Mechanisms of chip formation and cutting dynamics in the micro-scale milling process

Micro-scale milling is an essential fabrication method for miniaturized structures. However, little research has been conducted to gain a fundamental understanding of the mechanisms of the micro-milling process. This study discusses the fundamental mechanisms of chip formation and cutting dynamics in micro-scale milling with a focus on the effects of the edge roundness of micro-tools.; There are three main research topics in this study: The first topic is the development of an enhanced static model of chip formation during the micro-milling processes that is able to describe the intermittency of the chip formation observed at low feeds per tooth due to the dominance of the minimum chip thickness effect. Experimental analyses demonstrate the validity of the proposed model by verifying the periodicity in the cutting forces present at various feeds per tooth. Secondly, the influences of edge roundness on machining stability in micro-milling are discussed. Time-domain simulation techniques are utilized to analyze the interference between forced vibration, which is caused by edge roundness, and regenerative chatter during micro-milling. The variation in machining stability with respect to feed per tooth observed in simulation has been experimentally validated. Finally, the plastic material flow at the tool-workpiece interface in orthogonal cutting with a round edge tool is investigated using molecular dynamics simulation in order to gain a fundamental understanding of round edge effects.; We find that during micro-scale milling, chip formation can be intermittent especially when the feed per tooth is smaller than the minimum chip thickness. Consequently cutting forces may periodically fluctuate with the number of tooth passes. Additionally, there is a local maximum in the relationship between the thrust force and the uncut chip thickness, which may cause significant force vibration of the micro-tool near its resonant frequency. Due to the interference between the forced vibration and regenerative chatter vibration, the variation of the stability limit with respect to the feed per tooth becomes more complicated in micro-scale milling than in conventional scale milling. The information gained in this study contributes to a comprehensive understanding of the micro-milling process that will allow engineers to develop improved tools and processes.