Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Prediction of the Roughness Reduction in Centrifugal Disc Finishing of Additive Manufactured Parts Based on Discrete Element Method

2022 , Kopp, Marco , Uhlmann, Eckart

One major drawback of additive manufacturing is the poor surface quality of parts, which negatively affects mechanical and tribological properties. Therefore, a surface finishing is necessary in most cases. Due to a high material removal rate, centrifugal disc finishing is a promising mass finishing operation for an effective surface finishing of additive manufactured parts. However, due to machining the workpieces in a freely movable manner, the process is hardly controllable, and the process design is often based on time-consuming and cost-intensive trial-and-error approaches. Especially when it comes to the machining of complex-shaped workpieces, finishing results are barely predictable. Therefore, the aim of this study is to set up a numerical simulation of the centrifugal disc finishing based on the Discrete Element Method (DEM) to predict finishing results. A procedure to determine the required DEM input parameters is presented and the simulation was validated using a freely movable force sensor. The results of the finishing experiments with additive manufactured workpieces made of Ti-6Al-4V were correlated with the simulated results. The derived correlation was used to predict local differences in the roughness reduction, which occurred when finishing workpieces with a limited accessibility to the surface. As a result, it is concluded that the complex relationship between the type of media, the accessibility to the surface, and the achievable finishing results can be modeled using the DEM.

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DEM simulation of centrifugal disc finishing

2022 , Uhlmann, Eckart , Polte, Julian , Kuche, Yves , Landua, Fabian

The finishing of small components with complex geometries is a major industrial challenge. One process that is suitable for targeted post-processing is centrifugal disc finishing with wet and dry media. In this process, the workpieces float as bulk material together with the abrasive particles in a container and are completely surrounded by the abrasive medium. As shown in previous studies, the Discrete Element Method (DEM) is suitable for investigations of grinding processes with specified workpiece motions. To simulate unpredictable workpiece motion, a new approach is being tested in which the workpieces themselves are treated as particles. Within this research paper, results for the post-processing of centrifugal disc finishing with the software ROCKY DEM are presented. The investigation results show good correlation between the numerical determined pressures and the analysis results of the rounded workpiece edges on test components made of mould-steel X13NiMnCuAl4-2-1-1.

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Modeling of the wet immersed tumbling process with the Discrete Element Method (DEM)

2021 , Uhlmann, Eckart , Fürstenau, J.-P. , Kuche, Yves , Yabroudi, Sami , Polte, Julian , Polte, Mitchel

Immersed tumbling is an industrially established process for finishing of components made of metal, ceramic or plastic. In this process, the components are completely surrounded by a wet, abrasive medium, which allows burrs to be removed and surfaces to be polished. In order to gain specific insights into the influence and flow properties of the abrasive media used in this process, numerical approaches using the Discrete Element Method (DEM) with the Rocky DEM software are presented within these investigations. A complete process simulation could be realised by means of a digital machine tool. The immersed tumbling process with cone-shaped polymer abrasive media is implemented by use of a liquid bridge model. The results were validated by experiments with an industrially used immersed tumbling machine tool and for the first time allow sound statements about the contact conditions and interactions of the abrasive media with the workpiece.

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