Detection of Scrap Floating in a Press Die Using Accelerometers and Autoencoder

Scrap floating in the stamping die was detected using four acceleration sensors at different locations on the outer surface of the die set. First, a test without scrap-floating was performed 110 times to collect normal samples. Next, anomaly sample tests were conducted 21 times, in which the scrap was positioned such that it only impacted the top of the punch and not the stripper plate. An auto-encoder was used for detection from the accelerometer signal. The results were compared with those obtained by a previously developed anomaly detection system using the Mahalanobis-Taguchi method. The previous system obtained 80.0~98.5% of the correct answers; however, the system was not good at detecting cases where the foreign object did not impact the stripper plate. In contrast, the newer system with the auto-encoder achieved 97.7~98.5%, a high percentage of correct responses regardless of sensor position.