Development of die-embedded micro sensing system for sensing and control system in precise metal forming processes

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A die-embedded sensing system was developed. A prototype of micro sensor chip was fabricated by using photolithography technique. The micro sensor chip with dimensions of 3.4 mm×4.6mm was fabricated. Four sensor units are allocated in the chip with certain distances in circumferential direction, and each sensor unit consists of four strain gauges with dimensions of 0.3mm in length and of 0.1mm in width which are connected as a Whitestone bridge. The sensor chip was embedded near the contact surface with the location at the concentric circle with the contact surface of die. All of the sensor units are connected to a flexible cable, which was extended to out of the die. The sensor chip was completely included in the die, and could be connected to an amplification circuit with antenna so that the user could obtain the information without setting up any additional sensors to the bending machine. As a case study, we applied the die-embedded sensing system to V-bending process. Micro sensor was designed and fabricated for measurement of the load and the bending angle during the processing. The results show that new sensing system has its advantage in comparison with the conventional sensors. The die-embedded sensing system could be a new sensing technique to measure complicated phenomena by monitoring stresses/strains in the die during the process of sheet metal forming.