In extrusion blow moulding, swelling and elongation effects significantly influence the geometry of the parison and thus the wall thickness distribution in the component. IKV has developed a simulation model to predict these effects on the basis of viscoelastic material models, in particular the Phan-Thien-Tanner model (PTT).
Data from high-pressure capillary rheometers (HPCR) were used for the model calibration. The parameterisation of the PTT model was automated using the DAKOTA optimisation software. Simulations with OpenFOAM and the rheoTool enabled a realistic prediction of the threshold behaviour for the first time, even at high throughputs (up to 50 kg).
© IKVInitial results show that throughput and nozzle geometry have a significant influence on the swelling behaviour. The models provide good agreement with experimental data. A newly developed inline rheometer was used to calibrate the simulation results. It measures the shear and extensional viscosity during production using pressure sensors in defined positions in the flow channel.
In the long run, the method should enable adaptive process control in order to compensate for quality fluctuations due to material variations – for example through the use of recycled materials. An extension of the simulation environment to take active wall thickness control into account has already been implemented, so that it can also be transferred to industrial applications. The aim is to provide practical support for operators and plant engineers with a digital tool for active process control and quality assurance.
Project data and funding
We would like to thank the BMWE for funding the IGF project (funding code 22731 N) and the project partners for their cooperation.
Project duration: 01.06.2025 – 31.05.2025
Promotion:
