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Application of Ray Tracing for Interpreting Beam Prints from the Fibre Laser Cutting of Stainless Steel
M. Alotaibi, H. Atiyah, R.C.I. MacKenzie and K.T. Voisey

Two-dimensional (2-D) ray tracing has been used to investigate the influence of inclined cutting front and the cutting edge on the exiting, surplus, laser beam while cutting 6 mm thick stainless steel sheet with a 1070 nm wavelength fibre laser. The ray tracing model, which assumed a Gaussian beam, has investigated the distribution of this surplus beam as a function of kerf wall inclination angle. Multiple reflections are shown to broaden the spatial distribution of the surplus beam. Dross and kerf wall roughness also broaden the spatial distribution of the surplus beam. Comparison of an experimentally obtained beam print from the surplus beam for 1070 nm fibre laser cutting of 6 mm thick stainless steel with modelled results allows inclination of the cut front to be estimated. The experimentally obtained beam print has features consistent with roughness/dross induced beam broadening.

Keywords: Fibre laser, 304L stainless steel, black poly(methyl methacrylate) (PMMA), laser cutting, beam print, surplus energy, ray tracing, two-dimensional (2-D) ray tracing, simulation

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