MACHIINERY | DIE DEVELOPMENTS
Right: Reifenhauser’s PAM dies use mechatronic actuators
adjust the feed block and die
setting and regulating the flexible die lip. Depend- ing on the die design, it is also possible to autono- mously adjust the dust bar, width adjustment and lip opening by adjusting the lower die lip. It is available for all new Reifenhäuser flat dies and as a retrofit for dies from all third-party manufacturers.
Cool operation At Chinaplas, Reifenhäuser’s Kdesign subsidiary – a specialist in cooling, measuring, and calibration systems for blown film lines – showcased its Karat cooling ring. With a claimed output capacity of 50% higher than mid-range products and 25% higher than high-end competi- tors, it enables an increase in productivity, while maintaining profile tolerances and film quality. Kdesign also offers secondary cooling units.
With Centro-Freeze, producers avoid film blocking in the haul-off by cooling the bubble before it enters the flattening process. Output is further increased, while producers save on anti-block additives and improve film properties.
Lighter dies The Institute for Plastics Processing (IKV) in Germany is researching methods to reduce the weight of film extrusion dies. It says that using lightweight construction will
reduce mass, flow paths and thermal set-up times – leading to increased efficiency in film production. The project promises customised solutions for different tool sizes and types, says IKV. Extrusion dies are typically very large and heavy.
A combination of high pressure (due to the high viscosity of the processed polymers), multiple flow channels and large film widths subjects the moulds to high mechanical loads. Their large volume and high mass can cause difficulties in handling, high flow path lengths and long thermal set-up times. A research project, called ‘Automated simula- tion-driven analysis of lightweight design strategies for the efficient design of film extrusion dies, will investigate which design strategies will most effectively reduce masses, flow paths and thermal set-up times depending on the size and type of extrusion die. To do this, IKV will create a simulation environ-
ment that describes the interaction between the flow in the flow channel and the bending of the die plates. The simulation environment must also allow for an automatic adaption of plate geometry – which will be modelled using OpenFoam software. Conventional calculation methods and labora- tory tests with a flexible mould made of PMMA are
38 FILM & SHEET EXTRUSION | June 2025
IMAGE: REIFENHAUSER
used to validate this approach. Lightweight construction strategies – such as replacing steel with aluminium or increasing rigidity by bending – are then applied. Two different types of extrusion dies in various sizes will be investigated. Simulated improvements in terms of die mass, flow path length and thermal set-up time will be analysed and compared with typical industrial values. “As a result, the extent to which lightweight construction makes sense for the majority of extrusion dies used in practice will be examined for the first time,” said IKV. Two optimised dies will then be manufactured
and examined, so the optimisation method is validated alongside the calculation method. The two-year project runs until the end of this year.
Optimised design Meanwhile, rwesearchers at Wuchang Shouyi University in China have designed a new spiral die head – and analysed the flow field dynamics – to optimise film production. The researchers used fluid mechanics principles to create a mathematical model based on the die head’s structure and material properties. By varying parameters such as inlet flow rate, buffer groove length, shaping section length and non-Newtonian index, the velocity and pressure fields could be analysed using the finite element method. This showed that increasing the inlet velocity and non-Newtonian index significantly affected velocity uniformity, inlet and outlet pressure, and pressure drop. A higher inlet velocity increased fluctuations in outlet velocity and then inlet pressure; a higher non-Newtonian index led to a more uniform outlet velocity and reduced fluctuation – though with a higher inlet pressure and flow channel pressure drop. Lengthening the buffer groove and shaping section had little effect on outlet velocity uniformity,
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