Geometry features of breakage section and variation of cutting force for end mills after brittle breakage

Abstract

Some broken end mills with many brittle breakage sections were collected, and the geometry features of these sections were summed up. As for minor breakage, the breakage sections were narrow planes parallel to the tool edge, and the depths of breakage were shallow. As for severe breakage, it likely occurred near the edge tip; its breakage sections were approximate planes perpendicular to the bottom of tool and tilted approximately 35°to the bottom edge; moreover, the broken degree of section side near the rake face was heavier, while that near the flank face was slighter. By taking these geometry features into account, mathematical instantaneous expressions of cutting force for broken end mills were amended correspondingly. Then, with these expressions, it could be analyzed that, on one hand, the amount of material removed by broken edge segment declined and, on the other hand, its coefficient of cutting force rose; therefore, the instantaneous cutting force might be in reverse relation with broken degree, and in positive relation with feed, and also the removed material by the tooth following the broken one would rise. These results indicate that, if a tooth is brittle broken, there exist two kinds of possibility as rise and decline for its cutting force-the cutting force of slightly broken tooth would rise, while that of heavily broken tooth would decline, the cutting force of tooth following the broken one would always rise, and that of other teeth would remain the same. Using artificial tooth breakage, cutting tests of broken end mills were taken; the test results agreed with above conclusions. Conclusions of this study may be used in modifying indices of monitoring brittle breakage for end mills.

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“…In coincidence with the tool chipping event, a peak in the resultant force and vibration signals were observed, as shown in Figure 6 (a) and (b). the sensitivity of the cutting forces to the breakage event is due to their sensitivity to tool geometry changes [24]. While the high vibrations generated due to the tool chipping caused an instant high burst in the acquired vibration signals, regardless of the vibrations coming from the tool/workpiece engagements.…”

Intelligent Cyber-Physical Monitoring and Control of I4.0 Machining Systems - An Overview and Future Perspectives

“…Different indirect measurements have been utilized and reported in the open literature and correlated to the cutting tool state in machining applications. Cutting forces are considered as the best variable to describe the cutting process due to the completeness of the process information and the sensitivity of the cutting force to tool geometry changes [3,7,8]. However, such a measurement is difficult to make during cutting in real industrial environment.…”