Evaluation of robot-aided ultrasonic thickness measurement

Wall thickness can be measured ultrasonically and usually this is performed by manually placing a probe at various locations on the outer contour of a part. This operation requires a high degree of operator skill because the probe must be positioned precisely and placed normal to the part surface for accurate measurements. As a means of automating the measurement process and minimizing the effects of human variability, robot placement of the ultrasonic probe was evaluated. With an appropriate adapter, a robot was used to move the probe to several positions on a part, and repeated thickness measurements were made at each location. The standard deviation of the thickness measurement was estimated to be 0.032 percent (maximum) of the measured wall thickness, with 95 percent confidence. This includes the variability of the measurement device as well as the variability of probe placement. Based on this experiment, the robot was judged to be capable of performing the ultrasonic thickness measurements.