Laser drilling of non-circular apertures

A method for forming a plurality of cooling apertures through a wall made of metal and having outer and inner surfaces, each of the apertures including a diffuser having longitudinally paced apart forward and aft edges and transversely paced apart first and second side edges, and which opens up and outward from a bottom of the diffuser to the first surface of the component wall, said method comprising the following steps for each aperture:

• A) laser machining the wall with a laser which produces a laser beam having a pulse rate and power to vaporize the metal;
• B) laser drilling a feed and centering hole with the laser beam on the first surface of the wall in about a center of the diffuser;
• C) traversing the laser beam latitudinally across the surface along the aft edge to the first side edge of the diffuser in a single pass starting at a longitudinally extending centerline of the diffuser and at an increasing rate of speed so that each beam pulse vaporizes the wall metal at a spot such that successive laser hit spots substantially overlap each other in decreasing amounts so that the pulses nibble out the metal to collectively form a continuous portion of a trench of decreasing depth below the surface;
• and
• D) traversing the laser beam latitudinally across the surface to the opposite second side edge of the diffuser in a single pass starting at the longitudinally extending centerline of the diffuser and at an increasing rate of speed so that each beam pulse vaporizes the metal at a spot such that successive laser hit spots substantially overlap each other in decreasing amounts so that the pulses nibble out the metal to collectively form a continuous remaining portion of the trench of decreasing depth below the surface.