HARP 3D printer set to ‘revolutionise manufacturing’

Researchers at Northwestern University have overcome issues around overheating to develop HARP, a 3D printer claimed to produce an object the size of an adult human in two hours.

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

Mirkin predicts that HARP, which is described in Science, will be available commercially in the next 18 months. David Walker and James Hedrick co-authored the paper.

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According to Northwestern, HARP prints vertically and uses projected ultraviolet light to cure the liquid resins into hardened plastic. This process can print pieces that are hard, elastic or ceramic. These continually printed parts are said to be mechanically robust and can be used in a wide range of products that include cars and aircraft.

A limitation of resin-based 3D printers is that they generate a lot of heat when running at fast speeds, leading to dangerously hot surface temperatures and potential cracks and deformations in printed parts.

“When these printers run at high speeds, a great deal of heat is generated from the polymerisation of the resin,” Walker said in a statement. “They have no way to dissipate it.”

The Northwestern technology bypasses this problem with a non-stick liquid that behaves like liquid Teflon. HARP projects light through a window to solidify resin on top of a vertically moving plate. The liquid Teflon flows over the window to remove heat and then circulates it through a cooling unit.

HARP’s size allows it to print large, continuous structure or many, different small structures at once (Image: Northwestern University)

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

“The interface is also non-stick, which keeps the resin from adhering to the printer itself,” Hedrick added. “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.”

Although 3D printing is transitioning from prototyping to manufacturing, current 3D printers’ size and speed have limited them to small-batch production. HARP is claimed to be the first printer that can handle large batches and large parts in addition to small 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 moulds and without a warehouse full of parts. You can print anything you can imagine on-demand.”

While other print technologies have slowed down or reduced their resolution in order to print large parts, HARP does not make such concessions.

“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 said. “We’re excited because this is the largest and highest throughput printer in its class.”

Furthermore, HARP uses high-resolution light-patterning to achieve ready-to-use parts without extensive post-processing. The result, the university claims, is a commercially viable route to the manufacturing of consumer goods.