In-Line Monitoring of Interrupted Cutting Operations

Abstract

Intelligent cutting operations capable to adjust in-line their process parameters in order to accommodate unexpected changes of working conditions are more and more desirable in order to increase the current automation level. In order to do that, a general model of the cutting process under investigation needs to be set up in advance, and then, during cutting, continuously compared with the output of process sensor signals. Among the different phenomena that contribute to the general cutting model, the evaluation of the tool wear is a matter of primary importance. The in-line prediction of tool wear critical levels would indeed prevent the production of components of unacceptable quality. The paper presents the development of a tool condition monitoring system and its preliminary results applied to interrupted cutting operations. In the paper first part, the process sensors implemented in the system for in-line acquisitions are described and their distinctive but complementary function in the system evidenced. Later on, the FE-based numerical model of the reference process is presented together with the approach followed for its calibration. It is shown that the numerical model is well suited to reproduce process mechanics, giving chance to understand how wear advancement affects process parameters and component quality. This knowledge can be exploited in building up a general model for wear evolution. Finally, data acquired by process sensors are further elaborated into process control charts that can help in monitoring the tool state as its wear evolves during cutting.

In-line monitoring of cut surfaces in interrupted machining operations

“…Since the monitoring system has to be as quality oriented as possible, the presence of burrs on cut surface was assumed as wear indicator, and an automatic image analysis system was adopted as burr measurement system. Previous work [9] showed that tool wear in circular blades comes in two variants. The first type of wear is repentine and is due to the fragile breakage of one or more teeth, usually causing an abrupt increase in absorbed torque at tool spindle.…”