Beitrag (Sammelband oder Tagungsband)
Anton Schmailzl, S. Steger, M. Dostalek, S. Hierl
Online process monitoring at quasi-simultaneous laser transmission welding using a 3D-scanner with integrated pyrometer
Proceedings of SPIE 9736: SPIE LASE (13-18 February 2016; San Francisco, CA, USA)
Quasi-simultaneous laser transmission welding is a well-known joining technique for thermoplastics and mainly used in the automotive as well as in the medical industry. For process control usually the so called set-path monitoring is used, where the weld is specified as "good" if the irradiation time is inside a defined confidence interval. However, the detection of small-sized gaps or thermal damaged zones is not possible with this technique. The analyzation of the weld seam temperature during welding offers the possibility to overcome this problem. In this approach a 3D-scanner is used instead of a scanner with flat-field optic. By using a pyrometer in combination with a 3D-scanner no color-corrected optic is needed in order to provide that laser- and detection-spot are concentric. Experimental studies on polyethylene T-joints have shown that the quality of the signal is adequate, despite the use of an optical setup with a long working distance and a small optical aperture. The effects on temperature are studied for defects like a gap in the joining zone. Therefore a notch was milled into the absorbent polymer. In case of producing housings for electronic parts the effect of an electrical wire between the joining partners is also investigated. Both defects can be identified by a local temperature deviation even at a feed rate of four meters per second. Furthermore a strategy for signal-processing is demonstrated. By this, remaining defects can be identified. Consequently an online detection of local defects is possible, which makes a dynamic process control feasible.
M. Dostalek, S. Steger, Anton Schmailzl, S. Hierl
Detecting Defects Reliably. Pyrometer-Based Temperature Measurement during Quasi-Simultaneous Laser Transmission Welding.
Kunststoffe International, vol. 105, no. 12, pp. 37-40
The integration of a broadband pyrometer in a 3-D scanner enables a continuous and local temperature measurement during the quasi-simultaneous laser transmission welding process. Welding tests on polyethylene samples show that defects can be clearly identified based on the temperature signal, despite a high scanning velocity.