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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Measurement and Modeling of Contact Forces during Robot-guided Drag Finishing

2021 , Uhlmann, Eckart , Kopp, Marco

Robot-guided drag finishing is a free abrasive grinding operation that is used for polishing and deburring of workpieces with complex shaped geometries. The workpiece is attached to a robot and moved through a bulk of abrasive particles. The motion of abrasive particles during contact with the workpiece is the basis of the material removal mechanisms. To investigate the motion of abrasive particles during contact, a force measurement system was used to determine contact forces. The experimental setup was replicated in a numerical simulation based on the discrete element method (DEM). Based on the comparison of experimental and simulative results the qualitative validity of the DEM model was concluded. With the presented DEM model, the characteristic particle behavior during contact with the workpiece can be modeled which allows the prediction of resulting processing marks. Consequently, the DEM model can be used to design free abrasive grinding operations without using the time and cost intensive trial and error approach.

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Prozessüberwachung durch Objekterkennung - Automatisierte Werkzeugverschleißmessung beim robotergeführten Gleitschleifen

2020 , Kopp, Marco , Uhlmann, Eckart

Die Werkzeuge beim Gleitschleifen sind Schleifkörper. Infolge ihrer Nutzung verschleißen die Schleifkörper, wodurch ihr Einsatzverhalten verändert wird. Zur Aufrechterhaltung gleichbleibender Bearbeitungsergebnisse sollte der Verschleißzustand daher regelmäßig überprüft und Schleifkörper gegebenenfalls gewechselt werden. In diesem Beitrag wird das Konzept eines Messsystems zur automatisierten Messung des Schleifkörperverschleißes vorgestellt. Der Einsatz des Messsystems kann zur Erhöhung des Automatisierungsgrades und somit der Wirtschaftlichkeit von industriellen Gleitschleifbearbeitungen beitragen. Insbesondere gilt dies für vollautomatisierte Prozesse wie dem robotergeführten Gleitschleif

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