In situ chip formation analyses in micro single-lip and twist deep hole drilling

Kirschner, M.1, a; Michel, S.1, b; Berger, S.1, c; Biermann, D.1, d; Debus, J.2, e; Braukmann, D.2, f; Bayer, M.2, g

Institut für Spanende Fertigung, Technische Universität Dortmund, Baroper Str. 303, 44227 Dortmund
Lehrstuhl Experimentelle Physik 2, Technische Universität Dortmund, Otto-Hahn-Straße 4a, 44227 Dortmund

a); b); c); d); e); f); g)


Growing competitive pressure forces companies to optimise process productivity and shorten primary production times. At the same time, the resulting manufacturing quality must be kept on a high level. In the automotive sector, deep hole drilling with smallest tool diameters is an important process, e.g. to produce lubrication holes in crankshafts and fuel channels in injectors. A crucial criterion for the achievable productivity and manufacturing quality with respect to the dimensional and shape tolerances as well as the surface quality in smallest diameter deep hole drilling is the chip formation. Therefore, in-depth analyses regarding the mechanisms of chip formation at the cutting edge and the chip removal along the chip flutes are indispensable. To accomplish an indepth chip formation analysis in smallest diameter deep hole drilling, a new methodology of analysis has been developed. Samples made of the particular test material are inserted into acrylic glass carriers, and the chip formation in the operating zone and the chip removal are documented by high-speed microscopy. In this paper, the experimental setup of the newly developed methodology of analysis and the experimental results for single-lip and twist deep hole drilling of high-strength bainitic steel with smallest diameters are shown. The investigations show the dependence of chip formation on the changes of the microstructure of the cutting edge due to tool wear, and form the basis for an optimization of the tools. In addition to that, a new approach to visualise machining processes running under non-transparent coolant is presented.


Micro machining, Single-lip deep hole drilling, Twist deep hole drilling, Chip formation


International Journal of Advanced Manufacturing Technology, (2017), doi: