Kovvuri, Vivekananda Reddy (2015-08). Experimental Study of Built-up-edge Formation in Micro Milling. Master's Thesis.
Micromachining relies on precise tool geometry for effective material removal and acceptable surface finish. The detrimental built-up-edges (BUEs) not only degrade the surface finish of machined features, but also pose a concern for critical applications when BUE can be eventually detached from machined surface. This work presents experimental study on conditions for BUE formation and its effects in micro milling of biocompatible 316L stainless steel. Surface finish and BUE density on a micro milled surface are used to quantify the presence of BUE. A new micro tool is used for each milling condition. A BUE, embedded onto a milled surface, is identified by scanning electron microscopy and energy dispersive X-ray analysis. Optical microscopy is used to quantify BUE density at different locations and milling parameters. Surface finish data from meso-scale milling agree with predicted surface finish, but the model fails to predict the surface finish in micro-scale milling. Micro milling resulted in rough surface finish at low cutting speeds and chip loads due to formation and detachment of BUE from tool surface to machined surface. Hence a new surface finish model including the effect of BUE and tool wear was developed.