On the optimisation of machining parameters for dry drilling of aeronautic aluminium alloy

Abstract
Machining aluminium alloys without lubrication seriously increases the tool wear because of the severe tribological conditions at the tool/chip interface. Indeed, metal cutting generates high temperatures and pressures due to the high strain rate ( 10⁴ s ^-1) and the friction between the tool and the chip. Thus, it is very important to be able to clearly identify the parameters influencing the machining quality. In order to study dry drilling with W-Co carbide tools, experiments were conducted using different drill geometries and varying cutting conditions. The workpiece material used in this work is the aluminium alloy 2024 T-351. Optimise drill geometries can be deducted from experimental results to obtain holes with an aerospace quality. The following parameters were used to evaluate the holes quality : the minimum and maximum diameter deviations, the burr height and the surface roughness. The microscope observation of the tool rake face shows that the main damage is adhesion and diffusion wear revealing the presence of high temperature. Cutting conditions were tested and chosen to limit the tool damage and by consequence to increase the tool life.