Dec 11, 2017 | By Benedict
With the help of academic collaborators, researchers at Lawrence Livermore National Laboratory (LLNL) are using hologram-like 3D images projected into photosensitive resin to 3D print complex parts in a very short time. The volumetric 3D printing process prints objects all at once, rather than layer by layer.
There are several distinct technologies that fall under the banner of 3D printing or additive manufacturing: FDM, SLM, SLA, etc. All of these very different 3D printing techniques process their respective materials in different ways, but they all share one key feature: they fabricate objects layer by layer.
LLNL, never an organization to shy away from rewriting the rulebook, has developed a holographic resin 3D printing technique which totally sidesteps the layer-by-layer approach to fabricating an object.
It’s called volumetric 3D printing, and it uses a kind of 3D hologram projector to cure light-sensitive resin in one go, rather than one layer at a time. The process has been developed in collaboration with researchers at UC Berkeley, the University of Rochester, and MIT.
According to the large group of researchers, the process of generating 3D light projections instead using a regular projector (2D) or a laser (1D) makes a big difference in how quickly you can 3D print a part.
The LLNL logo printed using volumetric 3D printing technology.
“This moves fabrication to a fully 3D operation, which has not been done before,” explains LLNL engineer Chris Spadaccini. “The potential impact on throughput could be enormous and if you can do it well, you can still have a lot of complexity.”
The process works by directing three overlapping laser beams that together can define an object’s geometry from three different directions. This results in a complete 3D image projected within the vat of resin.
Of course, light also touches parts of the resin that aren’t supposed printed, but because the light has much greater intensity where the beams intersect, around 10 seconds of beaming is enough to fully and accurately cure the 3D part. Unused resin can then be drained away, leaving the completed plastic part behind.
“The fact that you can do fully 3D parts all in one step really does overcome an important problem in additive manufacturing,” says LLNL researcher Maxim Shusteff, the paper’s lead author.
Shusteff and the other researchers think that, because volumetric 3D printing is so much faster than other polymer 3D printing techniques, it could open up a whole new subcategory of the 3D printing industry.
To prove their point somewhat, the 3D printing method has already been used to 3D print beams, planes, struts at arbitrary angles, lattices, and curved objects. And it’s these curved objects that are getting the LLNL team particularly excited: because of the nature of the process, curved surfaces can be produced with little to no layering artifacts.
The all-at-once process also allows parts to be 3D printed that might otherwise need a large support structure.
There are, however, a few limitations to the volumetric 3D printing process. Since the laser beams remain unchanged during the 3D printing process, part resolution is limited and very complex shapes are hard to fabricate. Furthermore, scientists need to better understand the chemistry behind curable resins to know, for instance, how long the laser should be beamed in each instance.
But these limitations are a minor inconvenience when compared to the huge opportunities presented by the new 3D printing process. The researchers think volumetric 3D printing could be used to create delicate hydrogel structures, and could even be used in zero-gravity conditions for in-space printing. Moreover, it’s simply very, very fast, and will only get faster with the use of higher-powered lasers.
Holographic volumetric 3D fabrication system schematic and example structures.
(A) SLM, liquid crystal on silicon spatial light modulator; FTL, Fourier transform lens; BB, beam block to eliminate undiffracted light; HP, hologram plane; 4fN, telescope lens pairs in the “4-f” configuration used for beam expansion or image relaying [4f2 incorporates a pinhole spatial filter (SF)]. The inset image details the configuration of 45° prism mirrors for directing image subcomponent beams at orthogonal directions into the resin volume. (B to G) Structures fabricated using this system, each from a single exposure of 5- to 10-s duration. Scale bars, 2 mm.
“I’m hoping what this will do is inspire other researchers to find other ways to do this with other materials,” Shusteff says. “It would be a paradigm shift.”
The research paper, “One-step volumetric additive manufacturing of complex polymer structures,” has been published in Science Advances. Its authors were Shusteff, Allison E. M. Browar, Brett E. Kelly, Johannes Henriksson, Todd H. Weisgraber, Robert M. Panas, Nicholas X. Fang, and Spadaccini.
Posted in 3D Printing Technology
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Not holography, sorry. The holography technique is totally diferent in concept and pratice.
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