TOOL WEAR AND WORKPIECE SURFACE INTEGRITY WHEN HIGH SPEED BALL NOSE END MILLING HARDENED AISI H13

摘要

Experimental data and statistical analysis for the range of cutting parameters tested showed that: Tool wear was higher at the 60 deg workpiece angle, probably due to tool chatter and higher average cutting speeds / temperatures. All variable factors and interactions were significant for workpiece surface roughness which ranged from 2.2 - 10.7 mu m for R_z (0.36-2.18 mu m R_a). Surface roughness deteriorated when cutting speed was increased and feed per tooth decreased due to tool vibration. Surface roughness improved with an inclined workpiece due to the absence of cutting in the tool centre at 0 deg. No white layers or thermally affected zones were apparent below the machined surface in all the tests. No significant differences in workpiece microhardness between experiments performed at different cutting conditions occurred. All variable factors were significant for workpiece residual stress and increasing cutting speed and feed per tooth caused the compressive stresses to decrease probably due to an increase in thermal effect on the workpiece. With the 60 deg workpiece angle, the compressive stress decreased due to the absence of the rubbing effect of the centre of ball nose end mill.