Additive manufacturing (AM) is a major opportunity for materials translation. Layer-by-layer fabrication gives designers the freedom to specify lightweight and highly-integrated components that would be impossible to manufacture using conventional machining or forging techniques. To find out what AM can deliver today and to discuss what’s in the pipeline, TMR+ spoke to presenters at Trends in Advanced Machining, Manufacturing and Materials (TRAM) 2015 – an event supported by Boeing and organized by the UK’s Advanced Manufacturing Research Centre.
For the aerospace industry additive manufacturing is synonymous with powder metallurgy. At the meeting, Robert Smith Graham of Carpenter Technology described the gas atomization technique used by his company to produce powders of alloys based on nickel, iron, cobalt and – in a new venture for the firm – titanium.
Smith Graham stressed the need to define standard metrics for the metallic powders used for aircraft parts, as well as agreed measurement techniques. “The additive manufacturing community has already identified this key issue, and work is already underway with academic institutions, research agencies and other manufacturers to define standard specifications,” he said. “Particle size distribution is one important parameter, and we need to find a consistent way to measure this and other key properties.”
Greg Hyatt of DMG Mori Seiki, a manufacturer of machine tools, highlighted that innovation in laser technology has been crucial for making the technique a viable proposition for aerospace applications. “Commercial laser systems are now capable of producing powers of up to 10 kW,” he said. “This means that we can now deposit kilograms of material per hour rather than grams, which makes the whole process much more cost efficient.”
Even so, Hyatt believes that more innovation is need to make additive manufacturing cost-competitive with other metal-processing techniques. He points out that build costs could be reduced significantly by depositing layers onto standard forged parts. “This approach retains the robust mechanical properties of the forged piece, and then additive manufacturing can be used to create fine structures on the part surface. This offers real added value at a much lower cost.”
At the same time, additive manufacturing is becoming more precise, making it possible to tailor the mechanical properties for different areas of the component. “We have case studies where we have deposited materials onto existing parts at rates of more than 10 kg per hour,” said Hyatt. “We have also demonstrated how precise additive manufacturing can yield layers with graded composition.”
Hyatt wasn’t able to share the detail of the case studies, but said that good results have been achieved for a rocket motor nozzle. These components must accelerate a large volume of combustion gases to supersonic velocities within a very short distance, and so must be made from materials that can withstand extreme forces and thermal loading. At the same time, their complex structure requires a number of different machining processes to produce using conventional manufacturing techniques.
According to Hyatt, this highly functional type of part is the current sweet spot for additive manufacturing in the aerospace industry. But, as other talks at the conference revealed, many other applications are waiting in the wings for this truly disruptive technology.
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