May 2000

Thick and Thin

By Technology Review

To avoid rust or flaking, the paint on a car must have a thickness consistent to within a fraction of a millimeter. Auto makers test thickness by picking a sample car, waiting until it's dry, and hitting it with an ultrasonic pulse from a handheld meter. But that process is slow and expensive-and now its days may be numbered. DaimlerChrysler is testing a laser inspection technology that works on wet paint. Designed by Plymouth, Mich.-based Perceptron, the system spits out several hundred laser pulses one after the other. Each infrared burst produces an ultrasonic "ring" that is higher in pitch where the paint is thinner. One big advantage of this system is that the line can be stopped and a problem fixed before a hundred or more mis-painted cars have gone through drying ovens. The National Institute of Standards and Technology, which funded Perceptron's development work, estimates that the system could shave $50 off the cost of painting each car, saving the Big Three automakers hundreds of millions of dollars a year.