01/2007 | Credible Inspection

Metal objects that tool machines mill from a steel block or weld together in a matter of seconds must then be inspected at an equally fast pace for correct shape and dimensions. The quality control is placed directly after the production process for short reaction times. The demanded resolution of the optical sensor is a hundred or a thousand times higher than for a sliding calliper. It inspects geometric shapes, such as planes, cylinders or cones with tolerances of less than one micrometer.

Working with industrial partners, Bosch researchers have developed a noncontact, optical measuring process that scans component surfaces with a thin light beam. Using fiberglass optics, this light beam is guided across the component, and infrared light reflected by its surface is guided back to the analyzer. In the analyzer, an interferometric measuring principle is used to measure the distance between the light beam and the surface, with a depth resolution slightly greater than one nanometer. To check its shape, the component is moved past the system optics. The scanning light beam even probes previously inaccessible areas of complex geometries — for special applications its diameter can be reduced to 35 micrometers, so it can measure minute cavities and holes.

Production engineers can use several hundred thousand measuring points per component to reconstruct the scanned product on the computer and detect deviations from specified shapes and dimensions. Working with mechanical engineering firms, Bosch researchers have integrated the WhitePoint optical scanning system into several measuring machines, for measuring precision components with tolerances of less than one micrometer and for improving production processes.