Injection Molding Simulation
Design for Manufacturing
This project used Moldex3D to evaluate gate placement, runner design, and process settings for a simplified LEGO brick. I compared two materials, ran simulations across multiple designs, and identified the central pin gate with extended packing time as the most effective setup. The final conditions produced more uniform density, reduced shrinkage, and fewer weld lines, highlighting how simulation-driven decisions can improve injection-molded part quality.
April 2023
My Roles: Material Analysis, Moldex3D Simulations, Analysis
The Process
Initial Geometry & Material Analysis
The team selected a simplified LEGO brick as the test geometry.
Two materials were evaluated—HDPE and ABS—based on melt flow index, softening temperature, cost, elongation, and tensile strength. After comparing properties, ABS was selected for its stiffness, temperature resistance, and suitability for accurate molding in simulation.
Skills & Tools: Material Analysis
Gate and Runner Design
Two pin gate configurations were evaluated to compare filling behavior and part quality:
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Central Pin Gate: Filled horizontally and produced more uniform flow, leading to consistent density and fewer problematic weld lines.
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Corner Pin Gate: Filled diagonally, which shifted weld lines to more visible areas and created less uniform heat flux.
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Across both designs, pin gates were chosen for low gate vestige and improved cosmetic quality. The simulation results confirmed that the central gate was the most effective.
Skills & Tools: Moldex3D, Injection Molding Gate Design
Packing and Filling Times
To optimize internal quality, we explored variations in packing time and pressure along witth analyzing weld line differences.
A packing time of 6 seconds paired with 108.5 MPa produced:
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More uniform density
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Lower shrinkage
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Minimal shear stress
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Consistent warpage results
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Packing time had minimal impact on the initial filling pattern but significantly influenced final part uniformity.
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Skills & Tools: Moldex3D, Comparative Analysis
Results & Conclusion
Extended packing time with the central pin gate provided the most stable and uniform part conditions. The resulting simulation showed reduced shrinkage and better density balancing throughout the brick.
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Overall, this project demonstrated how Moldex3D can be used to make informed choices in injection molding design—from material selection to gate placement to process parameter tuning.