Until now, resin-based 3D printing required the attachment of cumbersome support structures in the workpiece. These supports have several disadvantages. On the one hand they require additional planning measures in the CAD design, on the other hand the support structures have to be removed after printing. This causes manual work steps and avoidable waste.
Therefore, researchers at the Fraunhofer ILT developed the "TwoCure" process, in which liquid resin is applied layer by layer to already cured resin. Like a video projector, an LED exposure unit projects the layer geometry of the component into the liquid resin bath, which cures at the exposed points. The other resin areas are solidified by cooling, allowing the cured structures to float in the entire volume without support. Thus, the entire 3D construction volume and not just the construction platform of the machine can be used for the production process.
The developers rely on the interplay of light and cold: the component is cured chemically by light and the surrounding material is solidified thermally by cold. "The material is applied in a warm state and then cured irreversibly by light," says Holger Leonards, project manager for TwoCure at the Fraunhofer ILT. "At the same time, the cooled machine ensures that the component, which is produced in layers, freezes into a block together with the resin, which solidifies into wax. It can then be liquefied at room temperature so that the supporting material flows off. Only the 3D-printed components remain, which are only washed briefly and then hardened.