ExtruTeC - High Precision Extrusion Temperature Control through Digital Technology

ExtruTeC is a 4-year project that started September 1st, 2020. It is a collaboration between Hydro Extruded Solutions AS, Cybernetica AS, the R&D institute SINTEF and NTNU. The main objective of the project is to develop a digital framework for temperature control in aluminium extrusion. This involves detailed modelling of the extrusion process and digital twins interacting with temperature sensors for process optimisation and precise temperature control. The extrusion process involves complex interactions between billet material, extrusion dies and process parameters. For thin-walled profiles, such as multiport extrusions (MPE), temperature control is essential. Lack of temperature control can result in quality issues, such as surface defects like pick-ups or tearing of internal webs and reduced productivity as speed must be adjusted to avoid quality issues at too high peak exit temperatures. In the project, Cybernetica has developed and implemented model based optimising control schemes, based on their CENIT software, which make it possible to control the temperature over the press cycle to yield precise control of the peak exit temperature of thin-walled profiles. In 2021 and 2022, Cybernetica and NTNU worked with coupled models for the billet heating and temperature evolution during the extrusion process, where the effects from the measured temperature were included. These models were then installed at Hydro’s pilot press in Tønder, Denmark. In 2022 and 2023 Cybernetica optimized the cooling cycle during extrusion and included control schemes to keep constant exit temperature by controlling both the cooling and the extrusion speed. In 2022, the CENIT digital twin and control system was implemented in the pilot press in Tønder and testing in production was started in 2023. A parallel activity for the implementation of the CENIT control system was also started, and by summer 2024 five MPE profiles have been approved to be extruded, fully controlled by the CENIT control system. Plans for further testing and roll-out are being prepared. In August 2021, a PhD student was engaged at NTNU, studying further optimisations of the extrusion process. The PhD student has participated in a conference (with a conference proceeding) and has submitted one paper for publication. To complete the PhD at NTNU, the project end has been shifted to the end of 2025. Hydro has performed a number of extrusion trails at Hydro's pilot press in Tønder. This includes instrumentation for temperature measurements with thermocouples in the extrusion tool packages. Idealised laboratory cooling trials have also been done at Hydro Karmøy. A goal for these trials has been to achieve a better understanding of how the cooling of the extrusion dies influences the temperature evolution and distribution during the extrusion process and the peak exit temperature of thin-walled profiles. Trials have also been done to resolve issues with flow imbalance between different exits for certain cooling channel lay-outs. From 2023, many trials have been done for testing and validating of profiles to be approved for running under full control of the CENIT control system. Part of this validation process have included quality assessments of the different profiles, such as checking the quality of the internal webs. In 2020 and 2021, SINTEF worked with detailed models for the extrusion process (with Altair HyperXtrude) and the idealised cooling trials at Hydro Karmøy (with ANSYS Fluent). An objective was to get a better understanding of the relation between the measured temperature in the tool package and the peek exit temperatures, which cannot be measured. In 2021, SINTEF studied the effects of different cooling channel layouts on peak exit temperatures. In 2021 and 2022, SINTEF studied the effects of flow imbalance between different exits related to certain cooling channel lay-outs. In 2022 and 2023 SINTEF studied the effects of reduction ratio (from billet to profile) for different profiles on the peak exit temperature. During 2023 and 2024, transient simulations of the temperature evolution over multiple billet cycles, with and without cooling, have been done for selected profiles to be approved for the CENIT control system, to estimate the peak exit temperature for these profiles.

Hydro Extruded Solutions - Precision Tubing produces thin walled MultiPort Extrusions (MPE) and round tubes. From the market, there is a continuous strong pull towards reduced tube weight and wall thickness and stronger alloys. Over the last years the typical MPE wall thickness has been reduced from 0.45 mm to 0.20 mm. It is Hydro's strategy to work towards further wall thickness reductions, while at the same time implementing stronger alloys. However, the achievements with thinner walls and stronger alloys have led to new challenges related to local overheating and more challenging flow balance. A major reason for this is a lack of temperature control. To achieve further wall thickness reduction with stronger alloys, there is therefore demands for much tighter temperature control than what has been needed earlier. The planned innovation involves: - To achieve full temperature control for extrusion of thin walled MPE profiles. This involves both the spatial temperature distribution and the temperature evolution over the press cycle. The project will develop and implement new model based optimising control schemes: A supervisory system for batch cycle optimisation, and a rapid, high precision model predictive temperature control system. This will make it possible to control the temperature over the press cycle and yield precise control of the exit temperature of thin walled MPEs. Such temperature control represents a major step change with respect to today's process capability for MPEs. With this project, MPE has been chosen as a strategic product for establishing high precision temperature control for extruded products. There are currently close to 150 extrusion presses owned and operated by Hydro, and the temperature control developed in this project, will in the longer term be of major importance for other extrusion products and markets.