Laser-assisted micro-grinding of Si3N4

Abstract

One of the main challenges in micro-machining of hard to cut materials is the accuracy of the machined part because of high grinding forces which cause tool deflection and rapid tool wear. Non-conventional machining processes have been developed as alternatives to conventional processes for optimizing the machining efficiency and achieving the desired tolerances. This paper addresses a novel Laser-Assisted Micro-Grinding (LAMG) process. For the first time, an ultra-short pulse laser is used to structure micro-grinding tools and a Si3N4 workpiece prior to the micro-grinding. The induced grinding forces and achieved surface roughness as well as the tool deflection and wear by the LAMG process are compared to the Conventional Micro-Grinding (CMG) process. Additionally, the ultra-short pulsed laser ablation process was simulated to find the proper laser parameters corresponding to the desired structure and laser-cut depth. The results proved an enhanced performance of LAMG process in micro-grinding of Si3N4. Using the simulation, the depth of laser cut prior to structuring could be predicted. Structuring, either the workpiece or the tool, significantly reduced the grinding forces. However, a rougher surface resulted via tool structuring. The grinding forces reduced up to almost 40% using 30% structured workpiece surfaces. Structuring the micro-tool (10% structuring) resulted in 60% reduction in the grinding forces with around 40% rougher surface. The accuracy of the part was highly improved by the laser structuring. The actual depth of cut using CMG was 30% lower than the nominal depth of cut. Utilizing LAMG the total nominal depth of cut was removed from material. The comparison between the topography of structured and non-structured tools indicated higher tool wear and shorter tool life with the non-structured tool.