Investigation of chip formation in high speed end milling

Ball-nose end mill cutters are used extensively in the die and mold industry. However, very little work has been done in the research of chip formation in high speed ball-nose end milling. An experimental investigation has been conducted in this study to establish the chip formation mechanism. Common mold steel H13 hardened to HRc 55 is machined on a high speed machining center under dry conditions at a spindle speed range of 10–30k rpm. Four typical types of chip and three types of chatter have been encountered in this study. Images of the chips are obtained by the use of SEM. The EDX method is used to analyze the interaction between the cutting edge and the chip in the formation process. Based on the findings of this study, the chip formation mechanism has been proposed in this paper. The locus of cutter movement for the three types of chatter is illustrated to explain the relationship between the chip formation and the chatter behavior. A method to judge process stability by analysis of the chip has been suggested based on the findings of the experiment. It has also been established through this study that the classical “adiabatic shear” does not occur in chip formation in high speed ball-nose end milling.