Abstract:
This study aims to develop tetrahedral amorphous carbon nanocomposite layer coated
tungsten carbide drill bits for single shot drilling of composite metal stack. Different coatings
were tested for hole integrity performance compared to an uncoated tool and the results were
validated using process capability six-pack analysis. The drilling process employed a 4.85 mm
twist drill with a feed rate of 0.05 mm/rev and spindle speed of 2600 rev/min. The experimental
results indicate that, all the coated tools produce H9 tolerance holes while uncoated tool
produced H7 tolerance holes with 18 % to 35 % better results. But statistical results show that all
the tools including uncoated tool require improvement to stay within the control limits. The hole
circularity error obtained by all the tools were below 24 μm in both the panels and is supported
by the statistical results as well. The uncoated tool exhibited 17.91 % better surface roughness in
aluminium panel compared to coated tools, while coated tools produced 17.2 % to 22.3 % better
surface roughness in composite panel. Statistical results suggested that, improvement is
necessary when drilling aluminium panel by all the tools while dopant added coated tools
produce better results in composite panel.
