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Virtual-reality-based simulation of NC programs for milling machines

: Neugebauer, Reimund; Klimant, Philipp; Wittstock, Volker


Bernard, A.:
Global Product Development. Proceedings of the 20th CIRP Design Conference : Ecole Centrale de Nantes, Nantes, France, 19th - 21st April 2010
Berlin: Springer, 2011
ISBN: 3-642-15972-9
ISBN: 978-3-642-15972-5
ISBN: 978-3-642-15973-2 (eBook)
International Academy for Production Engineering (CIRP Design Conference) <20, 2010, Nantes>
Fraunhofer IWU ()
Beschreibungssprache; Betriebstechnik; CAD-Konstruktion; CNC-Maschine; Datenumsetzung; Freiformfläche; numerische Steuerung; Prozessdaten; Virtuelle Fertigung; virtuelle Prototypentwicklung; virtuelle Realität

In production engineering, particularly for the work processes performed by machine tools, NC programs have become the established standard description language. In simple and clearly-structured NC programs, a test for errors and collisions could still be performed manually by the machine operator. However, with ever more complicated work piece geometries (especially for free-form surfaces), this was no longer possible without a great deal of effort, since most NC programs are automatically generated and contain several hundred thousand lines of NC code. Hardware in the Loop coupling between a real NC control unit and a virtual machine model, as presented here, enables early testing of the generated NC program. Since it is directly run on the same NC control unit on which it will subsequently also process data, additional possible sources of error are minimized. This is an enormous advantage in comparison to standard desktop-based simulation programs. The immersive VR (Virtual Reality) visualization of the machine tool further simplifies the recognition of possible course errors. Then, the removal simulation culminates in the CAD export of the virtually produced work piece, along the chain, CAD->VR->aAD. This tool permits testing of the resultant geometry, even prior to the production of the actual work piece. Further potential errors which can be detected early and remedied using this simulation include: problems resulting from the postprocessor, collisions between machine axes, and erroneous coordinates, such as destination points which the machine cannot reach due to its construction. In addition, temporal optimization of the NC program is possible. There is a need for research regarding the integration of multi-body systems into the simulation, including the calculation of movable masses on the machine as well as their static, dynamic stiffness and the return of the results to the NC control unit as current actual values. The continuing evolution of computing technology with ever-higher performance levels will enable the inclusion of the machine's process parameters in the simulation. This expansion could encompass the inclusion of repulsion forces and possible tool wear, and the prediction of tool breakage. In addition, the elastic re-shaping of the work piece (as well as the tool), dependent on relevant material parameters, could be simulated in real time. However, the risk remains that with the inclusion of all the process parameters described, useful data handling would no longer be possible. Therefore, the primary factors that are significant in the production process must be ascertained, in order to include only these in the initial simulation. The Hardware in the Loop coupling of a real NC control unit with a virtual machine model, as described in this paper, forms a suitable basis for the integration of additional functionalities in order to make a more realistic VR-based simulation possible.