Simulation of the shrinkage behavior in Fused Deposition Modeling

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The aim of the project is to simulate the shrinkage behavior of components manufactured with Fused Deposition Modeling (FDM). By using the shrinkage simulation, the resulting dimensional change of FDM components shall be determined. By means of this dimensional change, optimized shrink factors are derived for the FDM process. These shrink factors are evidently responsible for a high dimensional accuracy. The shrink factor is a scaling along all axes to compensate the process-induced shrinkage of the plastic component. Preliminary investigations have shown that a globally adapted shrink factor (along the spatial directions X, Y and Z) can achieve a significant reduction in the occurring dimensional deviations of test specimens with a constant nominal length. Normally, there are different nominal lengths within a complex part. These nominal lengths can be small dimensions ≤ 10 mm or higher dimensions (≥ 100 mm).Whereas the optimized shrink factor is decisively dependent on the nominal length, a method shall be developed in the second step of the project how to apply locally adapted shrink factors already in the design and construction phase of the component. In order to be able to use the process for the production of individual and small series efficiently and economically, product requirements needs to be fulfilled already with the first component. Therefore, an operating point optimization is not desirable concerning the shrinkage factor, as this would increase the machine time and costs as well. In order to save resources, the shrinkage behavior of FDM parts should be analyzed with simulation technologies. Based on the findings optimum shrinkage factors for higher nominal lengths (up to 400 mm) or new materials, for example, are derived. Therefore, the cooling behavior is examined at a unit cell for determining the shrinkage, which represents the structure of a FDM part. Previously, it is necessary that the processing conditions are determined as well. These have a decisive influence on shrinkage. From the ascertained data of the melting and extrusion analysis, the input variables for the cooling simulation result. The main focus is on temperature and shrinkage simulation, with the aim of determining the resulting dimensional change.Finally, the simulation results are validated and evaluated by means of experimental investigations. The approach of locally applied shrink factors on specific geometries or nominal lengths of a complex demonstrator component has to be examined. Subsequently, the components are measured by means of a coordinate measuring machine and thus are analyzed with regard to the dimensional accuracy.