Experimental investigation of micro drillability of aluminum sheet composites

Aluminium composites are widely used in sectors such as automotive, defence and structural engineering. In this thesis, experimental studies were carried out on the micro-drillability of aluminium composite panels formed by joining two 3105 series aluminium sheets with low density polyethylene (PE) in between. After micro drilling of aluminium-polyethylene composite panel (Al-PE), cutting forces, burr formation at the exit, diameter changes in micro drills and diameters of the holes drilled on the panel were investigated. The micro drilling test parameters were designed using Taguchi's L16 (4^2 2^3) orthogonal array with five control parameters. These are four levels of cutting speed (10 m/min, 20 m/min, 30 m/min, 40 m/min), four levels of feed rate (0.5 µm/rev, 1 µm/rev, 2 µm/rev, 4 µm/rev), two levels of tool diameter (0.7 mm, 1 mm), two levels of coating status (AlTiN coated, uncoated) and two levels of tool tip angle (100◦, 140◦). For the analysis of variance (ANOVA), the variations in maximum drilling force (Fz), maximum burr height and both drill tool and hole diameters were measured. The results showed that the drilling force was maximum when drilling through the aluminum sheet, while the drilling force was minimum when drilling through the polyethylene sheet. The drill bit angle is the most effective parameter on the drilling force. Drill diameter has the most significant effect on the change in tool diameter (26,15%), while the bit angle has an effect of 25,79% on tool wear. Drill diameter (36.67%) and cutting speed (25.15%) have the greatest effect on the change in hole diameter. Increasing the cutting speed and feed rate also decreased the hole diameter change. Among the drilling parameters, the effect of feed rate on hole diameter change is 16.13%. However, the effect of AlTiN coating is 12.38% while the effect of tool tip angle (0.64%) is negligible. The tip angle had the greatest effect (67.80%) on the burr height at the hole exit, and the AlTiN coating caused softening of the polyethylene in the middle layer of the composite and the resulting plastering caused an increase in the burr height at the hole exit.