Getting the wrinkles out of new cars.

Using light-emitting sensors to detect wrinkles as they begin forming in sheet metal during manufacturing processes could help automakers prevent such wrinkles and build better quality car parts with higher productivity and fewer mistakes. Yuan Zheng, professor of electrical engineering, Ohio State University, and graduate student Pratap Pereira successfully have tested the new technique using fiber optic and laser sensors.

Wrinkling is a common problem in a variety of processes where sheet metal is used, Zheng points out. When sheet metal is pushed into a die, the pressure on the metal has to be exactly correct. If it is too strong, the metal will tear; if too weak, the metal will wrinkle. Currently, manufacturers have to rely on trial and error to determine the correct pressure to use in a particular process. Even then, mistakes are routine.

"Our sensing process can monitor the status of sheet metal while it is actually being pushed into the die," Zheng indicates. "The sensors can detect wrinkles being formed before they can be seen and can adjust the pressure accordingly."

The researchers tested their technique using two different types of sensors. In one setup, two fiber optic sensors are used. Each emit a beam of light that strikes the sheet metal as it is being pushed into the die and is...