Manufacturing process combines advantages of 3D printing and injection moulding
With additive free-form casting, researchers at the Fraunhofer IPA (Stuttgart, Germany) devised a way to reduce the disadvantages of the widely used FLM (fused layer modelling) process. These disadvantages include suboptimal mechanical properties and high time expenditure. In addition, only certain materials, the so-called thermoplastics, can be processed with this method.
To eliminate these disadvantages, the researchers combined the additive process with a casting process. In the first step, the shell of the component is produced using the FLM process. The experts use the water-soluble plastic polyvinyl acetate (PVA) as the printing material. The cover is then automatically filled with a precisely metered amount of polyurethane or epoxy resin. With polyurethane, it only takes three minutes for the filling to dry. The component can then be extended to any height using the same principle. Once the process is complete and the component has cured, the mould is removed in a water bath. The result is a 3D-printed workpiece with properties similar to injection moulding.
The IPA researchers have installed a special dosing unit for two-component materials in the 3D printer to pour the filling material into the cover. This makes it possible to carry out the entire process, i.e. the pressure of the cover and the filling, “in one piece”. The printing process does not have to be interrupted and can be controlled completely digitized as with conventional 3D printing. In addition, two-component resins can be processed with this method. Heat-resistant thermosets can be used as building material. In addition, the component is assembled much faster. “All you have to do is print the shell and leave the rest to gravity,” says PA expert Jonas Fischer. Last but not least, the components are significantly more stable because the material completely fills the mould and thus no porosities or air inclusions occur.
The method is suitable for a wide range of applications and industries. “Electrically insulating components such as sockets can be produced with it. The process is also suitable for foams and cushions, such as those required for safety elements,” explains Fischer. In principle, combined free-form casting always brings advantages when large, complex components are required in small quantities. In addition, weight can be saved.
In a preliminary research project, the IPA researchers have successfully demonstrated the feasibility. In addition, various components were realized as prototypes. The researchers are now looking for industrial partners to support them in further developing the process to series production readiness. Material manufacturers who work with researchers to improve the properties of the two-component mixture are also in demand. Companies are also welcome to contribute ideas for various thermoset applications.
More information: https://www.ipa.fraunhofer.de/en.html
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