Size Effects in Drilling Burr Formation

Despite the existence of numerous competing technologies, drilling is the most common and still highly demanded manufacturing process in production industries. Mostly, the manufacturing of a through bore-hole is attended by the formation of an entrance and an exit burr. Thereby, the dimension of the exit burr exceeds the entrance burr considerably. Due to the hangover on the drill exit surface, the quality of the workpiece is reduced significantly. For this reason, the removal of the burr is often required. But in case of micro-drilling no appropriate tools are available. In addition, the manual removal of the burr, which is often used for conventional drill sizes, is impossible for such small geometries.

An efficient method for solving the burr problem in conventional machining is the reduction of the burr size to a tolerable size level by adapting cutting parameters, tool properties or workpiece properties. Numerous investigations have been presented on this field in the last years, but the reached expertise can’t be transferred to micro-machining. Based on the rising influence of the grain structure in micro-machining, certain size effects occur when scaling the cutting process from the macroscopic to the micro level. As soon as the drill diameter is smaller than 1000 μm the feed per tooth and the cutting tool geometry comes into the order of magnitude of the grain structure. Thus, the characteristic of the workpiece material switches from homogeneous to anisotropic. Since there only exist investigations to a few discrete diameter ranges, the resulting influences on the burr formation are widely unknown. In this paper the size effects of the drilling burr formation are investigated in systematic scaled drilling series over a wide range of drilling diameters (Ø 0.01 mm–14 mm).