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As early as 2017, engineers at the Applied Photonic Devices Laboratory (LAPD) of the EPFL School of Engineering designed a 3D printer that could make objects almost instantly. Five years later, the team improved their printing equipment and methods to produce objects made of opaque resin, which could not have been achieved before.

EPFL's 3D printer is one of the fastest in the world. Most 3D printers work by depositing materials layer by layer, a process known as adding material. EPFL uses the volumetric method, which pours the resin into the container and rotates it. Engineers illuminate the container from different angles so that when the energy accumulated in the resin exceeds a given level, it will solidify. This is a very accurate way to make objects at the same resolution as the existing 3D printing technology.

This volume method can be applied to almost any shape of object. It took engineers only 20 seconds to make a tiny statue of Yoda in Star Wars, while the traditional manufacturing process took about 10 minutes.

Light can solidify the resin by interacting with photosensitive compounds contained in the plastic. Engineers say the new method works only if the light passes through the resin in a straight line without deviating, while the light in the opaque resin does not travel smoothly. To this end, they designed a solution.

First, they use a camera to observe the path of light through the resin, and then adjust the calculation to compensate for the light distortion. They also programmed the printer to run the calculations and correct the light, which ensured that the machine reached the energy needed to solidify the resin in time. As a result, engineers were able to print objects in opaque resin with almost the same precision as transparent resin, which was a major breakthrough.

Next, engineers hope to be able to use the new method to print several materials at the same time and increase the printer's resolution from 1/10 mm to micron. (trainee reporter Zhang Jiaxin)