Northwestern University: Researchers Produce Large Scale 3D Printer & Control Heat with HARP Technology

3D printing technology is often seen from the ‘bigger is better’ perspective, especially as researchers and manufacturers continue to out-do each other in digital fabrication of enormous proportions. Now, a team at Northwestern University has created a large-scale, ‘futuristic’ 3D printer capable of printing a prototype or part that is the size of an adult human—and in just two hours.

Using high-area rapid printing (HARP), the research team has made enormous technological progress with throughput never seen before in on-demand manufacturing. And while historically 3D printing users want it all, there are usually numerous trade-offs with that ideal, including missing out on some of the advantages of such technology due to strength in one area and great loss in another—often at the risk of diminishing performance or quality or causing restrictions.

The researchers state that such compromises are not required with HARP technology, featuring a 13-foot-tall printer with a print bed measuring 2.5 square feet. The prototype—projected to be on the market in around 18 months—is currently able to print half a yard of material (whether single, large, or different parts at one time) in one hour, which the research team states is a record.

Chad Merkin (Photo: Northwestern)

“3D printing is conceptually powerful but has been limited practically,” said Northwestern’s Chad A. Mirkin, product development leader. “If we could print fast without limitations on materials and size, we could revolutionize manufacturing. HARP is poised to do that.”

This project evolved as chemists Joseph DeSimone and Mirkin, long-time friends, began working together in the 3D printing field in 2015. DeSimone and colleagues at the University of North Carolina in Chapel Hill wrote about continuous liquid interface production (CLIP). And while it has been groundbreaking, undeniably, CLIP technology still offers challenges in production also—notably during curing, causing warping and cracking, often due to size. Mirkin’s developers, working within their new company Azul 3D, have worked past such issues by circulating coolant beneath the resin, and then sending it through a unit made for cooling—literally ‘pulling’ the heat from printed parts. This has allowed researchers so far to print objects that are one square meter in cross-section—and over 4 meters high.

Using ‘tiling,’ the researchers use light positioned from four projectors sitting side-by-side during the new SLA process.

(A) A hard, machinable polyurethane acrylate part (print rate, 120 μm/s; optical resolution, 100 μm) with a hole drilled against the print direction. Traditional noncontinuous layer-by-layer printing techniques typically delaminate and fracture when drilled in this orientation. (B) A post-treated silicon carbide ceramic printed lattice (print rate of green polymer precursor, 120 μm/s; optical resolution, 100 μm) stands up to a propane torch (~2000°C). (C and D) A printed butadiene rubber structure (print rate, 30 μm/s; optical resolution, 100 μm) in a relaxed state (C) and under tension (D). (E) Polybutadiene rubber (print rate, 30 μm/s; optical resolution, 100 μm) returns to expanded lattice after compression. (F) A ~1.2-m hard polyurethane acrylate lattice printed in less than 3 hours (vertical print rate, 120 μm/s; optical resolution, 250 μm). Scale bars, 1 cm. (Image: ‘Rapid, large-volume, thermally controlled 3D printing using a mobile liquid interface’)

“Tiling, with our technology, is theoretically unlimited,” Mirkin says.

Converting liquid plastics into solid parts, HARP prints vertically, curing under UV light. Parts can be used in applications for the automotive industry, aerospace, dentistry, and different areas of medicine. More detailed information about their work has also just been published in the recently published ‘Rapid, large-volume, thermally controlled 3D printing using a mobile liquid interface.’

Most 3D printers generate an obvious amount of heat, which can be prohibitive in design on a larger scale. In this case, light is projected through a window, that allows for the removal of heat and circulation through the cooling unit.

The HARP system 3D prints vertically (Image: Northwestern Now)

“Our technology generates heat just like the others,” Mirkin said. “But we have an interface that removes the heat.

“When you can print fast and large, it can really change the way we think about manufacturing,” Mirkin also added. “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.”

3D printing varies from one extreme to another, which is one facet of this technology that makes it so exciting. One day you may be reading about 3D printing on the micro-scale or experimenting with nano-composites, and the next, learning about manufactures fabricating parts on the large scale.

What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.

(A) Stationary print interface. (B) Mobile interface. (C) Mobile interface with active cooling. Elapsed time between panels (left to right) is ~500 s; scale bars, 25 mm. Data and thermal color mapping correspond to movies S1 to S3. (Image: ‘Rapid, large-volume, thermally controlled 3D printing using a mobile liquid interface’)