| An adaptive control constraint (ACC) system, developed and tested to obtain highly stable milling, regardless of varying cutting dynamics, is presented that eliminates chatter, when it arises, in most milling situations. It is a sensor-based system utilizing sound signals generated by the cutting process. The signals are detected by ordinary, condenser-type microphones. Modifications to, and extensions of, a previously developed algorithm, which regulates spindle speed to control chatter, are demonstrated that enhance the system's capability. Control is maintained by the generation of spindle-speed and table-feed override commands obtained from the analysis of sound signals. Speed adjustments achieve stability by either selecting a speed in a stable region between unstable lobes or lowering the speed to a point where process damping becomes effective. Table feed is adjusted accordingly to maintain a constant feed per tooth.; Isolation and filtering of the sound signal, coupled with better recognition of system instability, improve the ACC system's performance. Numerous low-speed cutting tests, using several types of tools on different materials, are presented to characterize process damping. Test results are shown that demonstrate the dependence of process damping on surface wavelength and workpiece material. System operation is illustrated for a variety of milling situations that involve both face- and end-milling operations on workpieces of different materials, with various tools and different machine configurations. Test results demonstrate the performance and limitations of the ACC system.; This system is particularly effective in eliminating chatter for high-speed, high-power milling. In addition, it easily interfaces with an existing, numerical-control (NC), milling machine. The adaptation of this system to current milling machines and to future, comprehensive-supervision, NC systems are suggested as logical extensions of this work. |
