Influence of fibre orientation, tool geometry and process parameters on surface quality in milling of CFRP

Machining of highly abrasive carbon fibre reinforced polymer (CFRP) in the aerospace industry requires processes with excellent machining quality, sufficient tool lifetime and short cycle times. To reach these goals a detailed understanding of the physics of cutting and chip formation based on the tool geometry is necessary. This paper presents a fundamental study in milling of unidirectional CFRP focussing on variable process parameters, tool geometries and fibre orientations. A single-edged tool with cemented carbide inserts of variable macro geometry is utilised. The experiments are evaluated by 3D microscopy of the milled edges, detailed tool wear analyses and interpretation of cutting forces. The key conclusions from the experimental results are drawn to reach a better machining quality and increased tool lifetime. The delamination of top layer fibres from the ply below up to a certain distance from the milled edge, which depends on the forces at fibre cutting angle ϕ = 90°, has been identified as main quality issue. Force and tool wear models based on the measurement data are presented.