It was conceived and designed from first principles, from the ground up. As a result, it has decisively improved the weld properties, optimised the communication between man and machine, and perfected the handling. The pursuit of quality has increased the demands on the welder exponentially. He is the human link between two materials, and the modern welding system is the amplifier of his senses. This not only requires an adaptation of the welding processes, but also a revision of the interface between man and machine.
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Additive production methods generate components by building up material layer-by-layer, the most well-known example being 3D printing. WAAM, which is based on the arc welding process, also produces metal parts layer by layer, with the layers formed by melting and fusing a wire electrode. This generative method is particularly advantageous when complex component geometries have to be produced, as the design options are virtually limitless. In comparison, processing time, tool wear and material loss during traditional machining — especially with the conventional approach of milling out the workpiece from a solid block — all result in significant additional costs.
There are a number of generative production methods for metals. Essentially these can be divided into two fundamental types: powder-based processes and wire-based processes.
In powder-based processes, the layers are built up using molten metal powder. The most common method, the powder bed process, produces extremely precise results, but is somewhat slow in production. Wire-based processes, on the other hand, build up the component by melting a wire-based filler metal, using a laser, electron beam, or a welding arc.
These processes have a high deposition rate and therefore help to cut production times. Wire arc additive manufacturing is a wire-based process that uses the gas metal arc welding process GMAW. WAAM itself offers a number of advantages. First is its high deposition rate up to 4. Equipment and material costs are also important criteria, which is another strength of WAAM: all you need is a suitable welding system. There is no requirement for costly special equipment, such as the vacuum chambers needed for the faster electron beam process.
In comparison to powder-based processes, WAAM benefits from the immediate availability of a range of certified wire types. Since the use of metal powder is a relatively new technology, there are comparatively few powder-based materials to choose from, as it can take years to acquire the necessary certification and to produce data sheets. A stable welding process and effective heat dissipation are essential for WAAM. The welding process needs to be sufficiently low energy such that when a new layer is applied, the existing layers are not remelted.
Furthermore, the weld layers need to be continuous, spatter-free, and consistent. If any flaws were to occur, these would be transferred to each subsequent layer. It produces a stable arc and a controlled short circuit with long short circuit times. This means that the heat input is very low and the material transfer is practically spatter-free, which helps to prevent flaws. It achieves high deposition rates while transferring very little heat into the component.
The CMT Cycle Step variant reduces the arc power even further through the controlled deactivation of the arc during the process phase. These include fan impellers for the electronics industry, which are made from high-grade materials. Milling the workpiece is very expensive owing to the high rate of material consumption, while casting is not always able to meet the critical metallurgical properties required for wall thicknesses of just 1.
Fronius has also implemented an application with a partner in the aviation sector. Titanium is a frequently used material in aircraft construction thanks to its tensile strength, resilience, corrosion resistance, and low weight.
This results in high costs, long machining times and costly tool wear. On the other hand, components produced using WAAM need only a final machined skim to produce a smooth surface.
The titanium components produced using the CMT additive process do not exhibit any lack-of-fusion problems and they have impressive metallurgical properties. Tool costs, machining times and wear are significantly reduced, meaning that overall manufacturing costs can be brought down.
This makes WAAM a cost-effective and flexible alternative for component production. The additive process can be adopted with relative ease using welding technology from Fronius and its CMT solution.
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