Control strategy for cascade injection moulding with servo-electric hot runner pins
Cascade injection moulding is the preferred method for manufacturing parts with long flow paths and no visible weld lines. To compensate for process fluctuations, such as the processing of different material batches, the KaskaRe project resulted in the development of a cavity pressure control system. This regulates the pressure transfer into the cavity at each gate. The pressure transfer is adjusted by means of variable opening strokes of the hot runner valve pins.
To improve control quality, the geometries of the pin guide and the valve pin were numerically optimised in a first step, so that the correlation between opening stroke and pressure loss was linearised (Fig. 1). The optimisation was based on a physical process model describing the system behaviour. The improved control quality allows further increases in process consistency.
The pin movement was designed first for the development of the internal cavity pressure control for cascade injection moulding. Since filling is performed via several gates, the pressure transfer into the cavity can also be individually influenced at each of the gates. Injection moulding simulations were used to analyse the influence of individual pin movements on the pressure and temperature distribution in the cavity. Since the pin movements only influence the process conditions in areas close to the nozzle due to material cooling during sequential filling, all pins are moved equally for control purposes. The application of the control system increases process consistency in cascade injection moulding.
© IKVProject data and funding
We would like to thank the BMWE for funding the IGF project (funding code 22805 N) and the project partners for their cooperation.
Project duration: 01.03.2023 – 31.07.2025
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