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In this work, we present a dynamic extension through the combination of an acousto-optical deflector (AOD) with a galvanometer scanner. This combines the best of two worlds: the dynamic beam deflection of the AOD and the large scanning field of the galvanometer scanner. The integrated AOD is able to deflect the laser beam pulse by pulse within its scanning field and to modulate the beam intensity simultaneously. The mechanical limitations and problems of the galvanometer scanner, such as vibrations and overshoots due to fast mirror rotations, can be specifically compensated by the high precision of the AOD. As a result, in addition to process time reduction, the surface and image quality improves significantly. In any case, the laser source needs synchronization with the AOD because the propagation of sound waves within the AOD crystal is slower than the laser pulse propagation through the medium. In the first step, a comparatively slow AOD based on tellurium dioxide with a transversal crystal alignment is used. The process time of a thin film ablation with 4 μJ at 1 MHz was reduced considerably by applying a USP laser system (Coherent Monaco).
Lately, there has been tremendous progress regarding the developments on vehicle safety. One example is the integration of super high-strength steels and carbon fiber reinforced plastics, concurrently meeting the requirements of weight reduction. As a result, mechanical rescue systems like hydraulic shears reach their performance limits.
The main goal of this work is the development of a mobile laser cutting device for rescue operations. The focus is put on high flexibility concerning the processing of high-strength materials and multilayer structures. Moreover, robustness, easy handling and system weight shall be optimized, as rescuers often work under harsh conditions concerning temperature, humidity, dirt and stress. Crucial aspect of laser rescuing is safety which must be guaranteed for all persons involved at any time. Here, results of laser cutting experiments, using materials and structures relevant for rescue situations, are presented.
In this work, a new near-infrared laser-based process chain is presented to overcome the deficits of conventional brazing-based repair of diamond-tipped steel saw blades. Thus, additional tensioning and straightening steps can be avoided. The process chain starts with thermal debonding of the worn grinding segments, using a continuous-wave laser to heat the segments gently and to exceed the adhesive’s decomposition temperature. Afterwards, short-pulsed laser radiation removes remaining adhesive from the blade in order to achieve clean joining surfaces. The third step is roughening and activation of the joining surfaces, again using short-pulsed laser radiation. Finally, the grinding segments are glued onto the blade with a defined adhesive layer, using continuous-wave laser radiation. Here, the adhesive is heated to its curing temperature by irradiating the respective grinding segment, ensuring minimal thermal influence on the blade.
For demonstration, a prototype unit was constructed to perform the different steps of the process chain on-site at the saw-blade user’s facilities. This unit was used to re-equip a saw blade with a complete set of grinding segments. This saw blade was used successfully to cut different materials, amongst others granite.
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