Development of inline closed-loop vibration control in progressive die stamping using finite element simulation

Abstract

Modern progressive dies are increasingly equipped with integrated sensors and actuators, thus enabling an improvement of the manufacturing process and an inline monitoring of the component quality. The design of the tooling is determined at an early stage and is largely based on the desired product and the specific production stages such as blanking, forming and punching. Nevertheless, malfunctions such as strip vibrations cannot always be foreseen and may occur during operation time, which may lead to reduced component quality and in the worst case to component collision or a damage of the tooling. Therefore, complex reworking or a reduction of the stroke rate and thus lower output quantity are often necessary for a reliable and stable process. Strip vibrations are often caused by the highly dynamic transportation of the strip in the tool and can have various causes. Among others, passive tooling components such as spring-loaded, hard stop limited strip lifter can be the cause of such vibrations. Strip lifter are always necessary when three-dimensional components are produced and have to be lifted out of the die for the feeding phase. The feeding phase takes place between two strokes of the stamping process. This work is aiming for a control strategy to suppress strip vibrations in various progressive die stamping processes based on closed-loop controlled active strip lifter. These strip lifter combine the spring-loaded passive standard strip lifter with an additional PID-controlled actuator. Taking the dynamics of the flexible strip during operation into account, a Finite Element Analysis (FEA) model of a progressive die tooling system is created. For the design of the control algorithm, the FEA model is connected to an environment for model-based design in a co-simulation. This approach allows modelling the influence of arbitrary control parameter settings on the movement curve of the strip, aiming for an increased stroke rate.

A Data-Based Tool Failure Prevention Approach in Progressive Die Stamping

“…Another problem connected to data-driven approaches is that in real industrial cases, signals may shift for reasons that are often unknown and lead to conditions that are "false positives", i.e., conditions that apparently indicate an anomaly but that eventually correspond to regular production with good quality and no evidently worn or failed tools. Indeed, many sources of variability affect progressive die stamping, including material variations (thickness and properties), strip vibrations [33], piloting imprecisions [34] and many others. Another relevant issue connected with the progressive die stamping of small metal parts is the inherent difficulty of observing and measuring the progression of die wear in real industrial environments [35].…”