Machining optimization in rotary ultrasonic drilling of BK-7 through response surface methodology using desirability approach

Abstract

In the present work, optical glass BK-7 was drilled by rotary ultrasonic machine. Response surface methodology was amalgamated with desirability approach to frame the experimental matrix and seek pragmatic solutions to cope with the real machining problems. Spindle speed, ultrasonic power and feed rate were extensively scrutinized to evaluate the machining proficiency in terms of material removal rate (MRR) and surface roughness (SR). Thereafter, ANOVA check was exercised to scrutinize the adequacy of developed SR and MRR models and cast light on the significant model terms with their impact intensity on responses. The feed rate was observed to be the most influential factor in determining the qualitative (SR) and quantitative (MRR) aspect of the machining process. The machined surface along with tool surface was examined by scanning electron microscope to shed light on the material fractography and tool wear. Processed surface topography revealed the concluding evidence of brittle fracture dominance along with few traces of plastic flow of material. Severe tool wear was observed in the initial stage of experimentation due to bond fracture and grain fracture. Confirmatory tests validated the prediction accuracy of developed models by keeping the error within 5% between the predicted and experimental value at 95% confidence level.