Product Code: ICAL06_310

Investigation into the Influence of Pulse Shaping on Drilling Efficiency
Authors:
Ken Watkins, University of Liverpool; Liverpool Great Britain
Martin Sharp, Lairdside Laser Engineering Centre; Liverpool Great Britain
Mohammed Naeem, GSI GROUP; Rugby Great Britain
Patricia Scully , School of Chemical Engineering and Analytical Science; Manchester Great Britain
Paul French, Lairdside Laser Engineering Centre; Liverpool YT Great Britain
Russell Goff, School of Chemical Engineering and Analytical Science; Manchester Great Britain
Presented at ICALEO 2006

Laser percussion drilling is now a well established material processing technique in the aerospace industry. These holes are important as they allow boundary layer cooling of the component. Of the two different drilling techniques, percussion and trepanning, percussion drilling is preferred as it allows the reduction in the cycle time of the component. This is a very important factor as some components can have up to 40,000 holes. One of the major aspects that concern the aerospace industry is the quality of the holes. Hole geometry such as taper, roundness and variation between holes must be within certain tolerances if the component is going to be used in an aero engine. Other important factors with respect to hole quality are metallurgical issues concerning recast layer and micro-cracking with in the hole. Using factorial experimental design a study was undertaken to look at various pulse shapes. An investigation into how the temporal shape of a drilling pulse interacts with other drilling factors was investigated. A sensor designed especially to measure the drilling velocity was used to determine the drilling efficiency of each laser drilling pulse. Interactions between the different pulse shapes and other important drilling parameters were also examined and best-drilling practices are discussed.