ONLINE QUALITY CONTROL OF LASER WELDING WITH LINE-SCANNING IR-DETECTION

Tönshoff, H.K. ; v. Alvensleben, F. ; Ostendorf, A. ; Hillers , O.

Laser Zentrum Hannover e.V., Germany

Within the last few years, laser welding has established itself in industry as a highly reliable process in sheet metal joining. To achieve constant-error free welding results, there is a need for online inspection of the laser process, in order to recognize bad seams as early as possible. Such systems have been developed in the last few years. Process monitoring has mostly been based on the evaluation on the radiation emitted during the welding. It is measured by special photodiodes with filters for selected wavelengths. These systems are able to detect errors by comparing the actual signal with a recorded reference signal, but it is almost impossible to recognize the type of error that occurs.
To obtain information wich helps to classify possible welding defects, additional sensoring is necessary. Within this paper, an approach to analyze the thermo-image of the area surrounding the welding seam is presented. The possibilities of recognizing some types of welding faults and the advantages of an one-dimensional image acquisition by an IR-line-array are shown.

Keywords : sheet metal welding, quality control , online process monitoring, IR-line-scanning