Analysis of a new process for continuous hot extrusion utilizing the theory of similarity
Final Report Abstract
Continuous extrusion is a combination of direct and indirect extrusion with a stationary or movable valve. The material is pressed from the first container with a direct ram through the valve into a second container. The material can be extruded indirectly from the second container using a hollow ram with the extrusion die. The valve only allows the material to flow in the extrusion direction, which means that the material can be continuously extruded from the second container while the next billet is loaded into the first container. The exit speed can be kept constant over the entire cycle and the usual standstill during billet-on-billet extrusion is avoided. As there is currently no machine for continuous hot extrusion, the process was investigated using the method of similarity with a physical model, substitute experiments with aluminium and numerical methods. The functionality of the stationary valve could be proven with substitute experiments with aluminium. As the ram and hollow ram cannot be moved independently of each other in the substitute experiments, a model of a continuous extrusion press was developed with plasticine as the model material. Here, the ram and hollow ram can be controlled independently of each other and continuous extrusion cycles can be conducted. By numerical modelling, process windows can be established for continuous extrusion with movable and stationary valves. Even for alloys that are hard to extrude (in this case EN AW-7075), a continuous profile exit can be achieved with both variants without reaching the solidus temperature or exceeding the permissible ram load. Numerical and analytic methods have shown that the welding of the transverse press seam can be significantly improved.
Publications
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14th International Conference on the Technology of Plasticity, 25.09.2023, Comparison of Stationary and Movable Valves for Continuous Hot Extrusion
J. Gebhard
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72nd CIRP General Assembly, 23.08.2023, Comparison of Stationary and Movable Valves for Continuous Hot Extrusion
J. Gebhard
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Aluminium Praxis 12/2023 (4. Dezember 2023): Innovationen im Bereich Strangpressen
Gebhard, J.; Kotzyba, P.; Tekkaya & A. Erman
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Comparison of Stationary and Movable Valves for Continuous Hot Extrusion. Lecture Notes in Mechanical Engineering, 450-458. Springer Nature Switzerland.
Gebhard, Johannes; Schulze, André & Tekkaya, A. Erman
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Continuous hot extrusion with a stationary valve. CIRP Annals, 72(1), 237-240.
Gebhard, Johannes; Schulze, André; Clausmeyer, Till & Tekkaya, A. Erman
