Patent ID: 6251315
Filing Date: 2001-06-26
Classification: B23K

Abstract:
A method for disposing laser blocking material on the interior of an airfoil for blocking a beam of radiation from a laser during a laser drilling operation, the airfoil having passages at least one of which has a hydraulic diameter which is less than about forty (40) mils, comprising:forming a charge of laser blocking material that has a shear thinning characteristic that is greater than zero and that is a thermoplastic polymer formed of only carbon and hydrogen which is partially amorphous and partially crystalline such that the crystallinity is greater than forty (40) percent to diffuse the beam of radiation from the laser;disposing the laser blocking material in a chamber having a nozzle;flowing the laser blocking material from the chamber into the airfoil and through the passages which includes the steps of,forcing a portion of the laser blocking material through a nozzle from the chamber of material such that at least a portion of the material experiences shear thinning prior to the material entering the airfoil;transferring energy to the laser blocking material to raise the temperature of the laser blocking material above the melting point of the material prior to the material entering the airfoil;pressurizing the laser blocking material to a pressure that causes additional shear thinning as the material flows through said passage having a hydraulic diameter that is less than forty (40) mils;wherein shear thinning of the material decreases the viscosity of the laser blocking material as the material flows through small passages in the airfoil, thereby decreasing the pressure differential along the passage and between the exterior and the interior of the passage and wherein the decrease in viscosity from pressure through shear thinning decreases the need to decrease viscosity by heating the laser blocking material.