Einflüsse von Werkzeugdurchmesser und Schneidkantenverrundung beim Bohren mit Wendelbohrern in Stahl
Drilling with twist drills is an often used manufacturing method for the production of drillings, for which a result transmission of conventional tool diameters (e.g. D = 10 mm) to microdrills (D < 2 mm) has not yet been possible. Reasons for this are to be seen on the one hand in the macro and micro geometry of the tools, which for technical reasons can not be transfered linearly from the conventional diameter range to the range of microdrills. On the other hand process variables may affect the drilling process such as the cutting temperatures at the major cutting edges, these temperatures not having been quantified for a tool diameter variation of the conventional range to the range of microdrills. Employment of FEM simulation has proved not to be an adequate means for extending process understanding nor for reducing development and process design costs, since no verified three-dimensional drilling model has been available yet. This treatise essentially deals with three core topics. To begin with, there is the first determination of the cutting temperatures at the major cutting edges of the drills in a diameter range from 1 to 10 mm with the help of the two color pyrometry and the effect of these temperatures on the cutting process. Secondly the application of the "drag grinding process” is proven for the production of defined and reproducible edge roundnesses with radii of 4 µm < = rn < = 40 µm on drilling tools. The effects of an edge roundness of microdrills on tool life and construction unit behavior are examined in detail on macro- and microscopic level and the advantages of the tools rounded by drag grinding are pointed out. On basis of the in step one and two employed tools, the third step develops, optimises and verifies three-dimensional drilling simulations. Here 3D-simulations compare different element numbers and sizes of the workpieces, constant simulation parameters being provided – and pointed out deviations with the feeding force and with the torque. Further numeric investigations examined the influence of the chisel edge and major cutting edge geometry of the tools on the computed feeding force and torque processes as well as on the cutting temperatures. It is shown that the close-to-reality illustration of the cuts forms a substantial condition for a close-to-reality process of strength and moment regarding edge roundness. The employment of ideally sharp tools in the drilling simulation leads to substantial falsifications of the processes, while the verified model shows agreements with experimental results of over 90%.
info:eu-repo/classification/ddc/620, Ingenieurwissenschaften, Bohrer, Bohrwerkzeug, Bohren, Simulation, Temperaturmessung, Pyrometer, 3D-Simulation, Kienzle, Kantenverrundung, Schleppschleifen
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