Simulation Approach for Considering the Thermal Effects of Cutting Fluid Use and Axis Movements in the Machine Tool Workspace via Coupled CFD Models

Advances in hardware performance and modern simulation software tools have enabled significant improvements in the capabilities and precision of machine tool thermal error simulations. This in turn allows for better predictions of thermal errors and more effective machine tool design optimization. One area, which still holds large uncertainties, is the workspace of machine tools, where moving assemblies, the cutting process, cooling systems and other support systems create highly dynamic situational conditions, which are hard to predict, model or even measure. To account for these situational thermal interactions in error compensation models, this paper presents a coupled CFD modeling approach, which computes realistic transient heat transfer coefficients (HTCs) for improved thermal FEM analyses. This new composite model includes a tool-adjacent model equipped with internal coolant supply and integrated linear axis movements. The second submodel considers forced convection from axis movements in the workspace, the air evacuation unit and also from the near-tool model. Subsequently, the steady-state tool-adjacent CFD model is integrated into the transient workspace CFD model by transferring flow velocities and volume fractions as boundary conditions. Steps three and four use the computed HTCs on the machine tool surface to simulate the resulting temperature and deformation fields. By combining all four models, the influence of different process scenarios on the resulting thermal error of the machine tool can be obtained. Initial simulations for selected load cases reveal load-dependent differences in the resulting HTCs and temperature fields.