HIGH SPEED BALL NOSE END MILLING OF INCONEL 718 WITH VARIABLE TOOL GEOMETRY-EXPERIMENTAL AND FINITE ELEMENT ANALYSIS

摘要

The longest cut length (approx 200 m) was achieved using the medium' radial rake angle and 'high' primary relief angle. Higher cut lengths were achieved when using tool geometries which did not lead to chatter. Cutting forces (Fx, Fy and Fz) were generally in the range 100-250 N and forces tended to be lower in magnitude where chatter did not occur. Workpiece surface roughness values of <1 mu m Ra were achieved in all tests with both new and worn cutting tools. Values as low as 0.4 mu m Ra were possible. Machined surfaces had tensile residual stresses (typically 200-1000 MPa), however, subsequent work has resulted in the production of surfaces with highly compressive stresses. 2D FE modelling of the process indicated similar trends to the force signatures obtained in the experimental work. Industrial pre-production trials on a combustion chamber outer casing have proved that high-speed ball nose end milling is a feasible process for aerospace components.