allows an AM shop to vary the percentage of each material deposited into each layer or portion of the part. It also enables efficient building of parts comprising graduated material properties. For example, a shop can build the inner core of a part from a highly wear-resistant material such as Inconel, to withstand abrasive wear from flow through the part, and then deposit a corrosion-resistant top layer of stainless steel. Again, the lack of a powder bed allows for simple adjustment of the materials being deposited into specific layers.

(Note: Formalloy recently introduced, at Rapid + TCT 2019, its Alloy Development Feeder, which enables rapid deposition of as many as 15 different alloys or alloy blends. It features a revolver-style motion that lets the user select the gradient mixture for each specific layer.)

Applications

Many companies look to DED to produce parts from expensive materials, as the process greatly reduces or eliminates waste. The process also finds favor in producing parts from materials that prove difficult or impossible to machine.

Other applications involve repair of parts worn or damaged in service—turbine blades, for example. The ability to repair worn or broken parts using DED greatly reduces equipment downtime. The repair or maintenance shop places the damaged part into the DED system and deposits the material required for the repair. DED also plays a role in mold and tooling applications, used to repair or add tough wear-resistant material to cutting edges or fragile features. 

Adoption Challenges

Why doesn’t DED find more widespread use? Machine cost for starters, as the systems are expensive and require large facility space. Most systems also require an inert environment, and can consume significant amounts of argon to evacuate the process chambers. 

However, the biggest challenge with the technology relates to programming, as DED often requires moving the deposition head in precise, five-axis motion to build up part features. Only recently have we seen the improvement of software tools that allow for simplified programming. However, DED machines still can prove more challenging to program than plastic-AM systems or even L-PBF machines. As the adoption of DED grows, we expect to see continued advancements in software to allow for even quicker, more seamless programming of builds.

As EWI continues to work with companies adopting DED, I’m excited to see the applications developing. And, I’m equally amazed at the many companies that haven’t yet looked at DED. There are many industries for which the technology can be a fit. I encourage manufacturers to do some research and seek out a partner to help determine if DED may fit their applications.  3DMP

Industry-Related Terms: Abrasive, Alloys, Bed, Center, CNC, Core, LASER, Layer, Lines, Overspray, Stainless Steel
View Glossary of Metalforming Terms

 

See also: EWI, Buffalo Manufacturing Works

Technologies:

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