Investigation and analysis on pulsed Nd:YAG laser micro-turning process of aluminium oxide (AlO) ceramic at various laser defocusing conditions.

Laser micro-turning process is one of the latest promising laser material processing techniques which can be employed for generation of micro-turning surface of particular surface profile and dimensional accuracy on cylindrical workpiece. The present paper addresses the laser micro-turning process of cylindrical shaped 99 % pure aluminium oxide (AlO) ceramics of size 10 mm in diameter and 40 mm in length. The experiments have been conducted using response surface methodology design of experiments. The targeted depth was set at 100 μm. Laser average power, pulse frequency, workpiece rotating speed, air pressure and Y feed rate were considered as process variables. After each experiment, surface roughness (Ra) and micro-turning depth deviation have been measured. Empirical models of the responses have been developed based on the test results achieved during measurements of surface roughness and machined depth deviation. Analysis of variance was conducted. Multi-objective optimal parametric combination of process variables has been obtained for achieving least values of responses, i.e. surface roughness and depth deviation. To achieve further high-quality machined surface, machining was done at various defocusing conditions of laser beam and also by varying the number of laser scan passes. Other process parameters were kept constant at optimal parametric combination obtained in multi-objective optimization. From the experimental results, it was revealed that surface roughness decreases with increase in defocusing positions. With increase in number of passes up to a certain limit, surface roughness decreases. However, depth deviation increases with number of laser scan passes at all levels of defocus planes. [ABSTRACT FROM AUTHOR]