“Metal 3D printing (3DP) or machining metal parts can be a costly process. Some say 3DP for metal parts offers more advantages than other techniques, including CNC machining. But that is where a lot of confusion sits. Metal 3D printing like any other manufacturing technique or process, has its own specific advantages and drawbacks that need to be weighed up in relation to the task at hand. The point of it is that it offers manufacturers options – another way of doing things,” explained Christo Botes, Director and one of the original founders of Metallurgical and Manufacturing Services.
“Reduced waste, production efficiency and functional gain driven by greater design freedom and flexibility is really what everybody is looking for,” continued Botes.
“This is why we investigated Wire Arc Additive Manufacturing (WAAM). Metallurgical and Manufacturing Services is an expert welding company that specialises in the refurbishment of metallic components manufactured from special alloys.”
“WAAM is one of the lesser-known metal 3D printing technologies, but one that holds huge potential for large-scale 3D printing applications across multiple industries.”
An example of a basic component that was printed using the cold metal transfer principle. The component is then finish machined. One of the advantages of the Wire Arc Additive Manufacturing (WAAM) and cold metal transfer is that you get the exact size you need and don’t have to rely on off-the-shelf supply that requires additional machining or cutting. Another advantage is that you are not paying for expensive transport of expensive material and the extra material (drop-out) that will be scrap metal, if the component is a ring (example in picture – material used Nickel-moly 13-4)
“WAAM is a variation of a Direct Energy Deposition technology and uses an arc welding process to 3D print metal parts. Unlike the more common metal powder AM processes, WAAM works by melting metal wire using an electric arc as the heat source. The process is controlled by a robotic arm and the shape is built upon a substrate material (a base plate) that the part can be cut from once finished,” explained Botes.
“The wire, when melted, is extruded in the form of beads on the substrate. As the beads stick together, they create a layer of metal material. The process is then repeated, layer by layer until the metal part is completed.”
“WAAM can work with a wide range of metals, provided they are in wire form. This list includes stainless steel, nickel-based alloys, titanium alloys and aluminium alloys. Any metal that can be welded can also be used with WAAM.”
The benefits of WAAM: The ability to 3D print large metal parts
“WAAM is particularly suited to manufacturing large-scale metal parts. This is in contrast to Powder Bed Fusion (PBF) metal AM technologies, which typically produce smaller, high-definition components.”
“Unlike PBF AM machines, which have a limited build envelope, the robotic arm of a WAAM machine has more freedom of movement, meaning that the size of a component isn’t limited by space, but only by the distance the robotic arm can reach. This allows for the production of larger parts, which wouldn’t be possible with PBF processes.”
Cheaper process and materials
“In terms of material costs, the welding wire used in the WAAM printing process is significantly less expensive than the metal powder used in metal PBF.”
“This is because WAAM technology is based on welding, a well-established manufacturing technology itself. WAAM hardware usually includes off-the-shelf welding equipment, which is less expensive than many metal 3D printers available on the market.”
“Additionally, wire is typically easier to handle than powder, which requires specialised protective equipment to use.”
“Parts produced with WAAM are particularly notable for their high density and strong mechanical properties, which are comparable to parts manufactured with traditional manufacturing methods.”
“As the wire feedstock is a 100 per cent dense input material, there is negligible porosity induced in the fabrication process, leading to a very dense final part.”
It’s suitable for repair operations
“WAAM is also a good option for repair and maintenance operations for specific components like turbine blades, as well as moulds and dies.”
“Worn-out features or damaged parts can be repaired with WAAM by depositing new material on its surface. This can result in significant cost savings as it eliminates the need to produce a new part from scratch.”
The limitations of WAAM: Residual stresses and distortions
“One challenge associated with WAAM is heat management. The printing process involves high temperatures, causing the build-up of residual stress, a problem commonly faced with metal 3D printing. As residual stress can often lead to deformations in a component, cooling must be factored into the process.”
Some materials require shielding
“When using certain materials, like titanium, shielding is necessary to create an inert atmosphere to ensure the right building conditions. This means that the process has to take place in an inert gas chamber. However, the inert gas chamber limits the size of parts that can be produced with this technology and installing such a chamber will increase the cost of the equipment.”
“WAAM typically produces near-net-shape parts with a poor surface finish. The surface of a part therefore needs to be finished via machining but the savings in terms of costs that are achieved are phenomenal if you have to machine from block or you have to have components cast or forged and then machined.”
Advantages and disadvantages
“The overwhelming advantage is that in future you will be able to order components to the exact size that you need and don’t have to rely on off-the-shelf supply that requires additional machining or cutting. Another advantage is that you are not paying for expensive transport of expensive material and the extra material (drop-out) that will be scrap metal once machined or cut, if the component is a ring (example in picture – material used 13-4 nickel moly).”
Together with Jendamark, who are the agents for Kuka Robots in South Africa, Bolt & Engineering Distributors have now installed a Fronius / Kuka Robots WAAM system in their Metallurgical and Manufacturing Services’ Centurion, Gauteng facility and they have begun to produce components
“The disadvantages are that the special alloys that you want to use are not easily available in South Africa and you generally have to find a supplier internationally. Then there is the cost of importing the wire and the lead times associated with importing.”
Teaming up with Bolt & Engineering, Jendamark, Fronius and Kuka
“The emerging research on WAAM techniques and the feasibility of economically producing large-scale metal components led us to Bolt & Engineering Distributors. As we are mainly a specialist welding company, we have now standardised on Fronius welding products and Bolt & Engineering Distributors are the official distributor of Fronius products in South Africa.”
“We said to them we want something that is going to work. No messing around we want it to work from the beginning,” explained Botes.
“They accepted the challenge. Because significant progress has been made in the understanding of the WAAM process, as well as the microstructure and mechanical properties of the fabricated components, they introduced us to the process. As WAAM has evolved, a wide range of materials have become associated with the process and its applications.”
“Together with Jendamark, who are the agents for Kuka Robots in South Africa, Bolt & Engineering Distributors have now installed a Fronius / Kuka Robots WAAM system in our Centurion, Gauteng facility and we have begun to produce components.”
Cold metal transfer
“The technology that the system is using is cold metal transfer. Cold metal transfer technology has revolutionised the welding of dissimilar metals and thicker materials by producing improved weld bead aesthetics with controlled metal deposition and low heat-input. Cold metal transfer welding is a modified MIG welding process based on a short-circuiting transfer process developed by Fronius.”
“The integration of materials and the manufacturing process to produce defect-free and structurally-sound deposited parts remains a crucial effort into the future. We believe we have found the solution in WAAM,” concluded Botes.
For further details contact Metallurgical and Manufacturing Services on TEL: 012 661 0922, Bolt & Engineering Distributors on 011 824 7500, Jendamark on 041 391 4700 or visit the websites on www.mmservices.co.za, www.bolteng.co.za, www.jendamark.co.za