Northwestern researchers unveil HARP 3D printer with record-breaking throughput

The large-format, high-speed 3D printing technology is nearing commercialization

Researchers from Northwestern University have been developing a stereolithography-based 3D printing technology that is capable of incredibly high throughputs and large scale prints. Now, the team has unveiled its technology—called HARP (High-Area Rapid Printing)—and revealed that it is just 18 months away from commercializing it.

At 13 feet in height, the HARP 3D printer towers over people. But it is not only its size that is impressive: it can reportedly achieve print rates of up to half a yard (about 45 cm) per hour hour. This means it can produce an object the size of an adult human in just a couple of hours. Alternately, the speed and print bed size (2.5 square feet) can enable users to print many small parts at once, dramatically speeding up print job turnarounds.

“3D printing is conceptually powerful but has been limited practically,” commented Chad A. Mirkin, George B. Rathmann Professor of Chemistry in Northwestern’s Weinberg College of Arts and Sciences and director of the International Institute of Nanotechnology. “If we could print fast without limitations on materials and size, we could revolutionize manufacturing. HARP is poised to do that.”

The large-format HARP 3D printing process (Photo: Northwestern University)

A closer look at HARP

The innovative HARP technology is based upon a new patent-pending version of stereolithography, which uses a vertical printing approach and projected ultraviolet light to cure liquid resins. The technology also enables the printing of multiple materials, including rigid photopolymers, flexible materials and even ceramics.

But how has the technology managed to surpass existing SLA systems in terms of volume and speed? The answer is interesting.

Many resin-based 3D printers are limited by heat generated during the printing process, which can lead to extremely hot surface temperatures and cause printed parts to deform or crack. Typically, the faster the 3D printer operates, the more heat is generated, which means that existing systems have been inclined to stay small and have limited speeds.

“When these printers run at high speeds, a great deal of heat is generated from the polymerization of the resin,” explained David Walker, a researcher in Mirkin’s lab. “They have no way to dissipate it.”

With HARP, however, the researchers found a way around the heat problem by using a nonstick liquid that reportedly acts like liquid Teflon. The liquid is designed to flow over the projection window that the UV light passes through to cure the resin, removing heat and then circulating it through a cooling unit.

“The interface is also nonstick, which keeps the resin from adhering to the printer itself,” added James Hedrick, a researcher in Mirkin’s lab. “This increases the printer’s speed by a hundredfold because the parts do not have to be repeatedly cleaved from the bottom of the print-vat.”

3D printed part made from flexible material (Photo: Northwestern University)

Commercialization on horizon

The HARP 3D printing technology is reportedly nearing commercialization, with Mirkin estimating it could happen in as little as 18 months. When this happens, the researchers believe the technology will unlock all kinds of applications for 3D printing, especially for large batches of both large-scale and small-scale parts.

“When you can print fast and large, it can really change the way we think about manufacturing,” Mirkin said. “With HARP, you can build anything you want without molds and without a warehouse full of parts. You can print anything you can imagine on-demand.”

As a large-format 3D printer, HARP stands out for its ability to produce high-resolution parts that do not require extensive post-processing. That is, most large-format machines on the market print large parts with lower resolutions (for speed) and thus require extensive sanding or post-processing.

Because the 3D printer can produce robust components made from a variety of materials, it could have applications in a number of industries, including aerospace, automotive, dental, medical, fashion and more.

HARP can 3D print ceramic objects (Photo: Northwestern University)

“Obviously there are many types of 3D printers out there—you see printers making buildings, bridges and car bodies, and conversely you see printers that can make small parts at very high resolutions,” Walker added. “We’re excited because this is the largest and highest throughput printer in its class.”

Interestingly, this is not the first foray that Mirkin has had in the printing world. In 1999, he is credited with having invented the world’s smallest printer based on a novel technology called dip-pen nanolithography. The process, which first used a single tiny pen to pattern nanoscale features, eventually integrated an array of pens to channel light onto photo-sensitive materials. It was during the development of this technology that Mirkin first realized the benefits of using a nonstick interface.

A study detailing the HARP process was today published in the journal Science.

Tess Boissonneault

Tess Boissonneault moved from her home of Montreal, Canada to the Netherlands in 2014 to pursue a master’s degree in Media Studies at the University of Amsterdam. It was during her time in Amsterdam that she became acquainted with 3D printing technology and began writing for a local additive manufacturing news platform. Now based in France, Tess has over two and a half years experience writing, editing and publishing additive manufacturing content with a particular interest in women working within the industry. She is an avid follower of the ever-evolving AM industry.

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