Development of Evaluation Model in Three-dimensional Hole Shape made by Rotary Ultrasonic Machining and Elucidation of the Machining Mechanism Based on Designed Experiment

Abstract

This paper describes the evaluation of the inner shape of three-dimensional small glass holes and elucidation of the machining mechanism using statistical analysis based on designed experiment. The glass hole made by rotary ultrasonic machining had a 1mm diameter, and 4 characteristics to evaluate which were expansion of hole size, inner surface roughness, distortion, and direction of distortion. We assumed an elliptical cross-sectional hole shape and distortion, stipulating that an elliptical shape was a more accurate index than a true circle shape to evaluate hole shape and research machining mechanism. Furthermore the replica method used was both accurate and cost efficient enough to evaluate those characteristics. First we did a “Cross Array” experiment to construct models of each characteristic. In this designed experiment, tool factor and mode factor were set in outer array to identify any high order interaction with the machining factors set in inner array. Next we analyzed the correlation of those characteristics and executed analysis of variance. Finally we evaluated hole shape, discussed the machining mechanism and recognized the importance of main effect of the tool and its interactions with feed speed and feed mode. In conclusion, our approach to evaluating three-dimensional hole shape are useful.