An experimental investigation of micro-machinability of copper 101 using tungsten carbide micro-endmills

Abstract

This paper presents an experimental investigation of micromachinability during micromilling of oxygen-free high conductivity (OFHC), commercially pure copper 101 using tungsten carbide micro-endmills. The forces, surface roughness, tool wear, and burr formation are analyzed under varying cutting speeds ( 40 , 80 , and 120 m/min) and feed rates ( 0.75 , 1.5 , 3 and 6 μ m / flute ). The experiments included full-immersion cutting with 254 μ m micro-endmills with an axial depth of cut of 30 μ m . The variation of forces, surface roughness, and burr formation with wear progression is also studied. It was seen that the minimum chip thickness and associated ploughing/indentation effects induce erratic variations to micromilling forces at feed rates in the vicinity of edge radius of the micro-endmills. At larger feed rates, the micromilling forces resemble those of conventional milling in the presence of tool-tip runout. The surface roughness was observed to be nearly constant at feed rates up to 3 μ m / flute , and to increase with feed rate for larger feed rates. Unlike conventional milling, greatest tool wear was experienced at the lowest feed rate and lowest speed, and the lowest wear was seen at the highest feed rate. The main mechanism of wear was concluded to be attrition wear in its most basic form, whereby the tungsten–carbide grains on the cutting edges were dislodged from the cobalt matrix. The smallest top burrs were experienced at 40 m/min surface speed at higher feed rates. The lowest feed rate of 0.75 μ m / flute resulted in large burrs at any speed. Progressing wear was seen to induce an increase in forces, a reduction in surface roughness, and a strong increase in burr formation.