Methodology for a model-based control of the boundary zone properties during milling of Ti-6Al-4V

A significant influencing factor which determines the strength, lifetime and reliability of a component after machining is the residual stress state in the boundary zone. A reliable adjustment of this condition during machining is currently not possible. It is desired to control the milling process using a model-based approach in order to generate defined geometries and residual stresses in titanium components simultaneously. This paper focuses on the influence of the process parameters on the residual stress state during the finishing operation of Ti-6Al-4V. The residual stress state was measured by X-ray diffraction. During the process, the cutting forces and heat flow were measured. For mapping possible interactions and statistical influences, a statistically validated test plan was applied. The influence of the process parameters cutting speed, feed rate and axial depth of cut on the residual stress condition are shown. In order to take scattering material properties into account, the initial residual stress state and the material structure were determined by measurements prior to the machining process. In addition, the tool wear condition and the microgeometry of the tool are taken into account as an observable disturbance variable. These factors are analyzed with regard to the influence on the residual stress state.