Method for producing hollow investment castings

摘要

A method for casting metering holes connecting the inner and outer surfaces of hollow investment cast objects, such as hollow air cooled gas turbine airfoils. The method incorporates mini cores having metering hole pins which extend further into the inner cavity than the surface of the cavity, so that the ends of the holes can be exposed by a subsequent machining operation. The method also includes forming a wax pattern which avoids contact between the wax and the metering hole pins so that the pins are not broken by the wax during the heatup portion of the wax removal step after formation of the ceramic casting mold.