Abstract
In order to not only produce an open-die forged part with the desired final geometry but to also maintain economic production, precise process planning is necessary. However, due to the incremental forming of the billet, often with several hundred strokes, the process design is arbitrarily complicated and, even today, often only based on experience or simple mathematical models describing the geometry development. Hence, in this paper, fast process models were merged with a double deep Q-learning algorithm to enable a pass schedule design including multi-objective optimization. The presented implementation of a double deep Q-learning algorithm was successfully trained on an industrial-scale forging process and converged stably against high reward values. The generated pass schedules reliably produced the desired final ingot geometry, utilized the available press force well without exceeding plant limits, and, at the same time, minimized the number of passes. Finally, a forging experiment was performed at the institute of metal forming to validate the generated results. Overall, a proof of concept for the pass schedule design in open-die forging via double deep Q-learning was achieved which opens various starting points for future work.
Highlights
After the development of an alternative spread equation and the implementation into the pass schedule calculation, the geometry model achieved an accuracy of 2% [5]
The fast process models for open-die forging presented in Section 2.1 open the possibility to predict the process and workpiece properties that result from a pass schedule quickly and, to include the workpiece properties directly in the pass schedule design
The algorithm converged reliably in all training scenarios. This shows that the selected algorithm and its hyperparameters are well suited for the introduced problem of pass schedule design in open-die forging and, at the same time, emphasizes the transferability of the presented approach
Summary
Open-die forging is an incremental forming process to produce predominantly longitudinally oriented components such as turbine shafts. Pass schedule calculation programs can improve on this by including the geometry development and other workpiece and process parameters, such as temperature, deformation resistance, or press force, in the pass schedule design. The program is able to determine the workpiece dimensions depending on the material, the temperature as well as height reduction and manipulator feed It is checked whether the forming forces exceed the maximum press force. Pass schedules calculated with ForgeBase can be used directly to control the open-die forging plant during the process, whereby the press operator can select freely between either fully automatic, semi-automatic, or manual mode. The simple functionality of the program implemented in MathWorks MATLAB was expanded by the informative graphical representation of individual strokes
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