Milling Tool-Workpiece Contact Detection Method Using Electric Conduction

Abstract

The relative motion between the tool and the workpiece is transferred in machining, making the precise identification of their relative positions essential for achieving high-precision machining in addition to ensuring the motion accuracy of the machine tools. This identification process, typically conducted before machining, is crucial for setup. Although several on-machine identification methods for tool-workpiece relative positions have been suggested, they are often either indirect or costly. Consequently, none combine high precision, high efficiency, and automation capabilities. In this study, a method for detecting contact between the tool and the workpiece surface during the milling process is developed, allowing direct identification of the relative positions between the tool and the workpiece used for actual machining. A conduction circuit is installed between the tool and the workpiece, and regression analyses of the conduction signal are performed to identify precise contact positions using a duty-ratio-based model and an integral-value-based model. The effectiveness of the proposed method is evaluated through experiments, demonstrating that the proposed method successfully identifies the relative position between the tool and workpiece with high accuracy, achieving less than 1 μm precision.