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NEWS
New Technology For 3D Gloss Printing
December 30, 2020

Shape, color, and gloss.

Those are an object’s three most salient visual features. Currently, 3D printers can reproduce shape and color reasonably well. Gloss, however, remains a challenge. That’s because 3D printing hardware isn’t designed to deal with the different viscosities of the varnishes that lend surfaces a glossy or matte look.

According to information, Massachusetts Institute of Technology (MIT) researcher Michael Foshey and his colleagues may have a solution. They’ve developed a combined hardware and software printing system that uses off-the-shelf varnishes to finish objects with realistic, spatially varying gloss patterns. Foshey calls the advance “a chapter in the book of how to do high-fidelity appearance reproduction using a 3D printer.”

He envisions a range of applications for the technology. It might be used to faithfully reproduce fine art, allowing near-flawless replicas to be distributed to museums without access to originals. It might also help create more realistic-looking prosthetics. Foshey hopes the advance represents a step toward visually perfect 3D printing, “where you could almost not tell the difference between the object and the reproduction.”

Foshey, a mechanical engineer in the MIT Computer Science and Artificial Intelligence Laboratory (CSAIL), will present the paper at next month’s SIGGRAPH Asia conference.

The state-of-the-art way to reproduce a surface with spatially varying gloss is labor-intensive: The object is initially printed with high gloss and with support structures covering the spots where a matte finish is ultimately desired. Then the support material is removed to lend roughness to the final surface. “There’s no way of instructing the printer to produce a matte finish in one area, or a glossy finish in another,” says Foshey. So, his team devised one.

They designed a printer with large nozzles and the ability to deposit varnish droplets of varying sizes. The varnish is stored in the printer’s pressurized reservoir, and a needle valve opens and closes to release varnish droplets onto the printing surface. A variety of droplet sizes is achieved by controlling factors like the reservoir pressure and the speed of the needle valve’s movements. The more varnish released, the larger the droplet deposited. The same goes for the speed of the droplet’s release. “The faster it goes, the more it spreads out once it impacts the surface,” says Foshey. “So we essentially vary all these parameters to get the droplet size we want.”

The printer achieves spatially varying gloss through halftoning. In this technique, discrete varnish droplets are arranged in patterns that, when viewed from a distance, appear like a continuous surface. “Our eyes actually do the mixing itself,” says Foshey. The printer uses just three off-the-shelf varnishes — one glossy, one matte, and one in between. By incorporating these varnishes into its preprogrammed halftoning pattern, the printer can yield continuous, spatially varying shades of glossiness across the printing surface.

This work was supported by the National Science Foundation and the European Research Council.


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