Determination of Cutter Trajectories for Contoured Turbine Buckets

The advent of numerically controlled machine-tool systems introduces the serious problem of suitably employing them for part fabrication. To numerically contour the complex surface of a large turbine bucket with this type of machining system, it is necessary to determine the geometrical constraints on the motion of the cutter, which will sweep out the desired part surface as an envelope of the cutter surface. A definition of the turbine-bucket surface is given in terms of unequally spaced cross sections along the length of the part, and an interpolating procedure is employed to define the entire surface with properly faired transitions between the specified cross sections. The procedures outlined in this paper have been used to program an IBM 704 computer for the preparation of digital control tapes, which instruct the motions of the machining system.