T700 Cutter Life Improvement Program.

Abstract : The purpose of the T700 Cutter Life Improvement Program was to reduce the number of cutters used for the blisk and impeller airfoil milling operations from 134 to less than 90 cutters per engine set, thereby reducing T700 engine cost. The objective was achieved by stiffening toolholders, improving cutter designs, and changing cutter material. Other parameters investigated include cutting speeds, cutting fluids, surface coating, and surface treatment of the cutters. Phase I of the program was mainly analytical, phase II involved more extensive laboratory testing of cutter designs, materials, cutting fluids machining parameters, and production verification of the laboratory results. A computer simulation program was used to study effect of spindle and tool compliance and eccentricity, cutter geometry, and cutting parameters on cutting forces and tool deflections. This is the first computer simulation program to accurately predict milling forces and tool breakage when tool deflection is significant. Cutter failure investigation was conducted to understand modes/causes of tool failure. As a result, adjustments to NC program were made, deficiencies in the cutter geometry were corrected to improve cutter life. Originator-supplied key words include: Airfoil milling, Milling cutters, Cutter inspection, BLISK, Five-axis milling, Impeller, Axial compressor, Cutter life, Basic computer program, Computer simulation.