Surface quality characterisation of diamond cut V-groove structures made of rapidly solidified aluminium RSA-905

V-groove structure is the key composing feature of many optical products such as gratings and optical fibre connectors. The quality of the V-groove structure depends on multiple factors of manufacturing routines, process parameters, material properties, etc. among which the machinability of the workpiece materials plays a crucial role in achieving high-quality V-grooves. Due to the superior mechanical and material properties, rapidly solidified aluminium RSA-905 emerges as an ideal alternative for stainless steel and conventional aluminium alloys for optical components. This paper presents a theoretical and experimental investigation on ultra-precision machining of V-groove structures on RSA-905 using single crystal diamond tools, aiming to reveal some new insights into the material removal mechanism of V-grooving process. A model was established to explain chip flow and material removal phenomena, and effects of depth of cut and feed rate on cutting forces, surface quality and form accuracy were quantitatively evaluated. The results showed that less than 1 pm peak-to-valley (PV) form accuracy and 15 nm Ra surface roughness were obtained on V-groove surface under the best machining condition. A high-stress concentration existed in the vicinity of the straight cutting edges along the slope of the V-grooves, resulting in surface and subsurface damages due to the loss of harder particles. Besides, the unremarkable tool wear and smooth chip morphology demonstrated the good machinability of RSA-905.