Regelung des Werkstoffflusses zur Erhöhung der Bauteilqualität beim Rotationszugbiegen

Rotary draw bending is a forming process used for bending tubular profiles with small wall thicknesses and small bending radii. Wrinkling as a process boundary is an instability that can only be calculated to a limited extent due to the variety of influences. Up to now, only experienced machine operators designed the bending process to be wrinkle-free by carrying out adjustment trials. If corrections are made to prevent wrinkles, there is a risk that the process will lead to cracking. In this work, a knowledge-based method is presented that automatically prevents wrinkling during the bending process. A fuzzy controller was implemented that allows dosed parameter corrections to prevent wrinkles while considering the risk of cracking. Countermeasures to prevent the wrinkles are introduced as much as necessary and as little as possible. In-situ measurement systems detect the first wrinkle as it forms. Both moving the pressure die toward the tube and reducing the feed rate of the transport unit counteract the wrinkles and serve as actuators of the controller. Experience-based knowledge was integrated in the development of the control system. The derived process model can be applied to other problem solving systems, such as case-based reasoning systems, in addition to the system of a closed-loop control. In practical bending tests to prove the controller, wrinkle-free tube bends were produced. The controller, which is integrated into the machine and permanently activated, reacts to fluctuations caused, for example, by temperature fluctuations, batch changes and changes in the bending task. The use of the controller eliminates time-consuming and cost-intensive adjustment trials and reduces the reject rate. The targeted process control avoids unnecessarily high tool forces, which can reduce tool wear.