Analyzing the flexible pouch filling process

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Analyzing the filling process of a flexible pouch

ㆍ Product: Flexible pouch filled with liquid detergent / pouch filling machine

ㆍ Analysis Goal: Investigating the effects of both design and process parameters to select the optimal machine configuration for the flexible pouch filling process

Packaging companies expend significant effort to develop machines whose performance is expected to remain high and consistent even if the packaged goods, the packaging format, or the packaging material change. In the case study presented here, Coesia S.p.A., which is a leading multi-national packaging company headquartered in Italy, partnered with both EnginSoft S.p.A. and the University of Trento to simulate the full process through which a stand-up pouch is created, filled with liquid, and sealed in a Doypack® packaging machine. This challenging activity required the development of a multi-physics digital prototype of the machine-package-fluid system. In particular, the two-way coupling between multi flexible body dynamics and particle-based fluid dynamics was set up to properly replicate the interactions between fluid and a flexible pouch in dynamic conditions.

Process

① Most components are modeled as rigid bodies. (i.e., clamps, suction cups, nozzle, and shutter)

② The pouch is modeled as a deformable, flexible body capable of large deformation. (4-node, 6-DOF-per-node shell elements are used to represent the thin film.)

③ All stages of the process are simulated. (opening, filling, closing, and sloshing)

④ The modeling of the flexible pouch is fully automated using RecurDyn/ProcessNet, allowing the creation of multiple types of pouches in a short time.

⑤ A two-way-coupled co-simulation between RecurDyn and Particleworks is used to obtain a reliable representation of the Fluid-Structure Interaction. (FSI).

⑥ Experimental data is used for model validation. The optimal particle size and other numerical parameters have been set to balance model reliability and CPU time.

A. Opening, B. Filling, C. Closing and Filling process of the pouch

Flexible pouch filling process

Key Technologies for Analysis of the flexible pouch filling process

• MFBD technology to handle the non-linearities due to both large displacements and extended frictional contacts of the flexible pouch

• Meshless particle-based CFD that is well suited to the free-surface flows such as injection or sloshing of liquids

• Seamless interface between RecurDyn and Particleworks for easy and accurate simulation of the Fluid-structure interaction (FSI)

Toolkits for the flexible pouch filling process simulation

RecurDyn/Professional
RecurDyn/FFlex
RecurDyn/ProcessNet
Particleworks Interface

Customer Challenges

• Understand the relationship between design and stability of the bottom gusset, which prevents the refolding of the pouch during pouch filling operations.

• Identify the best design and process parameters through repetitive modeling and reasonably short simulations.

• Include the non-Newtonian behavior of the injected liquid, which affects the overall response of the flexible pouch.

• Make sure that, even in dynamic conditions, the fluid level does not exceed a predefined limit to ensure that the sealing area remains clean during operations.

• Consider the interaction between fluids and flexible moving structures.

Solutions for the flexible pouch filling analysis

RecurDyn MFBD technology is used that can simulate both rigid and flexible bodies in motion together.
RecurDyn/ProcessNet provides the script to automate modeling and meshing for easy DOE.
Co-simulation between RecurDyn and Particleworks can calculate the interaction between the fluid and flexible pouch.

Stress contour before (L) and after (R) closing Parametric analysis results of the bottom gusset

Outcomes of the analysis of the flexible pouch filling process

The stability and the opened/deformed shape of the flexible pouch were reliably predicted.
The simulation results provided additional guidance about the existing relationships between material properties, film thickness, and pouch design with the stability and the opening of the pouch itself.
It has been possible to identify the proper thickness and the stiffness of the gusset of the pouch
The simulation results provided additional guidance about the motion laws and the performance of the pouch filling machine.
The digital model was able to provide some key information that could not be retrieved by performing classic physical testing.
The entire simulation took about 10 hours in a regular workstation featuring a GPU. This allowed multiple investigations overnight without the need of HPC.