Active chatter control system for long-overhang boring bars

Some machining processes, such as boring, have been historically limited by excessive bar vibration, often resulting in poor surface finish and reduced tool life, A unique boring bar system has been developed to suppress bar vibration, or chatter, during machining using active control technology. Metal cutting test programs have shown proven, repeatable performance on hard-to-cut, aircraft industry high-temperature nickel alloys as well as more easily cut carbon steels. Critical bar length-to-diameter (L/D) ratios, depths-of-cut, feed rates and cutting speeds far exceed those attainable from the best available passively-damped boring bars, This industry-ready system consists of three principle subsystems: active clamp, instrumented bat, and control electronics, The active clamp is a lathe-mountable body capable of supporting bars of varying sizes and articulating them in orthogonal directions from the base of the bar shank. The instrumented bar consists of a steel shank. standard insert head and imbedded accelerometers. Wire harnesses from both the bar and clamp connect to central electronics comprised of highly-efficient switched-capacitor amplifiers that drive the piezoelectcic actuators, sensor signal conditioning, a PC-based program manager and two 32-bit floating-point DSPs. The program manager code runs on the host PC and distributes system identification and control functions to the two DSPs, All real-time signal processing is based on the principles of adaptive Biter minimization. Ebr the described system, cutting performance has extended existing chatter thresholds (cutting parameter combinations) for nickel alloys by as much as 400% while maintaining precision surface finish on the machined part. Bar L/D ratios as high as 11 have enabled deep boring operations on nickel workpieces that otherwise could not be performed free of chatter.