| The goal of this work is to better understand micro-scale laser-assisted machining, specifically micro end milling. To do that, a steady-state, two-dimensional analytical heat transfer model of the workpiece, chip, and tool has been extended to the microscale and applied to laser-assisted machining. It is shown that a greater fraction of the generated heat flows into the tool for laser assisted micro end milling of 1018 steel, as compared with unassisted micro end milling. However, the magnitude of heat transfer into the tool is similar in both scenarios, therefore, proving that tool life can increase for laser-assisted machining because the hardness of the workpiece is reduced by a greater extent than the tool. The fraction of generated heat that is transferred into the chip is correlated with the Peclet number of the chip, physically representing the reason that significantly less heat flows into the chip (versus the workpiece) for micro machining as compared with macro- scale machining. The effect of laser preheating on the micro end milling of a fully-dense structural ceramic, silicon nitride is examined with specially designed 2-mm-diameter, two-flute polycrystalline cubic boron nitride tipped end mills. The feasibility of cutting (not grinding) structural ceramics on a small scale is empirically demonstrated and the mechanisms of material softening at high temperatures are reviewed. The generated surface roughness and tool wear are comparable with macro scale laser-assisted machining and macro scale grinding. |
