Simulation of Jetting in Injection Molding Using a Finite Volume Method

Area of Science:

• Polymer Science
• Computational Fluid Dynamics
• Materials Engineering

Background:

• Accurate prediction of melt flow behavior, including jetting and buckling, is crucial for optimizing plastic injection molding processes.
• Existing models may not fully capture the complex interplay of forces governing non-isothermal, incompressible fluid dynamics during mold filling.

Purpose of the Study:

• To develop and validate a three-dimensional computational model for predicting jetting and buckling flow in polymer processing.
• To investigate the influence of process parameters such as injection speed, melt temperature, and gate location on melt front progression.

Main Methods:

• Establishment of a three-dimensional melt flow model for viscous, incompressible, and non-isothermal fluids.
• Discretization of governing equations using a control volume-based finite volume method.
• Implementation of a two-fold iterative approach to decouple pressure, velocity, and temperature dependencies for enhanced numerical stability and reduced computation.

Main Results:

• The filling pattern is determined by the balance between inertial and viscous forces; jetting occurs when inertial forces dominate, transitioning to buckling flow as viscous forces become more significant.
• Jetting length was found to increase with injection speed but showed minimal variation with melt temperature.
• Simulated results demonstrated reasonable agreement with experimental data for jetting length and buckling frequency.

Conclusions:

• The developed numerical model and method are effective for simulating jetting phenomena in polymer melt flow.
• Understanding the competition between inertial and viscous forces is key to controlling jetting and buckling during injection molding.
• The simulation provides valuable insights for process optimization and defect prevention in plastic manufacturing.