Wire and Arc Additive Manufacturing (WAAM) is revolutionising the production of significant, complex components, particularly in the marine and aerospace industries. Unlike traditional 3D printing methods, WAAM uses fusion welding to build metal parts layer by layer, creating durable, custom components on demand. This case study highlights WAAM's successful applications in producing marine propellers and aircraft structures, demonstrating its efficiency, cost-effectiveness, and ability to deliver large-scale components.
Projects such as producing the world's first class-approved marine propeller and advancements in airframe component fabrication demonstrate the technology's impact. However, WAAM also presents challenges, particularly in preventing oxidation during welding. Innovative solutions like Flexible Welding Enclosures® and PurgEye® Weld Purge Monitors® ensure the integrity of WAAM-produced parts by providing controlled environments and precise oxygen level monitoring. As WAAM continues to evolve, it is set to play a crucial role in the future of manufacturing for critical industries.
The Rise of WAAM Technology
Since the introduction of 3D printing over 30 years ago, the technology has evolved significantly, leading to various methods for creating complex structures. Wire and Arc Additive Manufacturing (WAAM) has emerged as an up-and-coming technique for producing significant, intricate components like marine propellers and aircraft structures. Unlike traditional 3D printing, which often relies on delicate powder-based processes, WAAM utilises fusion welding to deposit metal layer by layer under computer control, creating durable, custom parts on demand.
WAAM technology has revolutionised manufacturing by eliminating the need to maintain an inventory of high-value generic stock, allowing parts to be customised and produced as needed. This has opened up new opportunities across various industries, particularly in marine and aerospace applications. Two notable examples of WAAM's impact are the production of ship propellers and the fabrication of airframe components.
Marine Propellers:
The Damen Shipyards Group collaborated with RAMLAB, Promarin, Autodesk, and Bureau Veritas to develop the world’s first-class-approved marine propellers using WAAM technology. This project, initiated by a research program involving students from Delft Technical University, culminated in the production of a 1300mm diameter bronze propeller for a Damen Stan Tug type 1606 (Fig 1). The propeller, weighing approximately 180kg, was fabricated using the GTAW (TIG) process, demonstrating the cost-effectiveness and efficiency of WAAM in producing large-scale maritime components.
Aircraft Structures:
Researchers at Cranfield University in the UK have advanced WAAM technology for fabricating airframe components from materials such as Inconel, titanium, aluminium, and various nickel alloys. Unlike laser and powder methods, which are limited by their speed and the size of components they can produce, WAAM is designed for high deposition rates. Cranfield’s program, which began in 2007, targets a deposition rate of 10kg per hour for titanium, compared to the typical 0.1kg per hour achievable with laser and powder methods. WAAM systems can also produce parts several meters in size, simplifying the production of single-piece linear intersections and other complex structures (Fig 2).
Overcoming Challenges in WAAM: Oxygen Contamination
One of the significant challenges in WAAM, mainly when working with reactive materials like stainless steels, nickel alloys, and titanium, is protecting the weld and surrounding metal from oxidation. In conventional welding, the inert gas from the torch can somewhat protect the hot zone. However, in WAAM applications, where complex weld geometries and three-dimensional structures are standard, inert gas coverage can be disrupted, leading to oxidation and compromised weld quality.
Solutions for Oxygen Contamination:
Operations can be conducted inside a steel chamber filled with inert gas to address this issue. However, this approach, while effective, is expensive. A more cost-effective solution developed by Huntingdon Fusion Techniques (HFT®) involves using Flexible Enclosures®. These enclosures, made from advanced engineering polymers, provide a controlled environment for WAAM operations, offering significant advantages over traditional vacuum or glove box systems. HFT®’s flexible enclosures are available in a range of sizes, up to 27 cubic meters, and can accommodate all workpieces, welding equipment, and even programmable robotic systems.
Monitoring and Controlling Oxygen Levels
Ensuring that the oxygen content within the enclosure remains low is critical for maintaining the quality of the welds produced by WAAM. HFT® has developed advanced Weld Purge Monitors® capable of measuring residual oxygen levels down to 10 ppm. These monitors provide continuous data acquisition and logging, with features that allow operators to control deposition between set oxygen levels. Relay contacts can trigger alarms or even control welding power supplies if oxygen levels exceed acceptable limits.
Advantages of Flexible Enclosures® for WAAM
Flexible enclosures offer several advantages over traditional metal or vacuum systems:
Wire and Arc Additive Manufacturing (WAAM) has proven to be a game-changer in producing significant, complex components for the marine and aerospace industries. By leveraging advanced welding techniques and innovative solutions like Flexible Enclosures®, WAAM allows for the efficient and cost-effective production of custom parts while maintaining high quality and durability standards. As WAAM technology continues to evolve, it is set to play an increasingly important role in the future of manufacturing.
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