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.
The venue
was the old yet beautiful Royal Victoria hotel — a building steeped in British
history that permeated the corridors, halls and rooms at every turn. Originally
named the Victoria Station Hotel when it opened in 1862, to describe its
proximity to the primary railway station in Sheffield and to recognise the
British Monarch on the throne at the time, it was later renamed the Royal
Victoria to coincide with a visit from the Prince and Princess of Wales in
1875. More than twenty years later, Queen Victoria herself was a visitor there
just as the first industrial revolution was taking place.
As
Professor Iain Todd, an Additive Manufacturing (AM) industry veteran and
project leader at MAPP pointed out in his welcome address: “Sheffield is one of
the homes of the 1st Industrial Revolution, so it is really
interesting that around the city we are witnessing a renaissance with the AMRC
and advanced manufacturing park.” Moreover, he also highlighted how the
university and the city are contributing to the 4th Industrial
Revolution / Industry 4.0. “Our future manufacturing hub is part of that – and
this conference is one of the activities in this regard.” MAPP’s central
premise is to deliver on the promise of powder-based manufacturing to provide
low-energy, low-cost and low-waste high value manufacturing routes and products
to secure UK manufacturing productivity and growth. Relatively speaking, it is
actually a narrow and specific remit, but one that is absolutely fundamental to
progress with high end with a broad
reach into a number of connected industries.
The goal of
the first MAPP conference was to draw together scientists, researchers and
commercial powder manufacturers from around the world and at every career stage
to disseminate the work — and progress — that is being made in this area.
Across the
AM industry emphasis is often placed on process capabilities, however
fundamental to many processes are the powdered materials that are fed into the
machines. Off-the-shelf, these materials can prove to be variable in terms of
performance and quality, and this is where MAPP is looking to make a
difference. Talking to Professor Iain Todd, one on one, among a variety of
topics, he provided a really quite useful analogy for me, one that provided him
with a light bulb moment when it happened! He had been talking with a manufacturer
of crisps (or potato chips for any US readers). They’d been discussing
materials, and this person had described the base material for crisp production
as the potatoes. Obviously, you might think, but then consider; if the input is
“potatoes” the output always has to be the same 35g ±0.5g! How many potatoes
are the same size and shape? Ok, so it’s not a direct analogy, crisp packets to
not contain uniform contents, but it serves to illustrate how MAPP is looking
to promote powdered materials that are designed for process, monitored in
process to ensure an output with designed quality — and to provide the science
to back it up. It’s not all new science either, a great deal of it intersects
with the food and pharmaceutical industries, Iain said.
Conference
Programme
A carefully
curated mix of in-depth keynote presesentations (based on research) together
with some faster paced talks and followed by round table Q&A’s were blended
well to provide delegates with an engaging format. There was also a session
dedicated to some head-spinning “flash presentations” as well as a poster competition
detailing the many areas of research being conducted (29 in total) — in a bid
to provide insight into the comprehensive scope of the MAPP initiative. The
interactive poster session, invited delegates to vote for their top three
posters during the course of the event. Indeed,
networking
opportunities were abundant, and formally recognised as a key motivating factor
for conference attendance. It was also heartening to witness the real diversity
across the programme.
Content
The key
powder material themes driving Mapp research were consistently in view, focused
as they are on novel in-situ observation, characterization and modelling
and control, to gain deeper understanding of the interaction between complex
processes and materials.
It’s
probably important to note, at this point, that what followed involves a great
deal of high level science, much of which went straight over my head and left
me scratching said head at times! The point, though, is that this scientific
activity is intrinsic to AM progress and it is happening.
The first
in-depth session focused on “In-situ process and performance characterisation”
and was keynoted by Professor Tresa Pollock from the University of California.
It was hard not to make a mental note that starting with a strong female
presenter was a nice touch, however, if it was unintentional — even better. Prof
Pollack’s presentation considered the
3D Analysis
of structure and defects at the scale of the melt pool, and provided
considerable insight into her team’s research using Femtosecond Lasers and
Tomography to achieve workable systems for 3D data set collection and analysis
during AM builds. As she noted:
“In-process
monitoring is essential.” In this way challenges can be identified and
overcome, including how “we have to think harder about designing alloys for AM
– to minimise residual stresses,” and “develop more amenable alloys, nano
functualisation of high strength alloy powders and design of solidification
paths.” This requires requires large 3D and 4D datasets, but Professor Pollock
was optimistic that Femtosecond laser tomography is a promising new approach.
Professor
Pollock’s keynote was followed by a second keynote presentation delivered by
Prof. Barbara Previtali from the Politecnico di Milano. Another
strong female scientist (and role model) working on temporal beam shaping in
Selective Laser Melting and molten pool sensing during continuous and pulsed
wave laser processing. Describing
the research approach and the experimental set up (due to commercial SLM platform set up not allowing
tests), which includes machine and materials (AlSI); pulse temporal profiles;
and high speed imaging (camera synchronised with illumination) for process
diagnosis; Professor Previtali was able to show videos of melt pool monitoring
in SLM at different build speeds, which were fascinating. The team’s subsequent
image analysis identified
molten pool attributes and provided a comparison of pulsed wave (PW) and
continuous wave (CW) laser processing using differeing modes and geometry and
concluding that a mixed strategy produces improved results, which in turn will
be the focus of future development for higher quality and productivity results
with SLM.
These very
specific, highly detailed presentations were followed by three short, fast-paced
presentations and a Q&A session. The highlight of the morning (probably the
whole event), from my point of view, was the presentation given by Prof Adam
Clare from the University of Nottingham, which considered the issue of ‘finding
and fixing defects in metal powder bed processes.’ Apart from the fact that the
title of the presentation didn’t require a definition search, and that the
science was no more or less impressive than any of the other
fields of research, Professor Clare’s insight and delivery
was wholly accessible to a layman like me. Plus, he has a wicked sense of
humour — that always helps.
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 laughter 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.
