Overview of emission-based laser process sensing

Abstract

The air-borne acoustic and optical-wavelength electromagnetic emissions of laser welds were studied. A full matrix of travel speed and laser power settings were used to generate full and partial penetration bead-on-plate welds in cold-rolled low-carbon steel sheet metal. The magnitude of the light emitted from the weld area was found to vary with process parameters, exhibiting a local minimum for “moderately” full-penetration welds. On the other hand, the RMS magnitude of the air-acoustic energy was found to have a local maximum near moderate full-penetration conditions. The relationship between the optical and acoustic signals was also investigated. It was found that the acoustic signal was approximately proportional to the time derivative of the optical signal.The air-borne acoustic and optical-wavelength electromagnetic emissions of laser welds were studied. A full matrix of travel speed and laser power settings were used to generate full and partial penetration bead-on-plate welds in cold-rolled low-carbon steel sheet metal. The magnitude of the light emitted from the weld area was found to vary with process parameters, exhibiting a local minimum for “moderately” full-penetration welds. On the other hand, the RMS magnitude of the air-acoustic energy was found to have a local maximum near moderate full-penetration conditions. The relationship between the optical and acoustic signals was also investigated. It was found that the acoustic signal was approximately proportional to the time derivative of the optical signal.