Markus Beck

Welding of aluminum: A challenging opportunity for laser technology

The increasing demand for lightweight structures has led to a greater industrial use of aluminum alloys. The application of these materials is handicapped by a lack of productivity and reliability in the joining techniques currently available. The laser welding of aluminum is markedly more difficult than for steel. The difficulties to be solved include the threshold for deep penetration welding, the occurrence of material related defects and seam deficiencies such as cavities and blowholes that discourage production engineers from making greater use of lasers. A theoretical analysis reveals the requirements that have to be fulfilled by laser systems in order to obtain process stability. In comparison to steel greater focusability and shorter wavelengths are needed. An intensity distribution leading to a V‐shaped keyhole is also beneficial. The results of this analysis are confirmed by welding results obtained with CO2 and Nd:YAG lasers. An increase in process stability is observed when a dual beam techniq...

Energy Coupling in Surface Treatment Processes

In cutting or welding processes with lasers, deep penetration mechanisms allow high energy coupling rates. In surface treatment processes such as martensitic hardening, cladding and alloying, deep penetration of the laser beam is mostly not applicable. This generally leads to insufficient coupling rates. In this contribution several ways of enhancing the coupling rate are summarized. Following some theoretical considerations, results of experimental verifications are given.

Welding of aluminum: Challenge and chance for laser technology

Increasing demand for light-weight structures leads to enlarged use of aluminum alloys. The application of these materials is handicapped by a lack of productivity and reliability of available joining techniques, however. Laser welding of aluminum, on the other hand, turned out to be markedly more difficult than the treatment of steel. Difficulties to overcome threshold for deep penetration welding, the occurence of material related defects and seam deficiencies such as cacities and blow holes discourage production engineers from making use of lasers.A theoretical analysis reveals requirements that have to be fulfilled by laser systems in order to obtain process stability. In comparison to steel better focussability and shorter wave-lengths are needed. An intensity distribution leading to a v-shaped key hole is beneficial, too. The results of this analysis are confirmed by welding results obtained with CO2 and Nd:YAG-Iasers. An increase in process stability is observed when dual beam technique or the shorter wave length laser is applied. In conclusion, welding of aluminum alloys with appropriate laser systems proved to be ready for industrial application, now.Increasing demand for light-weight structures leads to enlarged use of aluminum alloys. The application of these materials is handicapped by a lack of productivity and reliability of available joining techniques, however. Laser welding of aluminum, on the other hand, turned out to be markedly more difficult than the treatment of steel. Difficulties to overcome threshold for deep penetration welding, the occurence of material related defects and seam deficiencies such as cacities and blow holes discourage production engineers from making use of lasers.A theoretical analysis reveals requirements that have to be fulfilled by laser systems in order to obtain process stability. In comparison to steel better focussability and shorter wave-lengths are needed. An intensity distribution leading to a v-shaped key hole is beneficial, too. The results of this analysis are confirmed by welding results obtained with CO2 and Nd:YAG-Iasers. An increase in process stability is observed when dual beam technique or the shor...

Characterization of pulsed Nd:YAG-laser beams as an optimization tool in laser drilling applications

The attainable precision and reproducibility in material treatment with pulsed Nd:YAG-lasers strongly depends on the characteristics of the laser beam itself Therefore it is essential for the process and tool optimization to have comprehensive information of the relevant laser beam data. Especially flash-lamp pumped lasers working in pulsed mode often have intense fluctuations in their temporal and spatial radiation characteristics, which are caused by a multitude of transient physical processes.This contribution shows a measuring method and device for an adequate characterization of pulsed laser sources and their beam delivery systems. The technique of spatial beam deflection used herein is able to measure energy density profiles of successive single pulses with repetition frequencies of up to 20 kHz (3 kHz real time). The measuring device can be used for off-line or in-process measurements. Its application for the laser qualification and especially its contribution to the development of a new pulsed drilling laser are demonstrated.The single pulse characterization will be presented as an in-process control tool for pulsed laser applications. Furthermore the correlation between laser beam profiles and hole shapes for the single pulse drilling process is discussed.The attainable precision and reproducibility in material treatment with pulsed Nd:YAG-lasers strongly depends on the characteristics of the laser beam itself Therefore it is essential for the process and tool optimization to have comprehensive information of the relevant laser beam data. Especially flash-lamp pumped lasers working in pulsed mode often have intense fluctuations in their temporal and spatial radiation characteristics, which are caused by a multitude of transient physical processes.This contribution shows a measuring method and device for an adequate characterization of pulsed laser sources and their beam delivery systems. The technique of spatial beam deflection used herein is able to measure energy density profiles of successive single pulses with repetition frequencies of up to 20 kHz (3 kHz real time). The measuring device can be used for off-line or in-process measurements. Its application for the laser qualification and especially its contribution to the development of a new pulsed dri...

High-speed laser beam diagnostics for pulsed lasers

Since pulsed Nd:YAG lasers are used more and more in industrial production, there is a need for the fast and reliable beam characterization of these devices. This is even more important for flash-lamp-pumped laser systems which show strong fluctuations in the energy density distribution of their single pulses resulting in quality or performance variations and poor reproducibility in material processing. Within this paper the requirements for a diagnostic device used for observation and measurement of pulsed laser radiation are defined with respect to the needs of the laser drilling process. This device must be able to observe the shot to shot stability of the main beam parameters. Unfortunately, the most common beam measurement devices are designed mainly for cw-beam diagnostics. For this reason, we have investigated a measurement procedure and developed a prototype for laser beam diagnostics adapted to the needs of laser material processing. The special demands of the process, the measurement principle as well as the prototype and first experimental results will be discussed.