Recently, Fraunhofer IPA researchers have developed a new technology that combines 3D printing with casting. In AFFC, the shell of the first part is printed and manufactured by FLM process, and then it is filled with a two-component resin. This saves time, increases the stability of components and allows printing of new materials.
In the free addition casting process, part of the shell is printed by FDM and then filled with a mixture of two components. ©Fraunhoff
Additional material manufacturing, also known as 3D printing, has brought a wide range of advantages to industry. IPA expert Jonas Fischer explained, "You enter the CAD data of a workpiece and you get a printed part." Small batches, models and individual parts are manufactured faster and more efficiently than injection moulding. In addition, you can create some complex structures and integrate some functions together. Of course, there are also some shortcomings.
Curing takes only three minutes
FLM (Fused Deposition) process is the most widely used 3D printing process at present. This creates cracks and voids. Jonas Fisher added: "This material does not appear entirely in the form of a model. This means that the mechanical properties of the components are worse. In addition, nozzles are used in each layer in FLM process. It takes a long time to build a large component. The third disadvantage is that only plastics that become soft when heated (called thermoplastics) can be used for FDM printing. Thermosetting plastics cannot be printed.
Fraunhofer's researchers have now found a way to minimize these shortcomings. They combined the printing process with the forming process for this. The first step is to fabricate part shell through FLM process. Experts use polyvinyl alcohol (PVA), a water-soluble synthetic polymer, as a printing material. Subsequently, the shell is automatically filled with precise quantities of polyurethane or epoxy resin. With polyurethane, it only takes three minutes to complete. Next, you can increase the number of components if necessary. Once the process is completed and partially hardened, it is placed in a water bath. The performance of the 3D printing workpiece created in this way is similar to that of the casting.
Small parts manufacturing is possible
In order to inject filling material into the mould, IPA researchers installed a special two-component material batching unit in a 3D printer. This means that it is possible to complete the whole process - printing the shell and filling. Printing process does not need to be interrupted, and it can be completely digital controlled like traditional 3D printing.
IPA researchers have confirmed the feasibility of this process and created several prototypes.
In addition, the program allows the use of two-component resins. Heat-resistant sleeves can be used as building materials. And components can be manufactured faster. Jonas Fisher added: "You just need to print the shell - gravity can do the rest of the work." Finally, when the material is fully filled, the stability of these components will be greatly improved, so there will be no pore or pore.
This new method is suitable for various application fields and industries. Fischer explained: "For example, it can be used for electrical isolation components, such as sockets. For example, the foam and cushion needed for safety is also applicable to this process. In principle, when only a few batches of large and complex components are needed, the free addition casting process is preferred. In addition, it is also conducive to weight loss.