PRECISION INSPECTION SYSTEM FOR AIRCRAFT PARTS HAVING VERY THIN FEATURES BASED ON CAD CAI INTEGRATION/

In this paper, a precision inspection technique using CAD/CAI integrat ion is proposed for parts having very thin and sharply curved features . The technique begins with feature reconstruction of turbine blades w hich have combined geometry, such as splines, and thin small radius ci rcles. The alignment procedures consists of two phases - rough and fin e phases: the rough phase alignment is based on the conventional 6 poi nts probing on the clear cut surfaces, and the fine phase alignment is based on the initial measurement of the curved parts using the least- squares technique based on iterative measurement feedback. For the ana lysis of profile tolerance of parts, the actual measured points are ob tained by finding the closest points on the CAD geometry by the subdiv ision technique developed. The Tschebyscheff norm is applied iterative ly, giving an accurate profile tolerance. The inspection technique dev eloped is applied to practical blade manufacturing, and has demonstrat ed good performance.