New volumetric 3D printing pushes boundaries of traditional AM limitations

Advancements in 3D printing markedly improved design capabilities as well as shrunk manufacturing time. However, the technology has generally been limited by layer-based printing methods, which, although faster than traditional methods, can take up to several hours to complete.

Volumetric 3D printing enables researchers to build complex 3D parts using hologram-like 3D images flashed into photosensitive resin. Photo courtesy of LLNL.

Researchers at Lawrence Livermore National Laboratory (LLNL), along with collaborators at UC Berkeley, the University of Rochester and the Massachusetts Institute of Technology (MIT) are working on a new 3D printing method to push the boundaries of this technology.

The team discovered what they call “volumetric” 3D printing, which allows them to build complex 3D parts in a fraction of the time of traditional layer-by-layer printing by using laser-generated, hologram-like 3D images flashed into photosensitive resin.  It also works better in zero gravity than traditional methods, expanding the possibility of space-based production.

“We’re trying to print a 3D shape all at the same time. The real aim of this paper was to ask, ‘Can we make arbitrary 3D shapes all at once, instead of putting the parts together gradually layer by layer?’ It turns out we can,” says LLNL researcher Maxim Shusteff, the paper’s lead author.

Schusteff explains that the process works by overlapping three laser beams that define an object’s geometry from three different directions, creating a 3D image suspended in the vat of resin. The laser light is kept on for about 10 seconds, enough time to cure the part. The excess resin is drained out of the vat and researchers are left with a fully formed 3D part.

This new method allows for parts to be built faster than most commercial AM options available and the team hopes this low-cost option will open up new research opportunities in rapid 3D printing.

“Most 3D printing and additive manufacturing technologies consist of either a one-dimensional or two-dimensional unit operation,” says LLNL engineer Chris Spadaccini, who heads Livermore Lab’s 3D printing effort.

One of the challenges with traditional 3D printing is designing objects that don’t sag without supports. Shusteff explains that volumetric printing has no such constraints—many curved surfaces can be produced without layering artifacts.

“This might be the only way to do AM that doesn’t require layering,” Shusteff said. “If you can get away from layering, you have a chance to get rid of ridges and directional properties. Because all features within the parts are formed at the same time, they don’t have surface issues.”

The team hopes that other researchers will take up the task finding ways to do this with other materials.

Shusteff believes volumetric printing could be made even faster with a higher power light source. Extra-soft materials such as hydrogels could be wholly fabricated, he said, which would otherwise be damaged or destroyed by fluid motion.

With all of the benefits, this new method has some limitations including restrictions on part resolution and types of geometries that can be formed. According to the team, extremely complex structures would require lots of intersecting laser beams and would limit the process.

“If you leave the light on too long it will start to cure everywhere, so there’s a timing game too,” Spadaccini adds. “A lot of the science and engineering is figuring out how long you can keep it on and at what intensity, and how that couples with the chemistry.”

www.llnl.gov