AUTOMATED RAPID METROLOGY FOR LARGE INVESTMENT CASTINGS

TO MEET EXISTING AND FUTURE CASTING MANUFACTURING NEEDS, THE DEVELOPMENT OF AN AUTOMATED RAPID METROLOGY (ARM) CAPABILITY FOR INVESTMENT CASTING LAYOUT IS BEING INVESTIGATED. THE APPROACH IS BASED ON THE EXTRACTION OF DIMENSIONAL INFORMATION FROM COMPUTED TOMOGRAPHY (CT) IMAGES OF A PART. A KEY ADVANTAGE OF ARM IS THAT IT RELIES UPON A RADIOGRAPHIC METHOD TO NONDESTRUCTIVELY OBTAIN BOTH EXTERIOR AND INTERIOR VIEWS OF THE OBJECT, ELIMINATING THE NEED FOR SECTIONING. A SECOND ADVANTAGE IS THAT SINCE CT IS A DENSITOMETRIC MODALITY, BOTH DIMENSIONAL AND DEFECT INFORMATION CAN BE OBTAINED SIMULTANEOUSLY. HOWEVER, THE MOST IMPORTANT ADVANTAGE OF THE PROPOSED ARM CONCEPT IS THAT CT SYSTEMS ARE ORDERS OF MAGNITUDE FASTER THAN ALTERNATE METHODS. A SINGLE CT SCAN SET CAN BE OBTAINED IN A FEW HOURS, PROVIDING COMPLETE DIMENSIONAL INFORMATION AND 100 PERCENT SCREENING FOR POROSITY AND MICROSHRINK DEFECTS, EVEN IN INACCESSIBLE REGIONS OF COMPLEX MULTIPLE-WALL SUPERALLOY CASTINGS. CORRECTIONS FOR PARTIAL VOLUME AND SCATTERED-RADIATION ARTIFACTS AND ALGORITHMS FOR THIN-WALL POROSITY DETECTION ARE BEING DEVELOPED AND IMPLEMENTED. THE EFFICACY OF THESE METHODS WILL BE EVALUATED ON HIGH-ENERGY CT DATA OF A LARGE STRUCTURAL SUPER-ALLOY COMPONENT.