Hole taper characterisation and control in laser percussion drilling

Small hole (< 1 mm diameter) drilling by lasers is widely applied in various manufacturing processes. Hole tapering is one of the inherent manufacturing problems associated with laser percussion drilling (multiple pulse drilling) whereby material is ejected in the form of molten droplets when a series of laser pulses are delivered to a point on a workpiece. This paper reports an investigation into the mechanisms of hole taper formation, its characteristics and the development of a taper control technique. A statistical modelling technique is used to characterise the parameter relationships during hole-taper formation. Laser beam inter-pulse shaping is used to control the hole-taper. Parallel holes are produced as a result of this new development.