NONCONTACT ONLINE LAYER THICKNESS MEASURE MENT IN INDUSTRIAL COATING PROCESSES

A non-contact and non-destructive method for the measurement of the la yer thickness in an industrial coating process is described. The metho d is based on the time-resolved measurement of the temperature of the coated surface during and after the irradiation with a laser pulse. Th e measurement time of this photothermal technique is only several 10 m s for coating thicknesses in the order of 100 mu m, which is significa ntly shorter than the measurement with thermal waves. This enables the use of the technique even on moved objects without moving the measure ment system. The measurement is done on the wet paint and calibrated o n the thickness of the dry coating after stoving of the paint. The res olution related to the layer thickness after stoving is about +/-1 mu m for a thickness range from 10 to 100 mu m. The new measurement techn ique is able to measure the distribution of the layer thickness on the coated object just after paint application in order to optimize the p aint application process.