They design a system for the detection and control of defects in welding laser

The welding laser employs in sectors like the one of the automotion, since it comports diverse advantages, like the automation. Nevertheless, during the process sometimes produce defects, as they are the apparition of holes or the fault of penetration, when the cord of welding does not arrive until the depth wished. The origin of these defects is diverse and can involve, for example, the break of the welding in back processes.

Thus, four SMEs and four centres of investigation of five European countries have carried out a project of the VII Program Mark consistent in the development of a system of detection of defects in real time and of a system of control associated. In the project, designated CLET, participate two Spanish entities Leonese, the technological centre Cartif of Valladolid and the SME burgalesa Josdan Welding Laser and Adjust.

Sergio Greet, researcher of Cartif and scientific coordinator of the project, remembers that the idea arises of another investigation realised in collaboration with Renault. “The study treated to detect defects in welding laser and check that a system like this remained short, since it interested that besides it was able to act on the machine of welding to be able to carry out actions correctivas”. To the not being able to develop this line by the conclusion of the project, decided to request a new study to European level.

Initiated in November of 2008 and concluded recently, the Project CLET has tackled two main challenges. The first centres in the development of a system of detection of defects in real time.

“For this choose a road of study quite new, based in studying the plasma that generates the welding laser in the zone of interaction laser-steel. In this plasma there are free electrons, that is to say, electrons that have freed of the links that tie them to the atoms”, explains Healths, the one who remembers that the energy of these free electrons can measure and designates electronic temperature. The researchers checked in laboratory what already had showed in the literature, that the electronic temperature relates with the apparition of defects in the welding and, analysed one of them, the profundiad of penetration.

The second part of the project consisted in creating a system of control. “The system knows the ideal value of electronic temperature and what does is to calculate the parameters of the laser in real time so that this value measured was always very near of the ideal value”. Like this, the system only acts on the power of welding, changing the power of the laser to regulate the depth of penetration.