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AM and sustainability
How AM contributes to energy saving in conventional metalworking processes Looking at AM’s broader contribution to energy saving, in the casting industry, AM is used to make complex ceramic investment casting moulds and cores. They do not require casting patterns and tooling, nor do they need to be dipped multiple times in a ceramic slurry and burned out, but AM offers the potential to raise the energy efficiency of even the most long-established technologies. The double-inlet nozzle casting with internal channels, shown here, was produced with an additively manufactured ceramic mould and cores (Courtesy Aristo-Cast)
(Fig. 4). In PBF systems, material is heated to its melting point by a laser or electron beam. For hightemperature superalloys, such as Inconel 718, this is at about 1,300°C. Additional energy may be required to heat the build chamber and maintain an elevated temperature during the build. Metal Binder Jetting systems use temporary binders to bond particles prior to sintering. These binders are eventually burned out or chemically removed, so they are another consumable. When sintering, parts are brought to elevated temperatures just below the material’s melting point and held for extended periods of time. For parts with thicker crosssections, this time can be extended to ensure sufficient densification. All of this contributes to the cost of energy.
Vol. 6 No. 1 © 2020 Inovar Communications Ltd
Despite this, sintering-based processes have been shown to be significantly less energy consuming than forging, casting, and machining, even when taking the energy used in metal powder atomisation into account. Fig. 5 shows data from research undertaken at GKN Sinter Metals, which is primarily focused on PM and MIM processing. It is possible to use the data generated to understand the energy consumption of mid-to-high volume sinter-based AM processing. Energy costs are present in any forming process in which metal is melted. AM’s energy advantage is the heating of minimal material to form a part, harkening back the argument for DfAM to minimise part mass.
Conclusion Metal AM processes are complex, and require experience, testing, qualification and parameterisation in order to use them as a reliable method of production. With conscience, common sense, and some ingenuity, the technology progresses toward becoming a sustainable solution.
Authors Olaf Diegel, Ray Huff and Terry Wohlers Wohlers Associates, Inc. Fort Collins Colorado 80525 USA www.wohlersassociates.com
Metal Additive Manufacturing | Spring 2020
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