Powders for Additive Manufacturing: There’s a MAPP for That! Part 2

By on April 12th, 2018 in Event

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 At the Manufacturing using Advanced Powder Processes conference
At the Manufacturing using Advanced Powder Processes conference

Manufacturing using Advanced Powder Processes is increasing in both quantity and quality, and these are indeed the fundamental drivers for the foundation of the EPSRC Future Manufacturing Hub: MAPP. Launched in January of 2017, one year on MAPP hosted its 1st International Conference over two days in Sheffield. 

This is part 2 of a two part series. Part 1 is here

Describing the current situation of defect identification in AM as a “minefield” he went on to evoke the “dream,” namely “put metal powder into a machine – press go – get a high integrity part out!” I think every AM user has probably daydreamed about that scenario at one time or another. However, we’re not there yet and Professor Clare is one of many people figuring out how to get closer to that. After highlighting many of the challenges (powder variation, energy sources, design choices, parameter choices, inspection limitations etc) he went on to outline a “hierarcy of needs for analysis.” Specifically:  

• Part validation
• Process improvement – available for CNC, not AM
• Process monitoring
• Online validation – on the fly
• Online correction – intelligent machines (the panacea) correcting on the fly. 

And while Adam identified some commercial analysis tools that are starting to emerge from vendors, he delved into the research he is conducting at Nottingham, which takes a different approach – spatially resolved acoustic spectroscopy — the goal of which is to develop an “information rich production machine” supported by in-process monitoring (online), which requires a specific instrument in the machine. There are many logistical challenges here, including the optical measurement of rough surfaces; fitting the tool inside the build chamber and the necessity to miniaturise the optical train and use of galvanometer; as well as the impact on build time. Moreover, beyond monitoring the research is considering how to produce real time feedback and correction / action by developing algorithms for controlling microstructure repair. 

This information was delivered so well, it actually lifted the room, the potential excited people — even more so considering what it enables: the ability to effect rework in-process, which will drastically enhance the economics of AM. 

In a similar vein, Andrew Moore of Heriot-Watt University and Peter Lee of the University of Manchester also provided research insights into the “High speed imaging of the powder bed and shield gas during metal PBF additive manufacture” and “Shining new light on the mechanisms controlling laser additive manufacturing using synchrotron imaging” respectively. 

Again, there were some fascinating videos, courtesy of high speed imaging (8000 frames per second) and Schlieren imaging techniques that provided real time footage from within the chamber showing laser meltpool spatter etc, at different angles and speeds. It was incredible imagery that offers real learning material. Some of the ideos are available online. 

Other presentations across the event drilled down into projects funded through MAPP. Notable among these the work being undertaken at the Harwell campus and research complex (home of the diamond light source) to develop and build new equipment using synchrotron hard X-rays to see inside the build – not just the surface of it, to track what happens layer by layer and then build up a valuable data set including a process map and a mechanistic map. Beyond the process, however, and in line with the MAPP remit, the research here also investigates powder quality and new material development including comparing virgin powder against oxidised powder to understanding how much oxidisation can be tolerated without impacting quality. It was interesting to learn that “powder flows better when slightly oxidised” but the team is looking to discover how AM can be used with a laser to directly process ceramics and correlate results with other methods (Optical and IR / X-ray etc) as well as develop machine learning algorithms based on what is happening in the meltpool. 

Another key theme of MAPP research with a dedicated session at the conference is that of Advanced Characterisation. This is a fascinating area of research, and at this conference it was all about the what, why, where, who and how material characterization was progressing for AM – once again many of these details were beyond my brain power. Essentially, though, these details are not pre-requisite for the vast majority of the AM industry, but I know that the results are, and they will have a massive impact on future industrial capabilities of the technology in the real world. That’s a key take-away here. Indeed the MAPP conference provided repeated examples of why such conduits between academic research and industry are vital. 

As you might expect, the characterisation of material powders is a complex and multi-disciplined field that involves understanding — and utilizing — their physical structure and chemical composition to understand and measure their properties, including but not limited to stiffness, strength, ductility, hardness, electrical/thermal conductivity etc, in relation to how they can be processed, react in-process and ultimately, finished part quality and integrity. 

Prof. Jin Ooi from the University of Edinburgh looked at this from a top down view with his presentation: Computational modelling of powder processes from model conceptualisation to industrial application; while Hongtao Zhang from Loughborough University got more specific with the “Microstructural characterisation of oxide dispersion strengthened ferritic steels fabricated by spark plasma sintering for nuclear applications.” 

The two days were concluded with a final session comprising an expert panel talking about getting “from research to results: Is powder research responding to industry needs?” And chaired, expertly by Sophie Jones, General Manager of Added Scientific.

Rounding Up 

I think my biggest take-away that I can share is that this event provided an opportunity to better understand the advanced techniques that are taking place deep inside the PBF additive manufacturing platforms. Powders demand a different approach to other material states and this is the remit of MAPP — to find the best ways to make powders work for industrial applications. 

A Few Other Insights

The conference, as often is the case, included an evening dinner reception — these things serve multiple purposes. The obvious one of necessary refuelling after brain overload is superseded by the opportunity to network with other attendees. On this occasion, my dinner companions for the evening were most lovely – Iain Todd, Hugh Hamilton (Johnson Matthey), Kelly Moran (AMRC / Rolls-Royce) Dan Johns (Oerlikon), and Javier Llorca (IMDEA Madrid).

Conversations were free flowing and varied and often reverted back to families and commonality — a vital under-pinning of human interaction. Of course, there was a great deal of chatting about the MAPP commonality (the reason we were all sat at the same table) its intent, where it fits in the UK AM community/global ecosystem, academic community and more. The breadth of experience, global locations and motivations and how we interacted were a perfect analogy for the current status of AM, I mused. 

The conversation that nearly tipped me into a heavy depression, however, was with Dan Johns, now at Oerlikon (a company that is a great example of investment and scaling up with AM), when we were discussing the early days of RP and our longevity in this industry of ours — always fun. The cloud descended though when Dan pointed out that there were probably people in the room that hadn’t been born or were still in nappies when we started out in this industry. Seriously, my hysterical l
aughter was a very thin mask! 

But to sum up, it was a really interesting and useful event to attend — not too big, lots of extremely intelligent people, with passion in abundance soaking up the science behind some fundamental AM developments — disseminating, reporting, sharing and learning. How it should be.

This is part 2 of a two part series. Part 1 is here

By Rachel Park

Rachel Park is an accomplished print and web writer and editor with more than 24 years’ experience. Her specific area of expertise is the 3D Printing and Additive Manufacturing sector, a market she has been immersed in since 1996.  Rachel works as an independent freelance journalist and runs her own copywriting and editing business.