Effect of cutting edge radius on micro end milling: force analysis, surface roughness, and chip formation

Producing miniaturized components from a wide variety of engineering materials is one of the most important fields of interest in manufacturing industry. Micro end milling is considered to be one of the efficient methods to produce complex 3D micro components. In micro machining, undeformed chip thickness is comparable to the tool edge radius, which introduces a critical undeformed chip thickness. Below the regime of critical undeformed chip thickness material is not removed but plowed. Ti-6Al-4V is one of the most popular titanium alloy because of its superior properties such as resistance to heavy loads, corrosion resistance, lightness, and bio-compatibility. This paper investigates micro end milling characteristics of the Ti-6Al-4V titanium alloy through a series of cutting experiments. Here the size effect in micro end milling was observed by studying the effect of the cutting edge radius on process performance. In order to understand the effect of the cutting edge radius on machining performance, range of feed per tooth was selected in such a way that it includes both within and outside the size effect region. This paper explores how cutting edge radius affects the cutting force, coefficient of friction, surface roughness, and chip formation during the micro end milling process. A size effect region was obtained from the variation of cutting force with feed per tooth. It was found that feed per tooth in the vicinity of 1-μm range is critical feed per tooth value, which is approximately one third of the cutting edge radius. Below this value, the cutting edge radius effect is predominant which would result in more ploughing mechanism. This was evident from the deviation of cutting force from the linear trend, increase in coefficient of friction, and surface roughness value at lower feed per tooth. In addition, a cutting force model was proposed considering the cutting edge radius effect and has been validated with experimental results.