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Product Code: ICA13_1105

Detection and Repairing of Weld Defects
Authors:
Peter Berger, IFSW, University of Stuttgart; Stuttgart Germany
Timo Bauknecht, Ifsw, University of Stuttgart; Stuttgart Germany
Meiko Boley, Ifsw, University of Stuttgart; Stuttgart Germany
Felix Abt, Ifsw, University of Stuttgart; Stuttgart Germany
Rudolf Weber, Ifsw, University of Stuttgart; Stuttgart Germany
Thomas Graf, Ifsw, University of Stuttgart; Stuttgart Germany
Presented at ICALEO 2013

There are different strategies to react on a detected weld defect. A very expensive one is to check the generated weld seam after welding and to put the part back into the clamping device for a further weld, if the joint does not fulfill the requirements. If a joint is vulnerable to defects, this procedure results in high costs. Therefore, there are different approaches to inspect the weld seam during the welding process in an in-process or post-process monitoring. The inspection systems reach from single sensors to camera-based systems. Because of the high flexibility and small interfering contour coaxial systems are often preferred. Most of these systems can decide if there is a defect or not, but can’t obtain the shape and type of the defect.

As a result of the WELDone project (funded by German Federal Ministry of Education and Research), the Institut fuer Strahlwerkzeuge developed a camera system that uses two images on the camera chip, resulting from process emissions with different polarization orientations. With the aid of a fast FPGA (field programmable gate array) the orientation of the hot workpiece surface is obtained on-line. With this information attributes of several different weld defects can be recognized. In principle, it is even possible to reconstruct the topology of the surface and not only detect a defect, but also characterize it.

Since different defects require different treatments of the weld in a second step, the weld repair system therefore requires a method to determine if there are defects and which type and size they have. The structures observed by the presented camera system and the measures taken after decision will be discussed exemplarily for two different defects in overlap welding. For the case of a hole, generated by melt ejection, the preferred method to close the hole and keep the connec-tion between the sheets is to weld again with adjusted power. A different treatment is re-quired when there is an undercut, where a defocusing yields best results.

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