Fabrication of micro holes using low power fiber laser: surface morphology, modeling and soft-computing based optimization

Fiber laser micromachining is found extensive applications at industrial level because it is cheap and simple to use. Due to its high strength and low conductivity titanium is difficult to machine with conventional methods. In this investigation, micro holes were fabricated using a 30 W fiber laser on 2 mm thick α-titanium (Grade 2) and the process parameters were optimized through response surface methodology (RSM) and teaching learning-based optimization (TLBO) approach. Experimental runs were designed as per rotatable central composite design (RCCD). Material removal rate (MRR), hole circularity (HC), deviation in diameter (DEV) and heat affected zone (HAZ) were selected as output. A third-order polynomial prediction model was established using RSM. Analysis of variance (ANOVA) suggested that the developed model was 93.5% accurate. The impact of input factors on responses were studied by 3D surface plots. RSM desirability indicates that optimum micro drilling conditions are scan speed 275.43 mm/s, frequency 24.61 kHz, power 36.23% and number of passes 49.75. TLBO indicates that optimum micro drilling conditions are scan speed 100 mm/s, frequency 20 kHz, power 20% and number of passes 50. Comparison between RSM and TLBO suggested that TLBO provided better optimization results. Surface morphology of the fabricated micro holes were analyzed with scanning electron microscopy (SEM).