Machining, Measurement, and Control Laboratory

High Productive Direct Tapping by Intelligent Machine Tools
Yoshinori Yamaoka (Yamazaki Mazak Corp.)
Yoshiaki Kakino (Kyoto University)

This paper presents methodologies to enhance the productivity and to extend the tool life in direct tapping processes by using the Intelligent Machine Tool. Thrillers-type direct taps, which perform both drilling and contour machining by one tool, require less machining time compared to other types of direct taps. A critical issue is that it is often subject to a large cutting force when the contour machining process starts. The tool breakage is most likely to occur at the beginning of the contour machining process, because the arc length of cutting engagement becomes maximum at this point. To prevent the tool breakage and to enhance that productivity in direct tapping processes, we employ a constant cutting force control method by regulating the feedrate according to the arc length of cutting engagement. Experimental studies are conducted to validate its effectiveness to extend the tool life and shorten the total machining time. Furthermore, a tool life detection method in drilling processes based on the estimated cutting force is also presented.

Keywords:   Intelligent machine tools, direct tapping, tool life, cutting torque, cutting force.