Automatic Control System for Mass Production Using Press Forming

In various manufacturing processes, feedback control systems have been investigated to enhance productivity. However, applications in practical mass production are still limited. This study aimed to develop a closed-loop feedback system involving a new die set for nonstop mass production using a transfer press machine and to demonstrate its effectiveness in the real production of millions of pieces. Displacement and load sensors were embedded in the die set to monitor the product dimension and status of the upsetting punch. An actuator was also installed to adjust the product dimension controlled by threshold-type discrete feedback. Complex wiring from the sensors and their power sources were replaced with dedicated wireless data and power transmission devices to improve the mountability and operability when changing the die set. In the demonstration tests, the product thickness was precisely adjusted to 0.016 mm using the actuator controlled with a feedback command of 0.02 mm. The proposed system has been successfully used for the production of more than 6.5 million pieces during the period from the middle of 2023 to the end of 2025, demonstrating good durability and practicality. To detect a partial punch fracture, the Mahalanobis method is effective even when the fracture area is relatively small. To apply this method when a step-like change in the Mahalanobis distance is inevitable owing to interruptions according to the production schedule, the training data of the first several hundreds of shots need to be used for the production schedules.