Integrated sensing system for stamping monitoring control

This paper investigates the feasibility of integrating a draw-in sensor and an array of force sensors under sheet metal tooling surface for the on-line monitoring of stamping operations. The draw-in sensor was developed based on the mutual inductance principle and provided linear results between the draw-in of the tested sheet metal and the induced voltages. The draw-in sensor was tested to simulate the stamping environment. To validate the experimental results, the draw-in sensor tests were compared to both the analytical and the simulation methods and the results were in agreement. Currently, the draw-in sensor is being implemented in a hydraulic stamping press to observe the functionality and accuracy of the draw-in sensor. This paper identifies a new approach to process monitoring in stamping processes by embedding force sensors into the stamping tooling structure. It is aimed to detect stamping process defects through identifying patterns of forming pressure variations. Towards this end experiments were conducted on a stamping test-bed equipped with an array of force sensors. Measurements from the spatially distributed sensors were used to numerically interpolate the pressure distribution at any point on the tooling surface by Thin Plates Splines. The combined accuracy of the physical sensing system and the surface generation technique has been estimated by comparing press force calculated from numerical integration of the TPS determined pressure surfaces with direct measurements.