An Experimental study into the size effect in micromilling process

Micro end-milling is one of the main manufacturing processes of creating miniaturized parts which are increasingly demanded in many industries. Using tools with diameter less than 1 mm results in rising the so-called “size effect” and problems due to ploughing at low feeds per tooth. It is therefore crucial to estimate value of minimum chip thickness which helps to reduce or eliminate the ploughing. In this study role of scaling down is investigated with regard to milling operation in micro- and macro-scale. A titanium alloy Ti-6Al-4V is used as workpiece. Two-flute endmills with diameters of 0.8 and 2 mm are used representing micro and macro-scale, respectively. Effects of axial depth of cut and feed rate as input parameters were evaluated on such output characteristics as specific cutting energy, microhardness, surface roughness, topography and chip formation. Results show higher values of microhardness and specific cutting energy in micro-scale. Microhardness and specific cutting energy in micro-scale were found to be 6 times and 150% greater than the macro-scale, respectively. The study suggests that minimum chip thickness can be varied approximately between 0.25 and 0.49 of the cutting edge radius.