This Novel 3D Printing Resin Gives DLP Additive Manufacturing a New Trick: Subtraction

A team of researchers at the Lawrence Livermore National Laboratory (LLNL) and the University of California Berkeley has come up with a way to give resin-based additive manufacturing its biggest missing feature: the ability to subtract material, as well as add it — leading to a future where an error in a 3D print doesn't mean chucking it away and starting from scratch.

"Imagine if a company needed a part to fit a certain machine but it's a prototype and they're not quite sure what they want," explains LLNL scientist and co-author Benjamin Alameda of the team's work. "They could theoretically print with our resin. And if there were defects or something they wanted to change about it, they don't have to print a whole new part. They could just shine another wavelength on it and modify the existing part. That’s useful and less wasteful."

A resin-based digital light processing (DLP) 3D printer works via a repeated lithographic process: a resin that hardens under ultraviolet light is, most commonly, placed into a vat atop a liquid-crystal display with a UV backlight. The desired 2D pattern is shown on the screen, and a layer of the resin hardens before a print surface raises up and the next layer is displayed. Repeat enough times, and you've got a 3D object.

The problem here — and the same is true for filament-based deposition printers — is that there's no way back: the printer can print, but it can't un-print. That's where the LLNL researchers come in, with a new form of resin that responds differently depending on the wavelength of light to which it's exposed: blue light hardens it, as with traditional UV-cured resin, but ultraviolet light liquefies it again.

"Once we see there are printing errors, we can adaptively modify the projection images to correct those errors on-the-fly, which enables a true adaptive manufacturing," explains co-author Liliana Dongping Terrel-Perez of how the resin could be used to create additive-and-subtractive 3D printers. "Besides DLP printing, we are also planning to transfer this method to volumetric additive and subtractive manufacturing, which shines light to a rotating vial of resin and fabricates a 3D part all at once."

The team has published its work in the journal Advanced Material Technologies under closed-access terms; LLNL's Innovation and Partnerships Office is offering to license the technology, which has been patented in the US, and says it can be applied to existing 3D printers.