Product Code: ICAL09_706

Welding Head for 'Self-Guided' Laser Welding
Authors:
Boris Regaard, Fraunhofer USA Center for Laser Technology; Plymouth MI USA
Stefan Kaierle, Fraunhofer ILT; Aachen Germany
Stefan Heinemann, Fraunhofer CLT; Plymouth MI USA
Rahul Patwa, Fraunhofer CLT; Plymouth MI USA
Jens-Peter Steinbrecher, Fraunhofer CLT; Plymouth MI USA
Presented at ICALEO 2009

Precise positioning of the laser beam on the work piece is crucial for high quality laser welds; e.g. for butt welding the focal point of the laser beam with respect to the joint must be maintained within an accuracy better than 20 - 150 µm, depending on the focused beam radius. These stringent accuracy requirements call for high precision robots, a repeatable work piece profile and precise clamping. To compensate for insufficient repeatability of work piece or clamping, seam-tracking devices are used. A sensor measures the joint position and computes a correction vector to follow the actual joint trajectory. The deviation is compensated either by robot trajectory adjustment or by an additional tracking axis. Disadvantages of this approach are complex installation of the devices due to interfacing with the robot control, the need of teaching and calibrating the sensor and principle based accuracy restriction that limit the usability in more complex 2d contours and with low accuracy robots.
We recently introduced a more flexible and precise approach that utilizes an advanced camera-based sensor that is capable of measuring seam position, relative displacement between work piece and sensor and melt pool of the process with one single device. This paper describes a realized 'self guided' welding head, which uses this approach in combination with an integrated high power scanner. The result is a welding head that follows a curved or linear butt weld with high precision and independent of the actual robot trajectory; without the need of calibration, robot interfacing and alignment. The welding head features an OAP optic with diffraction limited beam- and image quality and accepts any fiber coupled lasers source with up to 8 KW output power.