Noncontact measurements of acoustic emissions from the single-point turning process

Abstract

Single-point turning is a fabrication process that is fundamental to manufacturing, comprising a significant portion of value-added operations. Vibration at the tool/workpiece interface affects surface finish, residual stress, and chemical reactivity of machined components. This phenomenon also affects tool life and therefore production cost. The study and measurement of this phenomenon has traditionally been done using a transducer in contact with the cutting tool or is in line with the cutting tool/tool holder assembly. While this setup has been acceptable for laboratory studies, implementation on actual production platforms has not been widespread, with open loop machine tool parameter control still being the norm. The goal of this study involves the use of a noncontact transducer (microphone) to gauge detectability and measurability of machine tool vibration attributable to the single-point turning process performed on a manual lathe situated in a shop floor environment. Such measures as characterization of the frequency content transmitted and the sound pressure level measured while machining a group of materials of interest are quantified and discussed. The results of the work show that the acoustic energy attributable to single-point turning is detectable using the noncontacting sensor, producing energy mostly in the ultrasonic (f > 20 kHz) range. Individual materials of interest (M42 tool steel, tungsten tantalum alloy, aluminum 6061, and Nitronic 33 stainless steel) are shown to emit distinct frequency signatures when excited using identical process parameters. Potential sources of ultrasonic acoustic emission are postulated and discussed, along with control of the turning process using the acoustic signal as an input and selected process parameter changes as the output.