Laser-assisted mechanical micromachining

This study focused on numerical modeling and experimental evaluation of laser assisted micro-milling (LAMM). An experimental setup consisting of a 25 W CO2 laser, three CNC linear stages, and a high speed spindle was used to implement the LAMM process. Micro-endmills between 100 and 300 µm in diameter were used to perform slotting and side-cutting operations with and without laser preheat on four materials: AISI 316, AISI 422, Ti-6Al-4V, and Inconel 718. Experimental procedures were first studied and best practices were established including: acoustic emission based methods for tool-workpiece contact detection, laser-tool alignment strategies, assist gas chip removal, and appropriate ranges of machining parameters. Finite volume based modeling of the 3-D laser heating process was performed in order to determine the effect of laser operating parameters on the material removal temperature, peak temperature, and variation in temperature across the material removal area. A novel thermal paint based method was used to determine the absorptivity of each surface and validate the thermal model. A 2-D finite element model of the chip formation process was developed. Material plasticity was considered using Johnson-Cook constitutive models. The FE model incorporated an arbitrary Lagrangian Eulerian adaptive mesh scheme, heat generated by plastic deformation, and the edge radius of the cutting tool. Variations in material removal temperatures, cutting speed, uncut chip thickness, and cutting edge radius were analyzed on the bases of peak tool temperatures and cutting forces. Slotting and side-cutting LAMM experiments were performed based on the results of the numerical models. LAMM results were compared to conventional (no-laser) on the bases of: surface roughness, edge burrs, tool wear, tool life, acoustic emissions, and the microstructure of remaining work material. Significant improvements in all quantitative and qualitative measures were found with LAMM. Neither degradation nor significant change in the remaining workpiece microstructure was observed during multi-pass LAMM at material removal temperatures up to 450 °C. Process improvements with LAMM were heavily dependent on the work material, machining configuration, and operating parameters. LAMM was found to be beneficial for all of the materials in the study during one or more machining configurations