Force Modeling for Laser Assisted Micro-Grooving

Laser Assisted Mechanical Micro-machining (LAMM) is a process that utilizes highly localized thermal softening of the material by continuous wave laser irradiation applied simultaneously and directly in front of a miniature cutting tool in order to produce micron scale three dimensional features in difficult-to-machine materials. This process can produce lower cutting forces and deflections, prevent catastrophic tool failure and potentially increase the material removal rate. The miniature machine-tool system used to implement this process has a finite stiffness and therefore deflects under the cutting forces. The deflections may be of the same order of magnitude as the depth of cut in some cases, thereby having an effect on the dimensional accuracy of the micro-machined feature. As a result, selection of the laser and cutting parameters that will yield the desired reduction in cutting forces and deflection, and consequently an improvement in the dimensional accuracy of the micro-machined feature requires a reliable cutting force model. This paper describes a cutting force model for a laser-assisted mechanical micro-grooving process. The model combines an existing slip-line field based force model with a finite element based thermal model of laser heating and a constitutive model of the material flow stress to predict the cutting and thrust forces. Experiments are carried out on H-13 steel (42 HRC) to validate the force model with and without laser heating. The effects of LAMM parameters such as laser power, cutting speed and laser beam mode — Gaussian versus Uniform — on the forces are also analyzed. The predictions from the force model are within 10–20% of the experimental values with most below 15%.