The Coming Proliferation of High Speed Sintering?
Michael Molitch-Hou posted on April 11, 2017 |
In an interview with, high speed sintering inventor Neil Hopkinson discusses Xaar’s ...

In the last few years, a number of exciting new technologies have emerged in the 3D printing industry that promise the integration of additive manufacturing (AM) into the larger world of manufacturing, including Carbon’s Digital Light Synthesis and HP’s Multi Jet Fusion (MJF). Before these existed commercially, however, there was high speed sintering (HSS). 

A buckle part, automotive gear and pipe fitting made with HSS. (Image courtesy of Loughborough University.)
A buckle part, automotive gear and pipe fitting made with HSS. (Image courtesy of Loughborough University.)

Invented and developed by Neil Hopkinson and his team while he was performing research at Loughborough University and, later, the University of Sheffield, HSS uses infrared lamps and an inkjet printhead to outpace other AM technologies like selective laser sintering (SLS). Hopkinson is now at inkjet printhead manufacturer Xaar, where he leads the company’s 3D printing division.

As Xaar looks to fulfill its stated 2020 vision, Hopkinson and his team have just cut the ribbon on Xaar’s new 3D Centre in Nottingham, England. reached out to Hopkinson to learn just what this 2020 vision looks like and how HSS will play a role in it.

What is HSS?

HSS was developed as a means of bringing down the cost of SLS parts in order to make 3D printing competitive with mass manufacturing technologies like injection molding. By replacing the costly laser used in SLS and increasing the throughput of the machine, it’s possible to sinter parts at a pace and cost that could potentially compete with injection molding.

In HSS, an inkjet printhead deposits a black infrared radiation absorbing ink onto a bed of thermoplastic powder, outlining the desired shape. An infrared lamp then heats the powder, causing the particles to fuse. 

This opens up a number of advantages to SLS. The ability to sinter large areas at a time makes it faster than SLS, while the gentle heating of the process opens up a wide range of materials, like elastomers and other plastics. Additionally, HSS can use 100 percent recycled powder without causing a rough finish, also there is no need for a nitrogen-rich environment, as there would be for industrial SLS.

If HSS sounds a bit like MJF, that’s because, though initial patents for HSS were filed as far back as 2003, the two processes are quite similar. In MJF, an inkjet printhead deposits both a fusing agent and a detailing agent onto a bed of thermoplastic powder before sintering them with a set of infrared lamps. Hopkinson explained that the biggest difference between the two is that HSS does not use a detailing agent.

“There are obvious similarities/overlap in the approaches as both approaches print an absorber onto a powder bed; the main difference to our approach is that we don’t employ a detailing agent/sintering inhibitor,” Hopkinson said. “In the early days of working on HSS (mid-2000s) I considered bringing together HSS and Selective Inhibition Sintering developed at the University of Southern California but I found that we were able to get excellent feature resolution (0.5mm features) without the need for an inhibitor/detailing agent so we proceeded with just an absorber.”

The use of inkjet printheads also opens HSS up to the same flexibility promised by HP’s MJF. By incorporating multiple printheads dedicated to specialty materials into the HSS process, it may be possible to deposit such functional inks as silver conductive fluid. Bringing such a machine to market still requires development, but the process is conceptually feasible according to Hopkinson. To create one, Xaar’s unique business model may be quite advantageous.

Bringing HSS to the World

In 2014/15 the HSS approach of printing an infra-red absorbing ink onto a powder bed came closer to a commercial reality when a number of companies licensed the technology. In 2016, HSS took a further important step toward commercialization when Hopkinson joined inkjet printhead manufacturer Xaar as its director of 3D Printing. The company is now ready to make that happen through its new 3D Centre in Nottingham and a new group of engineers in Copenhagen, Denmark. 

“Our objective at the new centres in Nottingham and Copenhagen are to maximise the commercial potential of HSS,” Hopkinson said. “We will do this in 3 ways: i) We will design and develop HSS machines including specialist machines and machines that will be taken to market by machine OEMs. ii) We will assist materials suppliers in the development and processing of their materials in HSS. iii) We will help end users to establish how and when it makes most sense to adopt HSS by making parts a running cost analyses.”

Hopkinson elaborated that the company’s efforts in AM will be divided into two major categories—one that will focus specifically on HSS and one that will focus on 3D printing more generally. Because there are already a number of established 3D printer manufacturers that focus on UV curing resins or binding powders, Xaar is leveraging its experience manufacturing inkjet printheads for high volume industrial printing systems to create development kits for AM. 

Xaar’s inkjet development kit for 2D printers. (Image courtesy of Xaar.)
Xaar’s inkjet development kit for 2D printers. (Image courtesy of Xaar.)

“Part of our role at Xaar in terms of our 3D business is supplying what we call a development kit to companies or research organizations who are looking into building new 3D printing machines,” Hopkinson explained. “Often they need inkjet printheads for the 3D printing machines, so they come to us and ask about using that. We provide them with a development kit and it helps them to make machines and do some early proof-of-concept work.”

Bundled with this AM development kit will be software from leading AM software developer Materialise. As new inkjet 3D printing systems are being developed, software will be necessary for file preparation as well as for control over the printer itself. Therefore, Xaar thought it sensible to become a one-stop shop for its customers by bundling its own hardware with Materialise Magics, for preparing data, and Materialise Standard Image Build Processor, for transforming this data into an inkjet machine specific data format.

This benefits both the customers, who will be able to use the software for new printers in development, as well as Materialise, which may become an obvious partner for these machines as they are prepared for market. 

In terms of HSS, Xaar will be offering an even more comprehensive solution for customers wishing to develop HSS-specific 3D printers. In this regard, Xaar will not just offer a development kit but a complete service for aiding original equipment manufacturers (OEMs) in the design of new machines. 

The HSS printhead performing a print. (Image courtesy of Loughborough University.)
The HSS printhead performing a print. (Image courtesy of Loughborough University.)

“[T]here are plenty of companies that have the infrastructure to sell and service HSS machines,” Hopkinson said. “It makes sense to partner with those companies to bring the technology to market. What we have is many years’ experience in designing powder bed machines and in developing materials and applications. There is a range of ways we can commercialize our offer ranging from sales of services to sales of subsystems that go beyond just the print system.”

Who these customers are remains to be seen. So far, one company that has been public about licensing its technology for HSS is Voxeljet. This manufacturer of large-scale sand 3D printers has said that it will be ready to launch an HSS machine by 2017 or 2018. According to Hopkinson, Voxeljet is actually the smallest firm to have licensed the technology so far.

Xaar will also be working with materials suppliers, both in terms of inks and powders. Hopkinson pointed out that the process of developing new powders for AM isn’t as easy as grinding up a polymer used for injection molding and expecting it to work in SLS or HSS.   “Getting the materials right for a new 3D printing technology is extremely important,” Hopkinson said. “We have become very good at helping materials manufacturers screen their existing portfolio of materials and also helping them find where to make changes to their materials to make them suitable to the process. This will help them create a new revenue stream through HSS. That’s something that we’ve become very efficient at. One of our key strengths is the ability to help materials companies develop materials quickly and efficiently.”

Xaar’s 2020 Vision

“Xaar’s 2020 vision is pretty clear and that’s to double revenue,” Hopkinson said. “To double revenue, you’re going to have to do it by inorganic means.” To do this, Xaar will explore acquisitions and partnerships, which the company has already been engaged in. For instance, in 2016, Xaar acquired Vermont-based EPS, which develops bespoke printing solutions.

In terms of partnerships, Xaar is working with Ricoh to create a thin film piezo printhead. Interestingly, Ricoh has begun selling a brand of SLS machines. This doesn’t meant that the company will develop its own HSS systems, but it may not be out of the question.

A third strategy for meeting its 2020 vision is to target the fast growing sector of 3D printing through the creation of Hopkinson’s 3D printing department. If this division is successful, it’s possible that HSS, as well as other new inkjet technologies, will proliferate and become integrated into mainstream manufacturing.

A shoe with a heel made with HSS. (Image courtesy of Loughborough University.)
A shoe with a heel made with HSS. (Image courtesy of Loughborough University.)

“Xaar’s heritage is in high volume industrial printing systems for everyday products like bathroom tiles,” Hopkinson said. “It makes sense for us to build on this heritage and enable high volume 3D printing; I expect HSS to displace a modest but financially significant share of the current injection molding and CNC machining markets.”

Through Xaar’s flexible model of AM development kits and HSS-specific services, MJF may find itself quickly surrounded by a number of different inkjet and sintering technologies. The result for the 3D printing industry could mean that the day of AM as a mass manufacturing technology may be just around the corner. 

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