DETECTION BY AUTOMATIC GAIN CONTROL FEATURES OF GRADUAL CUTTING TOOL BREAKAGE

• Main Authors: JAMES FREDERICK BEDARD, CHARLES EDMUND THOMAS, DOUGLAS GLENN WILDES, LAWSON PARKS HARRIS, STEVEN ROBERT HAYASHI
• Format: Patent
• Language: English
• Published: 01.05.1991
• Subjects: COMBINATIONS OR ASSOCIATIONS OF METAL-WORKING MACHINES, NOTDIRECTED TO A PARTICULAR RESULT; CONTROL OR REGULATING SYSTEMS IN GENERAL; CONTROLLING; DETAILS, COMPONENTS, OR ACCESSORIES FOR MACHINE TOOLS, e.g.ARRANGEMENTS FOR COPYING OR CONTROLLING; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MACHINE TOOLS; MACHINE TOOLS IN GENERAL CHARACTERISED BY THE CONSTRUCTION OFPARTICULAR DETAILS OR COMPONENTS; MEASUREMENT OF MECHANICAL VIBRATIONS OR ULTRASONIC, SONIC ORINFRASONIC WAVES; MEASURING; METAL-WORKING NOT OTHERWISE PROVIDED FOR; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS ORELEMENTS; PERFORMING OPERATIONS; PHYSICS; REGULATING; TESTING; TRANSPORTING

A tool break detection system has an automatic gain control to adjust the analog signal channel gain and hold the cutting vibration signal at a desired average level. The AGC time constant is long enough that the detection of abrupt tool breaks and sudden large signal level transistions by the digital signature recognition logic is unaffected. However, the gradual decrease in signal level produced by a crumbly-type break would be removed by AGC action. In a system with a hardware AGC, crossing a high gain threshold resets gain to a low value and the resulting abrupt and persisting change in signal level is detected by the abrupt tool break logic. Another embodiment uses the gain command output by a software AGC and generates a break detected signal directly, without resetting the gain command, as gain rises above a high gain alarm level which is recalculated at the start of each cut.