| Summary: | This Ph.D. project provides for the first time the basic characteristics of fibre laser interaction with pine wood in dry and wet state. Fibre laser has gained importance in the laser material processing market as it presents an advanced technology. It is compact, reliable and more efficient than CO2 and Nd:YAG lasers. The high quality laser beam generated is currently in the kilowatt power level suitable for cutting operations. Furthermore, this laser system needs low maintenance and it has very long working life. It also presents the flexibility of fibre delivery, up to 200 meters from the laser source. Three major experiments were performed: laser cutting of dry pine wood with multiple passes of the laser beam; the laser cutting of wet and dry pine wood; analysing the effect of single and dual assisting gas jet(s) in the fibre laser cutting process. In each experiment, the main process parameters and their interactions affecting the process were discussed. Furthermore, the application of a desirability equation provided the optimal combination of the parameters involved (within the experimental window tested) to maximise the yield and the quality of the laser cutting operation. The effect of the assistant gas jet(s) was further analysed with a computational fluid dynamic (CFD) model, which information clarified its/their action in ejecting fumes and combusted materials in the process. Finally, an application study of Ytterbium fibre laser cutting of hardwood branches was performed; the results obtained were compared with CO2 laser cutting results reported in the literature.
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