Prediction of Shape Deviations in Face Milling of Steel

Abstract

From today's point of view the production of high precision parts still poses a challenge due to rising demands in geometric accuracy and productivity. Shape deviations mainly arise due to thermal expansions during cutting and machining induced residual stresses. The importance of residual stresses strongly increases when machining thin-walled components. As a consequence, in order to meet higher standards, the industrial manufacturing of such components will require predictive compensation strategies for the combination of thermal effects and residual stresses. This work presents a new concept for the development of such compensation strategies for face milling of steel. In this research the effects of machining induced residual stresses (source stresses) are described by effective source stresses. They can be calculated directly from the distortion of machined specimens and represent the distortion potential of the face milling process for a given set of machining parameters. For the first time a newly developed calculation method allows the inclusion of torsion source stresses responsible for a twist of the machined workpieces as well as bending source stresses in two directions. This procedure enables a full mathematical description of workpiece deformations due to source stresses. Numerical studies have proven a feasible utilisation of experimentally obtained source stresses as input for finite- element-simulations. Subsequently both mechanisms leading to shape deviations, thermal expansion and deformations due to residual stresses, are superimposed by combining results from source stresses simulations and simulations of a moving heat source representing the thermal input of the machining process.