Sensitive drive enables new approach to laser welding
Mechanical scanning instead of camera
Joining thin sheets is the domain of the laser. Whether soldering or welding, the seams are always extremely narrow, accurate and durable. The high energy applied at specific points allows impressive welding speeds. However, this performance requires high-precision control and positioning of the laser. A new method involving mechanical scanning enables optimum positioning and rapid set-up.
Up to now, a camera has been used to record the course of the joint during laser welding. The computer then analyses the image and gives control commands to the welding robot, which then positions the laser head. The disadvantage of this solution is the delayed indirect movement of the head, which always "lags" behind the camera. For reliable optical "seam finding", surface, reflection and illumination must also remain as constant as possible. Deviations result in errors. Therefore the source of these errors has to be eliminated by performing painstaking adjustments. Committed to improving processes within this area, scansonic has chosen a pioneering approach: mechanical scanning.
Mechanically scanned The developers broke new ground with the mechanical laser head guidance, utilizing the essential prerequisites for joining. A shoulder always results at the joint of two sheets – the same applies to angle welding. This is either due to overlapping of the sheets or due to the joint gap. Today, filler material is often introduced to the welding focal point by means of a feed wire. A "scanning wire" is used for this purpose. If these two components are combined, an optimal, i.e. point-accurate, control of the welding head can be achieved.
If the filler wire is continuously pressed lightly against the edge of the overlapping sheet and this force is used as a parameter for the head control, the welding focal point follows the joint course with maximum accuracy. This occurs simultaneously with the movement of the head; delayed control of the head is not necessary. Deviations due to tolerances are compensated for immediately by such a procedure. The seam is thus always applied exactly at the point where it is required – at the edge of the overlap between the joint parts. As this scanning functions purely mechanically, neither optical reflection nor illumination or different sheet surfaces make any difference to the overall performance. Not even shadows or light flashes from other work processes will have an adverse effect. Because the filler wire, as a "lost sensor", is always renewed, there is also no wear.
Pre-fabricated parts can also be securely joined. Tolerances are detected and equalised by the welding head.
Use in the automotive industry
Focal point of optics and filler wire feed meet in the welding point. The telescopic spring with path sensor is responsible for tracking in the z-axis.
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Application Note: Laser Welding
