Mark Barfoot Mark Barfoot
President

Wire-Directed Energy Deposition Technology

August 10, 2020


Wire directed energy deposition (wire-DED) additive manufacturing (AM) technology employs metallic wire as the feed stock, and either an electric arc, laser or electron beam as the energy source. Each type of heat source creates its own, unique AM process—arc DED, laser-wire DED and electron-beam DED. However, each of these processes shares a common feature: the melting of a continuously fed metal wire by the energy source, to deposit molten metal along a predetermined path.


Fig. 1—A mixed-material wire-DED system at the Cranfield University in United Kingdom produced this part from steel and bronze.
First patented in 1920, wire-DED technology probably is the oldest, outwardly simplest, but least-talked-about AM process. Using wire as feedstock, the basic process has been used for decades to perform local repairs on damaged or worn components, and to manufacture round components and pressure vessels. More recently, the advent of computer-aided design and manufacturing (CAD/CAM) software has made AM a cost-effective and viable process, with wire DED being an area of significant development. The process has gained momentum in major sectors including aerospace, nuclear and tooling, due to its potential to produce large-scale components with higher build rates compared to powder-based AM systems.

The advantages of wire DED include simplicity, flexibility, high deposition rates and the ability to fabricate large-scale parts with high structural integrity. The process can greatly reduce manufacturing cost, as well as the buy-to-fly ratio. Research has demonstrated that this technology can reduce costs by more than 60 percent, while reducing waste material by 90 percent as compared to traditional subtractive processes. Research also shows that this technology, combined with conventional machining, can significantly decrease cost and lead time.

Powder vs. Wire

Compared with powder-based AM systems, the hardware costs of wire-DED systems are much lower. Shops can assemble a wire-DED setup by combining a common motion platform based on industrial robotic arms or a gantry, along with commercial wire-based welding equipment, or by refitting existing welding machines.

Furthermore, wire as a feedstock provides quality and safety advantages compared to metal powder. Due to their high surface area, metal powders are especially sensitive to their environment and prone to absorb moisture, oxygen and other elements present in the air, affecting printability and the final material properties of the printed parts. Metal powder also poses safety risks due to the potential for flammability and inhalation. Wire DED does not pose these concerns.


Fig. 2—A distorted wall fabricated using wire-arc DED.
Technically, the wire-DED process can print with any weldable materials, including mild and high-strength steels, stainless steel, aluminum alloys (Type 4043 and 6082), titanium alloys (Ti-6Al-4V), and copper alloys, as well as refractories. In addition, the technology supports mixed-material use, so that shops can produce parts by using multiple materials (Fig. 1).

Hidden Complexities

Robotic-arm speed/gantry-head speed, wire-feed rate, nominal thermal conditions, wall structure and the average layer height represent the basic building blocks of printing arbitrary shapes using wire DED. Most components will have relatively simple geometries, but geometrical accuracy might not be as high as with other AM technologies, such as with powder-bed fusion, since wire DED uses an extremely high-temperature heat source. The relatively high heat input can cause high residual stress and distortion (Fig. 2) and negatively affect geometrical accuracy through plastic deformation. It also can dramatically affect the mechanical properties and performance of the printed components, including reduced fatigue life and tensile strength.

As of 2020, the wire-DED market remains small, with a handful of companies actively developing the technology. These include WAAM3D, Lincoln Additive Solutions, GKN Aerospace, Sciaky, AddiTec, Gefertec and MX3D AML3D. While it may take time for applications to develop and the benefits to be felt throughout the industry, we do see a growing demand for large, metal 3D-printed components, suggesting that the adoption of wire DED will accelerate.

Ultimately, wire DED will transform the way that large metal parts are produced, giving companies the option of a fast and cost-effective production method. 3DMP

Industry-Related Terms: Additive manufacturing, Directed energy deposition, Layer height, Metal powder, Residual stress
View Glossary of 3D Metal Printing Terms

 

See also: EWI

Technologies: Directed-Energy Systems

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