Burr formation and surface roughness characteristics in micro-milling of microchannels

Microchannels are attractive for their widespread applications in electronics, biological, chemical, and energy areas. Micro-milling provides an ideal method to fabricate microchannels, whereas problematic burr formations and inherent rough surfaces of microchannel bottom and sidewalls are still far from sufficiently known. In this study, micro-milling process of rectangular copper microchannels was conducted by a two-flute tungsten carbide micro-end mill. Burr formation mechanism was studied via 3D finite element simulation together with experiment observations. Surface quality of microchannels, i.e., burr size and surface roughness, was studied in different spindle speeds, feed rates, and depths of cut. It was found that the top burr sizes on the down-milling side of microchannels were much larger than those on the up-milling side. The top burr size on the down-milling side and surface roughness on bottom and both sidewalls of microchannels presented a monotonic decreasing trend when the spindle speed increased, and an increasing trend with increasing depth of cut. Nevertheless, they firstly decreased due to the plowing and extruding effect together with elastic recovery when the feed rate was smaller than the tool cutting edge radius, and then changed to increase due to the shearing and cutting process after the feed rate exceed the tool cutting edge radius. High spindle speed, small depth of cut, and moderate feed rate close to the tool cutting edge radius seem to be favorable to improve surface quality of micro-milled microchannels.