At Delphi Automotive's Chassis Div. plant (Sandusky, OH), the inspection of automotive wheel spindle bearings used to be a slow and costly process. "We had people sitting in booths for three shifts around the clock, checking 100% of the parts," relates Bablu Ratnaparkhi, senior metallurgist, NDT, at the plant.
Workers relied on a magnetic particle inspection process, by which parts were magnetized and sprayed with a magnetic particle-based solution. Because particles accumulated in cracks or other surface flaws on the magnetized parts, the flaws could be visually detected when parts were inspected under a blue light. The 0.1-inch-deep keeper groove on each spindle bearing was particularly difficult to inspect, however, and small, hairline cracks in the groove area were often hard for workers to spot, Ratnaparkhi says.