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.”

Hybrid approach
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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– Arkema emphasises 3D printing in its materials research agenda
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As promised in the flyer, the Association of Laser Users (AILU) event brought together a mix of additive manufacturing (AM) experts from industry and academia to discuss the tough topics that are all too often ignored in the media hype surrounding 3D printing. Split into four sessions, the meeting was chaired by Robert Scudamore from manufacturing and fabrication consultants TWI.

Setting the scene
The aerospace sector is a prime candidate for lightweight, lattice structures that are easy to build using AM tools. Also, 3D printers enable a high-level of part customization, which benefits medical implants and patient-specific surgical tools. But both aerospace and medical sectors require significant materials and process qualification.

Also, there are setup costs to factor in. Additive techniques such as 3D printing use much less material than subtractive processes such as milling, but the initial materials outlay can still be high. For example, filling an industrial laser sintering machine with virgin titanium powder can cost thousands of pounds.

Speed of production is another issue, with some parts taking hundreds of hours to build.

Reality check
One of the first speakers to start busting the myths was Robin Wilson from the UK’s Technology Strategy Board (TSB). “Additive manufacturing is not just printing from CAD,” he told delegates. Potential users need to consider the whole process, which as Wilson points out involves a significant “digital data supply chain” and physical “post-processing” of the finished component.

Stéphane Abed of Poly-Shape, who also spoke at the meeting, manufactures parts using a tool path that co-ordinates four beams. These multiple lasers can build several smaller components at once or construct different sections of a single work-piece simultaneously, to improve production rates. But having multiple optical-trains also ramps up the number of variables in the process.

Listening to the presentations, it’s clear that AM has no shortage of parameters that influence the quality of the manufactured part – laser power, writing speed, powder flow rate (for nozzle-blown setups), particle size distribution and recycle rate, are just a few.

It can be done
Throughout the day, process control remained a key talking point. Trevor Illston of Materials Solutions, who led the final session of talks, is optimistic that AM can be controlled to a “production standard” by inspecting workpieces at multiple points in the AM process.

Giving the audience food for thought, Illston added that there can be a downside to the design freedom that 3D printing brings to the table, as it’s possible to create parts that are incredibly difficult to examine!

In general though, unlocking traditional design constraints is a big win for AM – and despite the production challenges, all of the speakers recognized that major opportunities are up for grabs.

The medical sector is a growth area for AM, not just for implants, but also for custom tools such as cutting blocks to guide surgery. Medical centres are looking at options for manufacturing parts in hospital to speed up delivery to the patient. Ideas here include flat-packed production tools that can be sterilized and then assembled in theatre.

“AM often solves one problem beautifully, but it can create other issues,” said Edward Draper of JRI Orthopaedics, who spoke in the opening session. Draper picked up on Wilson’s earlier remark about post-build processing, and emphasised the requirement for cleaning and polishing.

Something new
Images of medical devices, helicopter components and fixtures for satellites are becoming a familiar sight at AM conferences and events, but Neil Burns of Croft Engineering had something new for the audience – filtration parts. Traditionally, Croft Engineering has made filtration supports by shaping wire mesh, but the bending process leads to apertures that are non-uniform. To get around this, Burns showed how his company uses AM (inspired by a trip to Fab Lab in Manchester, UK) to build filtration supports with holes that are aligned to the direction of fluid flow – a design feature that saves customers money by reducing the amount of energy that’s required to pump liquid through the component. Despite the benefits, Burns revealed that clients can be cautious about using AM parts. They fear downtime caused by mechanical failure.

But what is the effect of AM on materials performance? How do AM samples behave under load compared with material that has been cast or milled? AM components might look fine on the outside, but what’s happening to the internal structure of the material? Also, how does the strength of parts made using different machines compare, or parts that are built on the same machine, but formed using a different tool path, or using powders with a different particle size distribution or storage history?

Team effort
To tackle this, AM needs its own materials database and standards – a point made by many attendees, including Neil Mantle of Rolls-Royce. What’s more, the task requires a collaborative effort. Contributions so far include EU initiatives such as SASAM (Support Action for Standardisation in Additive Manufacturing) and the UK’s ANVIL project to establish benchmarks and design guides for AM.

A continuing development is the use of technology hubs to support AM projects at technology readiness levels (TRL) 4-6, or in other words to translate projects from proof-of-concept to pilot-scale operation.

David Wimpenny from the UK’s Manufacturing Technology Centre (MTC), which was established in 2010 to bridge the gap between academia and industry, was at the event. “Our role is to make parts that industry can relate to in terms of size and quality,” he explained.

Today, the MTC is part of the UK’s high value manufacturing (HVM) catapult – a network of seven technology centres with a shared goal of accelerating process innovation.

Related links –

Metal Additive Manufacturing: opportunities in applications and improvements in process technology (full programme)

3D printers and their extended family of additive manufacturing (AM) tools have been dismissed by some as being too slow for mass-production, but there are game-changing opportunities on the horizon – as highlighted at yesterday’s industry summit in London. Big names such as Airbus, Boeing, EADS, Bayer, IBM and Volvo are looking at the technology in a positive light.

Bernhard Müller from the Fraunhofer Institute for Machine Tools and Forming Technology began the day by summarizing the state of play, pointing out AM’s origins as a design tool, but adding that production teams are becoming more involved with the technology.

Dyson is one of many, many firms making great use of AM for rapid prototyping and has three EOS selective laser sintering machines, two Ipro 8000 stereolithography systems and two Eden Objet 3D printers running almost full-time to road-test new product ideas.

But Jessica Middlemiss, senior materials engineer at the firm, flagged up the mismatch between the material properties of the AM components compared with downstream injection moulded versions – an issue that makes it much harder to predict final product performance.

Help could be on its way though.

Thomas Buesgen, senior project manager 3D printing at Bayer Material Science, revealed that they are working hard to provide materials for AM that are more elastic, highlighting a new product – TPU 92A-1 – a thermoplastic designed for SLS systems that is being marketed as the first fully-functional flexible material in 3D printing.

Buesgen also observes that the injection moulding sector is keeping a much closer eye on AM, another sign that layer-by-layer assembly is being taken more seriously in manufacturing circles.
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Low-cost 3D printers have done a great job of putting additive manufacturing (AM) – the process of making objects layer upon layer – on the map, but they only scratch the surface of what this approach has to offer. To see the full range of opportunities, it’s worth taking a deeper look.

The European collaboration of rapid manufacturing has done just that and its 2013 Strategic Research Agenda (SRA) report (PDF) is a worthwhile read for anyone wanting to know more about a field that also goes by the name of direct digital manufacture or e-manufacturing.

Frits Feenstra, who co-ordinates the platform, is well versed in AM, which encompasses a range of processes such as powder bed fusion, directed energy deposition and material jetting.

“3D printing brings something different to the party,” he told delegates at COMS 2013. To support the comment, Feenstra points out that AM gives you the opportunity to embed sensors or to integrate multiple materials and create graded structures with a distribution of physical properties.

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