Quality
Quality
Laser beam welding
A quality monitoring and assurance system (statistical process control) is used to ensure maintenance of the high quality requirements for the production of tailored blanks and for production of the primary materials used.
Order-related quality control begins in the steel plant and continues through the subsequent production stages (cold rolling, coating). The organisational procedure is certified in accordance with DIN ISO 9000 ff.
Many years of experience in the preparation of blanks, by now proven a million times over, guarantees optimum precision and reproducibility.
The production of tailored blanks itself calls for fullyautomatic and to some extent newly-developed production processes that ensure economic and safe production. It requires modern techniques for monitoring of the welding process and of product quality. In order to meet the demands of these new fully-automatic production processes for the manufacture of tailored blanks, Thyssen Fügetechnik GmbH, the ThyssenKrupp Stahl research division, Thyssen-Laser-Technik GmbH and Thyssen Nothelfer GmbH addressed the different possibilities of automatic evaluation of weld seam quality and the control of production processes at a very early stage. Even the first welding plant, which began operating in 1985, featured a combination of different sensor systems for evaluation of the joining gap and the welding process. In recent years this technique has been further developed and improved in different stages. It is possible not only to control the welding process itself but to evaluate the weld seam with the latest generation of this technology, which was developed on the basis of existing systems.
Light-section sensor for evaluation of geometry of seam profile
A sensor system (seam observation system) mounted behind the welding head measures the weld seam geometry. This makes it possible to ascertain and document the quality of the seam in conformity with the specification agreed with the customer.
The system as described above is supported by a PMS sensor (plasma monitoring sensor) which observes and evaluates the constancy of the welding process itself.
Plasma sensor for the monitoring of the welding process
Plasma Monitoring Sensor for the evaluation of the welding process
Accordingly the Thyssen LAM (Laser Application Manager) combined weld seam inspection system is capable of detecting not only trend defects such as irregularities in seam geometry (cap incidence, edge displacement, root sag) but small extent defects, such as pores and holes. The combined lightstripe and plasma sensor system has been optimally supplemented, so that the high measurement rate makes it possible to ensure a defect resolution that safely detects the slightest defect even at a high welding speed.
Light-stripe sensor for the detection of the butt joint and the gap width
A computer-assisted evaluation system automaticAally evaluates the sensor signals even during the welding process. This makes it possible to determine whether conditions at the relevant measuring points comply with the specified requirements, or whether deviations leading to a drop in weld seam quality have occurred.
The welded blanks are removed from the conveyor belts or the clamping table by means of removal devices, and are placed in the blank stack in the case of a conforming weld, or automatically extracted if a non-conforming weld is in question.
During the welding process, the temperature of the seam is registered by infrared measurement. Comparison with the set values indicates compliance with the required weld quality
The evaluated sensor data record for each tailored blank is stored in a short protocol. This allows the quality of the product to be documented.
An integrated error detection system warns the operator of any mechanical defects that occur in the fully-automatic welding facility. The quality assurance and monitoring system has been extended for the new plant concept for the production of non-linear laser-beam welds.
A sensor positioned before the welding head is able to detect the joint edges of the sheets that are to be welded. This not only allows the exact position of the joint edge to be ascertained, but allows the gap between the sheets to be measured. The operator is advised as soon as the indicated gap measurement exceeds a predetermined limit value, and the blanks are automatically sorted out. In addition, with this type of plant the joint edge detection signal is also used for exact tracing and adjustment of the laser beam to the joint edge.
Quality assurance equipment at laser conti welder