Automatic Blade Repair System Based on Reverse Engineering Strategies

The compressor and turbine blades of aircraft engines and gas turbines have to be overhauled at regular intervals. First, the worn out blades are welded manually or by a welding robot. After welding, the blades will normally be shaped by hand, using grinding bands. Automation of the shaping of the welded beads reduces costs and process time while giving higher accuracy and quality. The following repair technique has been found to allow automatic tooling of the weld on final domains of blades, via a chain of processes, which run on one, single standard, three axis machining center. 1) Digitization of blade cross sections below the welded bead; 2) Calculation of the nominal geometry of the final domains; 3) Calculation of the NC processing programs; 4) NC processing of the final domains of the blades. The complete repair for one blade (steps 1 to 4) takes two to three minutes. The 3D digitizing system captures the actual geometry and chucking position of the blades completely. Therefore, no CAD data or measuring data of a master piece are required and the free chucking position of the blades allows simple fixtures. The blades can be repaired without user interaction, individually or in a batch quantity.