Complex hole shaping

A method for forming a cooling hole through a wall of a structure, the cooling hole having a diffuser with an outlet of a larger cross-sectional area on a first surface of the wall, the diffuser tapering to a smaller cross-sectional area within the wall, and the cooling hole having a through-hole extending from the smaller cross-sectional area to a second surface of the wall, the method comprising:

• first, drilling with an EDM tool an entry hole in the wall extending from the first surface to a location inside the wall;
• then, automatically forming with the EDM tool the diffuser starting at the location inside the wall and moving toward the first surface;
• and
• thereafter, forming with the EDM tool the through-hole.

A method of forming a cooling hole in an air-cooled component of a gas turbine engine, the component having a wall with an outer surface and an inner surface, the cooling hole having

• a diffuser portion extending between an outlet opening having a larger cross-sectional area on the outer surface and a smaller cross-sectional area location inside the wall portion, and
• an inlet portion extending between the smaller cross-sectional area location and an inlet opening on the inner surface, the method comprising:
• drilling with an EDM tool an entry hole from the outer surface to the smaller cross-sectional area location;
• then, forming the diffuser with the EDM tool by first removing material closer to the smaller cross-sectional area location and thereafter, removing material closer to the outlet opening on the outer surface, and
• thereafter, removing with the EDM tool material between the smaller cross-sectional area location and the inlet opening to form the inlet portion.