Methods for automatic inspection of weld geometry

University essay from Högskolan Väst/Institutionen för ingenjörsvetenskap

Author: Inger Eriksson; [2008]

Keywords: Digital bildbehandling;

Abstract:

The earlier in the production chain discontinuities in the weld area are discovered the better and less expensive it is to modify the weld. If the weld is bigger than necessary the cost and the weight grow, and if the weld is undersized the strength is put at risk. This report contains a summary of a literature survey for finding means for optical measurements of weld geometry. Some of the articles are about existing devices that can measure welds. One is hand-held and is applied on the weld afterwards and compares the data with pre set parameters. Experiments were performed with two different systems to evaluate their capability to capture the weld geometry. The first system is an in - house built system with a laser line diode and a CMOS - camera, the other system is scanCONTROL, and is a device with integrated camera and laser line. Matlab was used to process and analyse data from both systems. Experiments with the first system ended when it was quite obvious that it did not meet the expected result. The laser line projection was too short to cover enough of the weld area and it was hard to process the image to find defects in the weld area. The data from the scanCONTROL system was ready to use and it was quite easy to find different defects and discontinuities in the weld area. It is possible to find the geometry of the weld and it is possible to find defects like spatter, undercut and sharp edges, with laser line projection and camera. The equipment is important in order to extract data useful for analysis.

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