Interview: Professor Neil Hopkinson and the invention of Xaar High Speed Sintering 3D printing

High Speed Sintering
(HSS) is a method of end-use 3D
printing production 20 years in the making. Professor Neil
Hopkinson invented and patented the technology at Loughborough University and,
working with Xaar, chose to make the move toward
commercialization in 2005.

Recently, at the company’s 3D Technology Day in Nottingham,
Neil who is now the Director of 3D Printing at Xaar led a
personal tour of the company’s additive manufacturing
development and demonstration facility.

Here I was treated to a preview of Xaar’s forthcoming HSS 3D
printer, project named ‘Little Blue’, heading to select
partners at the end of 2018.

Xaar's HSS system, nicknamed "Little Blue" in action. Original video and clip by Beau JacksonXaar’s HSS system, nicknamed “Little
Blue” in action. Original video and clip by Beau Jackson

A combination of SLA and injection molding

HSS 3D printing was an idea hatched by Neil studying for his
PhD. The project, funded by 3D Systems, looked at the viability
of SLA 3D printed molds for use in injection molding. As a
matter of course, Neil gradually identified the scope for
combining the two processes, cutting out the mold-making middle
man, and ramping up rapid prototyping an end-use process.

The technology at the core of HSS development is laser
sintering. The analogy Neil gives to that process of using a
laser to sinter powder “is almost like using a biro to color in
a wall. It’s not an effective route to do that.” He adds,

“How can we find a more effective, time and cost efficient
means of converting this powder in laser sintering into a
part. And that’s the answer – to take the laser out.”

The carbon black test

Print heads in the HSS process lay an infrared absorbable ink
onto the powder bed. When the bed is irradiated, the ink
absorbs the energy from the infrared lamp and melts the
underlying particles.

Explaining the synthesis of this process, Neil says, “I got
some laser sintering powder, two little lumps of it, one was
mixed with carbon black, and one wasn’t. I heated them up with
a lamp. That one (with carbon black) did, and that one
(without) didn’t, and I thought – this is going to work.”

To realize his ideas, Neil needed an inkjet printhead that
could withstand the high temperatures needed to fuse polymeric
powders. After discussions with a number of printhead
producers, it was Xaar that came throught with the support
necessary to trial their printheads and, after initially
overcompensating on cooling, and literally “frying” the head,
it worked.

Inside Little Blue

Working to commercialize the technology, Xaar has opened up the
licensing of the HSS process. This allowed other companies,

such as voxeljet,
to develop their own variants.

Xaar’s own “Little Blue” HSS 3D printer is at the alpha stage
of development. The current build volume is about the size of a
typical house brick. As a demo 10 palm-sized (each
approximately 4 in long, 1.5 inches wide and 0.5 inches deep)
articulated fish bones were 3D printed.

For a job of this scale and complexity, it takes Little Blue
about 2 hours to complete the print.

HSS will have bigger fish to fry in the future. Photo by Beau JacksonHSS will have bigger
fish to fry in the future. Photo by Beau Jackson

Plenty more fish still to come

In order to retain this performance, the build chamber is
subject to precise thermal stability across the entire build
plate, which is the main challenge to scaling up the HSS

With development, HSS is intended to be faster than the
competition. Speed, and the scale of the system is one of the
key R&D goals of Xaar’s
sister team in Copenhagen.

“With our Copenhagen team, it’s pretty obvious that we’ve taken
them on to build equipment,” explains Neil. “We can’t give
specific details of that equipment, in terms of the bed sizes
and so-on, but as an industrial system it will be a bigger bed
size than this, and it will run quicker.” In a figure of speech

“So that will enable us to build a far greater number of
fishes, in a smaller amount of time.”

Has Xaar struck gold with HSS technology? Photo of 3D printed Snitch sample from the world of Harry Potter by Beau Jackson.Has Xaar struck gold
with HSS technology? Photo of 3D printed Snitch sample from the
world of Harry Potter by Beau Jackson.

More inkjet 3D printers the world over

As a technology with strong 2D foundations, many people in the
industry believe that inkjet technology will be the future of
3D printing. Keen to make the most of this opportunity, in a
second business segment Xaar is also directing its efforts to
supply inkjet 3D printheads to international OEMS.

In addition, Xaar has been working with materials
manufacturers, including BASF, and other interested parties to
test the capabilities of their components.

Xaar’s 2018 3D Printing Industry Awards nominated High Laydown
Technology (HLT) is one process at the “heart” of rapid and
scaleable additive manufacturing processes. A jetting process
that allows for the high throughput of viscous liquids, HLT
will also be applied in Xaar HSS systems to get high strength
parts and expand its materials portfolio.

Sample materials developed in a Xaar/BASF collaboration. Photo by Beau JacksonSample materials
developed in a Xaar/BASF collaboration. Pen for scale. Photo by
Beau Jackson

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Featured image shows Neil Hopkinson, Director of 3D
Printing at Xaar, holds a couple manifold part 3D printed using
HSS. Photo by Beau Jackson

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