Monitoring laser-welded or -soldered seam for quality, welds series of points and takes images to assess heat dissipation from each

摘要

A series of points is welded. The location of laser welding is moved-on and a camera images each welded point in the seam, before welding the next point. Whilst each image is being taken, the laser is switched off. Alternatively it is in a state of readiness, operating at a minimal power level which does not interfere with imaging. The image is taken after the melt resulting from welding or soldering has at least partially set. The image is taken after a weld has been finished, during an at least partially de-focused traverse over the seam, in a direction opposite to that of welding. The speed of this traverse is at least double that of welding. The image is taken within 0.1-200 ms after switching the laser off, or switching into the readiness state. At least two images are taken after welding, to ascertain the rate of heat dissipation. A mean value is determined from the two images. An evaluation image is generated from them. In each of the two images the lightest or darkest value is selected from each pixel for inclusion in the evaluation image. The camera includes an auto-focusing facility. The laser head (1, 1') used for soldering or welding is implemented as a 3-dimensional scanner. The camera is focused as a function of the varying working state, through Z axis movement of the 3 dimensional scanner. At least part of the laser optical system (2, 2') is used in the beam path of the camera. Optics in this beam path, are implemented such that the welded- or soldered point can be recorded after each repositioning step. After switching to the off- or readiness state, the head moves the processing point such that the position of the seam in the camera image, remains constant for the duration of imaging, even though the head moves relative to the component. Low heat dissipation from the welded point of the component (3) is taken as an indication of defective bonding or strength. Low thermal radiation indicates a defective point in the connecting seam (4). The camera is of the: CCD-, CMOS-, indium gallium arsenide- or thermographic type. It detects light from the visible to the infra-red. The detection waveband is 700-2000 nm. The laser wavelength is filtered-out from the beam path of the camera using a blocking filter. Any smoke, residues or vapor are blasted away by gas flow. To evaluate the image, a software mask is employed. From the quality determined, points of the seam are after-worked, using the laser. An independent claim IS INCLUDED FOR corresponding laser welding and -imaging equipment.