David Harsch

Inline feedback control for deep drawing applications

In series production of deep drawing products the quality of the parts is significantly influenced by material scatter. To guarantee a robust manufacturing the processes are designed to have a large process window. As the different material properties can lead to a drift in the process, the press settings have to be adjusted to keep the quality. In the scope of the work a feedback control system is proposed to keep the operation point inside the process window. The blank draw-in measured in predefined points is used as the primary indicator of the expected part quality. A simulation based meta model is then used to design the control algorithm with the blank holder forces as control variable. As the draw-in measurements are carried out punctually, their positioning within the tool becomes of critical importance. A simulation based study is therefore presented for the identification of sensor positions with the highest significance in relation to the process outcome. The baseline calibration of the controller is also based on the meta model. The validation of the proposed control system is illustrated based on experiments in a production line.

Process Windows for Sheet Metal Parts based on Metamodels

Achieving robust production of deep drawn sheet metal parts is challenging. The fluctuations of process and material properties often lead to robustness problems. Numerical simulations are used to validate the feasibility and to detect critical regions of a part. To enhance the consistency with the real process conditions, the measured material data and the force distribution are taken into account. The simulation metamodel contains the virtual knowledge of a particular forming process, which is determined based on a series of finite element simulations with variable input parameters. Based on the metamodels, process windows can be evaluated for different parameter configurations. This helps improving the operating point search, to adjust process settings if the process becomes unstable and to visualize the influence of arbitrary parameters on the process window.

Q-Guard - An intelligent process control system

Stainless steel is a complex material and has properties that make it difficult to use in deep drawing processes. Because of its scattering material properties a robust process is difficult to achieve, resulting in the necessity to constantly adjust the drawing process. In order to produce parts at constantly high quality and to minimize scrap production, an intelligent control system, the Q-Guard system is implemented in production, covering the whole process chain from raw material to the finished part. This control system is presented in this contribution, with the main focus on the process control. This system is based on numeric simulations as well as material data, the process settings and draw-in measurements, all of them acquired in-line in production. Part of the data is used for a feedforward control for immediate good parts production, part of the data, like the draw-in, measured with an optical measurement system after the first draw, is used in a feedback loop. The layout of the process control and results from production runs will also be shown in this work.