Development of universal wireless sensor node for tool condition monitoring in milling

Advanced material processing technologies require non-traditional monitoring system devices to provide real-time information on the ongoing technological processes. The article proposes a sensor node composed from cone-shaped tool holder for shank-type rotating tools with embedded self-powering wireless data processing and transmission system. Design of the tool holder with helical slots on its surface is prepared and presented. These helical slots introduced on the surface of the cone-shaped tool holder transforms the cutting tool torsional (T) vibrations present during operation into the longitudinal (L) vibrations that propagate through the tool holder in the axial direction and excite the piezoelectric transducer. The purpose of the developed sensor node inside the tool holder is to monitor the heavy lubricated milling process which is expressed by the capacitor load rate of harvested electric charge, which depends on the conditions of the cutting tool. The electric charge generated by exciting of piezoelectric transducer from the cutting tool vibrations exponentially rises until the capacitor is fully charged and the capacitor charging time interval is recorded while the harvested energy is used to power auxiliary electronics with wireless data transmission capability. As the intensity of energy accumulation depends on the state of the cutting tool wear, the capacitor charging time is used to detect changes in the tool condition. Such proposed real-time cutting process monitoring allows controlling the quality of the workpiece being machined and preventing damage to the equipment. This paper is dedicated to the research and development into one of the key stages of “Industry 4.0,” using cybernetic-physical components, numerical models, and self-powering wireless monitoring systems for the application in context of the “Internet of Things” (IoT).