18 07 19

Pagina 1

Course of ADVANCED MANUFACTURING PROCESSES Proff. Michele Monno – Barbara Previtali – Matteo Strano SURNAME NAME PERSONAL ID Exam – July 18th 2019 Exercise n. 2 – technological problem Your company needs to evaluate the capabilities of laser drilling on pure Copper which is a high reflective material (material properties reported in Table 1). As an application engineer of a laser laboratory you are requested to determine the best process parameters and laser source for the proposed application with the facilities available within the lab. To start, you decide to perform some tests on a Copper metal sheet. The laser drilling is firstly performed in a single step, but in order to obtain ablation the surface has to reach a temperature of 2500°C. The micro holes should be characterized by a diameter of 50 µm. You have at your disposal two options in terms of pulsed laser sources and optical setup. Option 1, involves the use of a pulsed laser emitting at the green wavelength whose specifications are reported in Table 2 (option 1). In order to focus the beam on the surface that has to be processed, you have at your disposal a mirror with a changeable position (from a minimum position x=0 mm up to a maximum position x=130 mm). A schematic representation with the constraints of the optical set-up is reported in figure 1; it is suggest to consider the little divergence of the collimated beam; it is not possible a change of the vertical position. The second option involves the use of a fiber laser and a traditional proximity head. You have at your disposal two possible focusing lenses. It is possible a change of vertical position. The parameters of option 2 are reported in Table 2 (option 2). Assumption: rectangular shape of pulses Table 1 Material properties – Pure Copper…