Modelling, Simulation and Compensation of Thermomechanically Induced Material Deformation in Dry NC Milling Processes

Siebrecht, T.1, a; Wiederkehr, P.1, b; Zabel, A.1, c; Schweinoch, M.1, d; Byfut, A.; Schröder, A.2, e

1)
Institut für Spanende Fertigung, Technische Universität Dortmund, Baroper Str. 303, 44227 Dortmund
2)
Humboldt-Universität zu Berlin, Lehrstuhl für Mathematik, Rudower Chaussee 25, 12489 Berlin

a) siebrecht@isf.de; b) wiederkehr@isf.de; c) zabel@isf.de; d) schweinoch@isf.de; e) andreas.schroeder@mathematik.hu-berlin.de

Kurzfassung

During machining processes, a significant amount of energy is converted into heat at the point of contact of the machining tool and the workpiece. Throughout the process, the workpiece is thermally loaded, resulting in a complex and transient temperature distribution. The latter induces material deformations, which, when not considered in the planning of the machining process, may result in rejects of the manufactured part due to shape deviations or tolerance violations. Compensating thermally induced deformations in machining processes is a challenge for several reasons: The workpiece geometry itself is constantly changing due to the material removal process, which influences the heat flow and dispersion within the semi-finished workpiece. Due to the relative tool-workpiece movement and varying engagement conditions, the heat source changes with respect to location and magnitude, while the change of the surface area affects the cooling of the workpiece. The induced complex and inhomogeneous temperature field within the workpiece leads to an equally complex material response, which may lead to an erroneous material removal when finishing the workpiece in a thermally loaded state. As a result of the transient nature of the thermal loading and the induced deformations, an accurate compensation approach must take into account the specific time-dependent state of the workpiece for a particular engagement condition. For any non-trivial geometry, this requires the use of a simulation system. This paper presents a hybrid simulation system comprised of a geometric physically-based (GP) process simulation and a variation of the fictitious domain method in combination with a (higher-order) finite element (FE) method. The resulting FE simulation is used to predict the thermomechanically induced material response, while the GP simulation provides the appropriate boundary conditions. The hybrid simulation system is able to provide a detailed analysis of the transient in-process state of the workpiece, which forms the basis for avoiding or compensating an erroneous material removal. The simulation system and the compensation procedure are validated with machining experiments.

Veröffentlichung

In: Biermann D., Hollmann F. (eds) Thermal Effects in Complex Machining Processes. Lecture Notes in Production Engineering. Springer, Cham, (2018), S. 289-320, doi: 10.1007/978-3-319-57120-1_13