Predicting thermal loading in NC milling processes

In dry NC milling, a significant amount of heat is introduced into the workpiece due to friction and material deformation in the shear zone. Time-varying contact conditions, relative tool–workpiece movement and continuous geometric change of the workpiece due to material removal lead to a perpetually changing inhomogeneous temperature distribution within the workpiece. This in turn subjects the workpiece to ongoing complex thermomechanical deformations. Machining such a thermally loaded and deformed workpiece to exact specifications may result in unacceptable shape deviations and thermal errors, which become evident only after dissipation of the introduced heat. This paper presents a hybrid simulation system consisting of a geometric multiscale milling simulation and a finite element method kernel for solving problems of linear thermoelasticity. By combination and back-coupling, the described system is capable of accurately modeling heat input, thermal dispersion, transient thermomechanical deformation and resulting thermal errors as they occur in NC milling processes. A prerequisite to accurately predicting thermomechanical errors is the correct simulation of the temperature field within the workpiece during the milling process. Therefore, this paper is subjected to the precise prediction of the transient temperature distribution inside the workpiece.