In-Process Inspection Study (IPIS) for Abrasive Machining (Honing)

This study was to prove the feasibility of in-process inspection of parts being honed on the inside diameter. Capacitance and inductive eddy current sensors were bench tested for accuracy and for the sensitivities of these measurements to honing oil. Unlike capacitance sensing, eddy current sensing was insensitive to the oil, so a honing machine was set up that has two eddy current sensors diagonally opposed to each other in a fixture screwed to the honing head. The wires were fed through flexible coupling to a slip ring, where the signals were routed through a signal conditioner to a 12 bit analog voltage to digital conversion data acquisition board in a computer. A lookup table was automatically used to correct for deviations from linearity of the sensors. A color monitor enabled graphical displays of individual readings in real time. The data acquisition board introduced a plus or minus 0.0005 inch error from an 11 degree rotation between the readings of the two opposed sensors. Using truly differential gaging and sensors that match the full voltage range of the data acquisition board, more accurate roundness determinations could be made. Bench tests showed potentials of fiber optic and ultrasonic sensors to automatically measure surface finish of a wiped or coolant coupled part, respectively, on a honing machine and to detect large changes in surface finish in real time, as when a breaking stone would cause a flaw.