Additive manufacturing, also known as 3D printing, already presents a wide range of advantages for industry. IPA expert Jonas Fischer explains: »You enter the CAD data for a workpiece and receive a finished part.« Small batches, prototypes and individual pieces are all faster and more cost effective to manufacture than is the case with injection molding. Moreover, complex structures and integrated functionalities can be created. However, there are still some weak points.
Only three minutes to harden
With FLM (fused layer modelling) printing, the most widespread method, a nozzle deposits the printed material in parallel lines. This creates seams and porosities. Jonas Fischer adds: »The material is not completely in the form like it is when molded. This means that the component has worse mechanical properties.« Furthermore, during FLM processes the nozzle applies each layer individually. It takes a long time for a large component to be constructed. A third disadvantage is that only plastics that become soft when heated (called thermoplastics) can be used with FDM printing. Thermosets, which remain stable after hardening regardless of any heat administered, cannot be printed.
With additive freeform molding, researchers at Fraunhofer have now found a way to keep these downsides to a minimum. To do this, they combined the additive process with a molding procedure. The first step is to manufacture the shell of the part via the FLM process. The experts use polyvinyl acetate (PVA), a water-soluble synthetic polymer, as the printing material. Subsequently, the shells are filled automatically with a precisely dosed quantity of polyurethane or epoxy resin. With polyurethane, it only takes three minutes for the filling to be cured. Next, the number of components can be increased if desired. As soon as the process is complete and the part has hardened, the shape is removed and placed in a water bath. This creates a 3D-printed workpiece with the properties similar to those of an cast part.
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