What If 3-D Printers Had An “Undo” Button?

3-D printing used to be a fixed medium. Now, graduate students have created a printer that can go back in time, make changes on the fly, and best of all, build objects in a weightless environment. Here’s how it works.

True time travel may be a dream confined to Hollywood film scripts and Hermione Granger, but a group of grad students at the Southern California Institute of Architecture in Los Angeles have harnessed the ability to fix the past when it comes to 3-D printing. Traditional 3-D printers create objects by incrementally printing thousands of 2-D layers, which makes going back to fix things impossible. That’s why Brian Harms, the lead designer of the Suspended Dispositions project, and his team created a freeform printer that injects ultraviolet-curable liquid resin into a tank of gel using a needle-thin print head mounted on a robotic arm. The resin stays in liquid form until it comes into contact with UV light, which means designers can retrace missteps, manually or robotically, and fix potential design flaws. It’s essentially like pressing an “undo” button.

“You could go in with something like a syringe or metal needle and suck out the liquid resin that you injected, so you’re basically reversing the direction of the pump and retracing the tool path that you already traveled along,” says Harms. It’s even possible to “manually control where the robot is traveling so you could create an object that's only partially predesigned.”

The ability to “go back in print time” or control the printer manually is something traditional 3-D printers, which generate rigid structures to prevent objects from collapsing during the printing process, are unable to do. Instead of relying on solid supports, the gel substrate in the freeform printer acts as a “passive but omnidirectional support material,” according to Harms.

“The gel traps the resin in place and then once you've hardened the resin you can just pull your part out and leave the tank of gel there to be reused,” he explains.

Printing in a gel tank also means the robotic arm isn't restricted to working in skinny 2-D slices like traditional 3-D printers. This freedom of movement allows the printer to create more complex objects than normal printers because it can draw vector paths instead of traditional, layer-based contours.

“We have the ability to navigate around other objects inside of the gel,” Harms says. “We’ve 3-D printed a small ring in the gel and then had the robot print an interlocking ring around that existing object.”

The freeform printer isn’t just more flexible than its precise counterparts, it’s much faster as well. Harms and his team investigated by comparing how long it took their technology to create a wireframe cube compared to a traditional printer. Armed with the ability to print in vectors, Harm’s robot drew 12 lines suspended in the gel in 30 seconds, followed by a two-minute-long UV-curing process. A traditional printer would take around an hour to create the same product, although with superior resolution.

Harms and his team haven’t created any “real world” products with their printer yet, but he believes the technology has the ability to build more creativity into the 3-D printer production process.

“We’re interested in asking questions like, ‘What happens when you send a design to the printer and then step in and modify it on the fly, or remove parts you don’t like, or change the color of the resin?’” he says. The ability to create multiple connected objects within the same gel-space is another potential use of the technology, according to Harms.

“If you filled an entire room and had these robots submerged in the gelatin you could create much larger structures that could be architectural components.”

The emphasis of Harms and his team’s printer is focused on the rapid prototyping of structures, not product design or fabrication. But the team says the potential is much wider. Mataerial, a company currently experimenting with 3-D printing in space, is operating with the same design dream as Harms and his team: gravityless printing.

“It’s the idea we can do things without being constrained by support,” says Harms. “It can be more real time, immediate, and a direct output as opposed to a product that's been translated into machine code.”

Harms’ teammates include: Haejun Jung, Vince Huang, and Yuying Chen.