On the Use of COMSOL Multiphysics® to Understand and Optimize the Filling Phase in Injection and Micro-Injection Molding

Keywords

Diphasic Flow, Level-Set Method, Injection and Micro-Injection Molding, Polymer, Plasturgy
 

Context / Goal

Polymer Injection molding is a classical industrial process. However, new applications in plastronics (a mix between plasturgy and electronics) or in bioengineering make it necessary to mold very small details (microscopic scale), and thus, to call into question existing technologies and production processes.


In plasturgy, some specialized numerical softwares can be used to predict the flow in classical configurations. However, these softwares, generally based on VOF methods, reach their limits when you have to deal with high surface tension coefficients or polymer injection with micro-details.


Therefore, The European Plasturgy Pole (PEP in French) has asked SIMTEC to develop a new numerical model with COMSOL Multiphysics®. The goal of this model is to simulate a polymer filling of a mold with microdetails. An optimization of the position of the cooling channels has been performed to minimize the duration needed between two passes.
 

SIMTEC's Achievements / Results

The first mission of SIMTEC has been to visit the CLIENT on-site to visualize industrial plasturgy installation and to work on the specifications together with the CLIENT. A level-set method has been chosen in order to model the filling of the mold. This approach enables us to take into consideration the surface tension between polymer and air, and the influence of shear rate or temperature on the polymer flow.

The study has consisted of developing a model coupling:

  • The diphasic flow with the level-set method. Non-Newtonian fluids have been taken into consideration with the dependency on the shear rate through Cross-WLF law and on the temperature through Arrhenius law.
  • Heat transfer when we have optimized the cooling channels positions.

Special attention has been paid to optimize the solving time for numerical parameters (mesh, solvers) and to facilitate the numerical convergence.

Thanks to these results, we can study the influence of surface tension coefficient according to the velocity. In addition, this study has enabled us to understand the influence of experimental parameters on polymer propagation. This is a key point for reaching top quality molded pieces.