LASER ABLATION & LASER SPECTROSCOPY
In practice, the precision of the LIBS analysis is strongly dependent on the surface of the material. Real scrap and metal parts often have coatings and riser layers or strong oxidations and other contaminations. These are caused by the production process and use and usually prevent the applicability of the LIBS method. In order to achieve qualitatively reliable measurement results, it is therefore often necessary to thoroughly clean the surfaces or even partially decoat them. In this way the alloy components can be determined "inside" the material. Until now, this decoating was only possible mechanically and not automatically and led to relatively long measuring times, which were usually performed sequentially or even manually.
LASER-INDUCED BREAKDOWN SPECTROSCOPY (LIBS)
With the help of laser-induced breakdown spectroscopy (LIBS), the characteristic fingerprint of the material can be determined quickly and reliably. A high-intensity laser beam is focused on the surface and vaporizes a small amount of the metal close to the surface. During the vaporization process, a plasma light is created, whose characteristic spectrum signals the concentration distribution of the alloying constituents.
At a conveyor belt speed of 3 m/sec, up to 12 ablation passes can be performed in succession. For aluminum the ablation depth is approx. 70 µm per pass, for which the clean2sort module needs less than 4.5 ms. This performance enables us to analyze even heavily soiled, coated and painted materials.
By evaluating this spectrum it is possible to identify the exact alloy of a metal. Thus it is not only possible to differentiate between different metals such as steel or copper, but also within alloy classes. Aluminium of the 5000 alloy group and aluminium of the 6000 alloy groups can be distinguished precisely and unambiguously. Even the differentiation between a 6010 aluminium alloy from a 6016 alloy is in principle possible with the LIBS method.