Non-destructive measurement of MUCT in micro-milling using surface topography generated by bi-planer size effects

Abstract

In mechanical micro-cutting, a Minimum Undeformed Chip Thickness (MUCT) is desired to ensure chip formation by the round-edged tool. Although the MUCT controls several machinability, productivity, and sustainability attributes, its measurement using output responses is a challenging task. This article, for the first time, demonstrates a non-destructive methodology to measure MUCT in micro-milling using the topographical pattern that inherently remains embedded on the micro-milled floor surface in the form of a microscopic step at the ploughing-shearing transition boundary. Simultaneous action of two Size Effect phenomena that occur concurrently in two mutually perpendicular planes owing to rounded-nose and rounded-edge produce microscopic step during surface generation. A methodology to quantify MUCT using this inconsistent surface topography is also demonstrated. MUCT remains within 36–41 % of the edge radius during dry micro-milling of Ti-6Al-4V using TiAlN-coated WC-6Co tool. The same reduces to 33–40 % of the edge radius when cutting fluid is delivered through sustainable Minimum Quantity Lubrication (MQL) strategy. Proportionality between MUCT and edge radius remains valid during abrasive wear regime of the cutting tool. Tool wear significantly deteriorates surface quality, causing Ra roughness to increase from 40 to 350 nm when adhesion deposits on cutting edge. Consequently, the proposed surface-dependent methodology fails to provide precise MUCT data when cutting tool experiences aggressive wear.