R. Villagomez*(a), R. Valenzuela(b), R. Camacho-Mesa(b)
In this work, we present an experimental investigation for welding Nylon: Bi-Oriented Polyamide (BOPA) thin films using a CO2 waveguide laser in a pulsed configuration. The material used in this study is Nylon 6, all set in square sheet thin films samples of 100 cm2 with 15 µm thickness. Our optical setup is based on deliver the laser beam all the way through the work piece using X-Y scanning mirrors mounted on galvo-like motors and an f-theta lens with 15 cm focal length and 50 µm focal spot sizes. The fluence (laser energy) is controlled by a pulse signal generator having the possibility to change the pulse repetition rate (PRR) and the pulse width (PW) of the laser beam. Our results show the best weld seam for scanning speeds of 20mm/s and the pulsed laser beam with 2 KHz PRR and 80 µs for the PW time. The scanning speed and trajectory for the welding process are all controlled by a computer in which one can modify the weld parameters. The irradiance at the focal point is set to 1.146 MW/cm2 while the average optical power was set to 22.5W. Our experimental parameters are previously modeled by using COMSOL Multiphysics software were the laser heat source is modeled on the selected material. This model is based on the heat transfer partial differential equation and solved by finite elements procedure. Model results show a perfect agreement with the experiments. Finally, the quality of the welded seam is studied by means of sealed tight and share force critical mechanical test.
a)Centro de Investigación Científica y de Educación Superior en Ensenada Baja California, Unidad Monterrey, PIIT Monterrey, N.L. 66629 México;
b)Poliflex, S.A. de C.V. Álamo Industrial, Tlaquepaque Jalisco 44490, México.
Form our model results we know the optical and mechanical parameters to start using in our experimental procedure. We perform several welds varying the optical power from 1 W to 25 W and the scanning laser beam speed from 20mm/s to 100 mm/s. Results and measurements are described next. Nylon samples were, then, prepared in rectangles of 10cm by 10cm and put in the work piece stage below the optical scanning setup. The best results ought to be consistent with the previous model results, therefore, we configure our CO2 waveguide laser to deliver 22.5 W at the output and the beam crosses an x-y galvo-like set of scanning mirrors to be focused on the work piece by an f-theta IR lens of 15 cm focal length (see Fig. 1). Figure 7 depicts an image for a cut-and-weld sample using the experimental parameters described above. One can see the seam on a two pieces of nylon for which it is measured its line of stitching width. This corresponds to a 100 µm seam measured with a standard optical microscope with magnification set to 20X and a calibrated reticule. The arrows indicate the left hand seam measured. The inset in Fig. 7 resembles a close-up of a section to be measured.
The authors acknowledge the support received by Poliflex, S.A. de C.V.