Feb 1, 2019 | By Thomas

Researchers at Lawrence Livermore National Laboratory (LLNL) and the University of California, Berkeley have unveiled a 3D printer that creates an entire object at once, rather than building it layer by layer as typical additive-manufacturing devices do.

Nicknamed the "replicator" by the inventors — after the Star Trek device that can create any object on demand — the 3D printer uses light to transform gooey liquids into complex solid objects in only a matter of minutes. In addition, it can create intricate objects that are smoother, more flexible and more complex than a traditional 3D printer. It does this by combining a standard projector and a rotating vial filled with a liquid that hardens when exposed to light.

Researchers used new 3D printing technology to create a model of Rodin's 'The Thinker.' CREDIT: UC Berkeley photo by Stephen McNally

"Basically, you've got an off-the-shelf video projector, which I literally brought in from home, and then you plug it into a laptop and use it to project a series of computed images, while a motor turns a cylinder that has a 3D-printing resin in it," said Hayden Taylor, assistant professor of mechanical engineering at UC Berkeley and senior author of a paper describing the printer, which appears online yesterday (Jan. 31) in the journal Science.

The new 3D printer was inspired by medicine’s Computed Tomography, where X-rays are projected into the body from all different angles to reveal the geometry of bones or tissues. Researchers reversed that principle - rather than measuring an object, they created one.

The 'Replicator' 3D printer. (UC Berkeley photo by Hayden Taylor)

Called Computed Axial Lithography (CAL), the process starts with a Computer-Aided Design (CAD) model. Researchers use projected photons to illuminate the syrup-like resin, creating a continuously shifting video of projections as the vial rotates. The projection is calculated at each angle, researchers run an optimization algorithm and the result is a series of images that appears as a rotating video projection that can be played at a rate adjusted to the rotation of the resin vial. Like a CT scan done in reverse, the projections combine to form a 3D object that is suspended in the resin. After several minutes, the 3D structure appears, the researchers stop the exposure and drain the uncured liquid, leaving only the finished product. By using a projector instead of multiple laser beams the researchers demonstrated they could shine 1,440 different projections (four beams per degree in 3D space) into the resin as it rotates.

The researchers formulated a thick, syrupy liquid that hardens into a solid when exposed to a certain threshold of light. (UC Berkeley photo by Stephen McNally)

The 3D-printing resin is composed of liquid polymers mixed with photosensitive molecules and dissolved oxygen. Light activates the photosensitive compound which depletes the oxygen. Only in those 3D regions where all the oxygen has been used up do the polymers form the "cross-links" that transform the resin from a liquid to a solid. Unused resin can be recycled by heating it up in an oxygen atmosphere, Taylor said.

So far, the team has created a number of different objects using the new printer, from a tiny model of Rodin's "The Thinker" statue to a customized jawbone model. Currently, they can make objects up to four inches in diameter.

"This is the first case where we don't need to build up custom 3D parts layer by layer," said Brett Kelly, co-first author on the paper who completed the work while a graduate student working jointly at UC Berkeley and Lawrence Livermore National Laboratory. "It makes 3D printing truly three-dimensional." The technology has the potential to transform how products from prosthetics to eyeglass lenses are designed and manufactured, the researchers say.

Importantly, it can also encase an already existing object with new materials. For instance, researchers placed a screwdriver shaft within the resin, then used their 3D printer to fabricate a handle.

UC Berkeley researchers used a new light-based 3D printing technique to add a handle onto a screwdriver shaft. (UC Berkeley photo by Stephen McNally)

“I think this is a route to being able to mass-customize objects even more, whether they are prosthetics or running shoes,” said Taylor. “The fact that you could take a metallic component or something from another manufacturing process and add on customizable geometry, I think that may change the way products are designed.”

Watch the video below that describes 3D printing with light:



Posted in 3D Printing Application



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