Helical milling of CFRP–titanium layer compounds

Helical milling is used to generate boreholes by means of a milling tool being operated on a helical path into the workpiece. The bore diameter can be adjusted through the diameter of the helical path. In comparison to conventional drilling operations this process often results in lower burr formation and fiber delamination. Therefore helical milling is used in the aircraft industry for cutting composites and composite-metal compounds. One of these compounds, which is regarded as difficult to machine, is a layer compound consisting of unidirectional carbon fiber reinforced plastic (CFRP) and TiAl6V4. This paper presents the impact of the axial and tangential feed during helical milling on process forces and borehole quality is shown.