Steigerung der Leistungsfähigkeit von Vollhartmetallwendelbohrern durch Strahlspanen

(Increasing the Performance of Cemented-Carbide Twist Drills by Abrasive Water-Jet Blasting)

Terwey, I.

To increase the economic efficiency of cutting tools, detailed knowledge of the mechanisms occurring during the machining process is of particular importance. Thus, the influence of each tool-manufacturing step on the cutting process is significant. The reliability can be improved by preparing the cutting edge of cemented-carbide tools before and after the coating process to adapt the cutting edge shape to the process conditions. The main functions of cutting edge preparation are the reduction of cutting edge chipping and the creation of a defined rounding of the cutting edge to increase the cutting edge stability and the wear resistance.

The research activities described in this thesis focus on the performance increase of PVD-coated cemented-carbide twist drills by adapting the cutting edge shape to the machining process of heat-treated steel C45E, based on experimental analysis. The aim is to enhance the process understanding of the cutting edge preparation of cemented-carbide tools as well as the knowledge of the influence of the cutting edge shape on the cutting process. The demand for an improved cutting edge stability is taken into account by application of the abrasive water-jet blasting process for the generation of a defined cutting edge rounding. The influence of the abrasive blasting process on the tool characteristics is analyzed by varying of the process strategy and the process parameters.

The determination of the interaction mechanisms between the process input parameters, the thermomechanical tool loads, and the chip formation process requires a detailed analysis of the complex drill process. In addition to the tool- and workpiece-sided measurement of the machining forces and temperatures, the chip formation is analyzed by metallographic preparation of the generated chip roots as well as of the workpiece surface. Furthermore, the wear resistance of the cemented-carbide twist drills with different cutting edge shapes is determined by drilling tests. Based on the established relationships, a process-specific cutting edge shape for drilling C45E material is designed, taking into account the cutting data and the tool characteristics. Thus, the systematic modification of the cutting edge shape before and after the coating process allows the performance of cemented-carbide twist drills to be improved.

Published as

Dissertation, TechnischeUniversität Dortmund, Vulkan Verlag, Essen, 2011, ISBN 978-3-8027-8766-9