Development of an automated ultrasonic inspection cell for detecting subsurface discontinuities in cast iron

Manufacturing of value added products by companies in todays global marketplace requires the vendors to meet certain minimum standards, SAE, ASTM, ISO, etc. In a global economy, as a manufacturer for the year 2000 and beyond, preferred vendors will become ISO 9000 certified to maintain a market share of produced goods. An automated inspection cell was developed for the inspection of cast iron ports to detect subsurface discontinuities. The cell consists of an ultrasonic flaw detector (UFD), transducer, robot, immersion tank, computer, and software. Normal beam pulse-echo ultrasonic nondestructive testing is performed on each rough casting. Using test blocks and castings supplied by an industrial partner and working with a skilled ultrasonic inspector; ultrasonic transducer selection, initial inspection criteria, and UFD setup parameters were developed the gray iron castings used in this study. The skilled ultrasonic inspector\u27s operation of the UFD was noted for development of the cell software. The ultrasonic inspection cell control software (UICCS) was designed and developed to perform the necessary functions for control of the robot and UFD in real-time. The UICCS performed two main tasks; emulating the manual operation of the UFD through the communication link with the unit, and evaluation of the ultrasonic signatures for detection of subsurface discontinuities. The next phase of the cell development involved the testing of a lot of 105 castings. These casting were processed through the inspection cell. The castings which passed the inspection criteria were returned to the manufacturer for machining into finished parts where they were visibly inspected for defects after machining. The castings that had ultrasonic signatures consistent with subsurface discontinues were manually inspected by the skilled ultrasonic inspector, with the manual inspection time recorded for comparison to the automated cycle time. The castings then were inspected using destructive testing techniques for detecting subsurface material voids. The developed automated inspection cell correctly classified the inspection locations 99.8% of the time. Compared to manual inspection (as measured in the study), the automated cell\u27s cycle time was 30 times more efficient