Unraveling WAAM: Your Complete Guide to Metal 3D Printing

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Wire Arc Additive Manufacturing (WAAM) is a sub-category of Directed Energy Deposition (DED) 3D printing. DED is a metal 3D printing method which uses a nozzle mounted on a multi-axis arm to deposit metal material in either powder or wire form. This material is then melted by a focused energy source, such as a laser, electron beam or plasma, to construct the object layer by layer. WAAM uses an electric arc as the heat source, a concept derived from arc-welding.

Automated welding techniques using robotic systems form the basis of WAAM technology. These include metal-inert gas (MIG) or metal-active gas (MAG), tungsten-inert gas (TIG) or plasma arc-wire (PAW). Additionally, the Cold Metal Transfer (CMT) welding process, a derivative of MIG which was developed by Fronius in 2004, is frequently utilised. WAAM is compatible with various metals such as titanium, aluminum, nickel, and steel alloys, among others.

Applications for WAAM 3D Printing

DED processes like WAAM are commonly used for equipment repairs and parts reproduction, particularly for maintaining vintage machines or manufacturing obsolete parts. Notably, this technology has applications in creating complete components and is particularly useful in industries such as aerospace, automotive, defense, and energy. It’s widely employed for the production of prototypes, molds, singular parts, and small series. Although the utilization of WAAM in mass production is still scrutinized, it’s uniquely apt for crafting large, metal components.

To illustrate its versatility, Naval Group has leveraged WAAM technology within the aerospace industry by manufacturing a propeller for the mine-hunting vessel Andromède. Similarly, in the energy sector, Vallourec has fabricated the first sealing ring using WAAM technology to bolster the safety of EDF Hydro’s hydroelectric facilities—a weighty element of 100 kg and a diameter of a meter. Furthermore, the robotics industry has seen applications of this technology, with MX3D employing it to produce a structural steel connector. MX3D further makes use of WAAM to fabricate pipe connectors for the oil and gas industry, along with gears and distinct components for large-scale machinery. One notable achievement by MX3D includes the construction of a bridge in Amsterdam using the WAAM method. Adding to its impressive portfolio, Relativity Space leveraged this technology to engineer its Terran 1 light launcher. Lastly, it’s common to see the use of WAAM in the production of molds in the plastic industry.

WAAM 3D printing brings a myriad of benefits to the table. Its high printing speeds shorten production times, and the costs tend to be more economical compared to machines employing powder-bed fusion technology, specifically Selective Laser Melting (SLM). Another key feature of WAAM technology is its competency in the production of incredibly large parts. Additionally, it boasts impressive compatibility with a broad spectrum of metallic materials.

Limitations of the Technology

The WAAM process also has its limitations. Since it allows faster printing, the detail and dimensional accuracy of the parts are less well reproduced than with powder-bed fusion technologies. Parts manufactured using WAAM technology can have defects such as internal porosities, which can degrade the mechanical properties of the part, either statically or in fatigue when the part is subjected to various forces, resulting in damage. This is particularly true of aluminum parts.

Residual stresses are another anomaly that can occur with WAAM technology. They can lead to deformation of the part’s dimensions and/or shape, notably through curling, warping, or delamination. All these phenomena are characterized by deformation on the layers of the printed part, be it the top, bottom or, in the case of delamination, all the layers. These deformations are caused by the very high working temperature and the technical nature of the materials. They will result in the part holding up poorly when forces are exerted on it.

Vallourec uses WAAM technology for power plants (photo credits: Vallourec)

To limit the occurrence of these defects, it is necessary to understand all the WAAM parameters to set them accurately. This will ensure a consistent molten metal deposit and constant heat. Parameters like unwinding speed, feed speed, current, voltage, layer thickness, protective gas flow rate, and bead spacing all contribute to a smooth process.

There are also technical solutions to mitigate these anomalies. These include mechanical work-hardening, or rolling. This method involves exerting pressure on the weld bead with a roller during the cooling phase, which reduces porosity. For reducing residual stresses, the material can be preheated. It’s important to note that some materials and alloys are more susceptible to cracking or delamination than others, e.g. aluminum-copper, aluminum-titanium, and aluminum-iron alloys.

Like other additive manufacturing technologies, a considerable amount of finishing post-processing is required. Post-processing is typically done using a traditional machining process. In some WAAM applications, machining can be done during the printing phase by using a second robot.

WAAM 3D Printer Manufacturers

An MX3D 3D printer using WAAM technology (photo credits: MX3D)

Manufacturers of 3D printers using WAAM technology include Prodways, whose 3D printers work with the WAAM-TIG process, Norsk Titanium and its in-house Rapid Plasma Deposition (RPD™) process, GEFERTEC, MX3D, WAAM3D and Lincoln Electric, among others.

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