1. Introduction
Mould Flow Analysis (MFA) is a computer-aided engineering simulation used to predict how molten plastic will flow during the injection moulding process. Proper interpretation of mould flow results is essential to ensure part quality, reduce manufacturing defects, and optimize mould design and processing conditions.
2. Objectives of Mould Flow Analysis
Predict material flow behavior inside the mould cavity.
Identify potential defects (e.g., weld lines, air traps, sink marks).
Optimize gate location, number, and size.
Minimize warpage and shrinkage.
Improve cycle time and part performance.
3. Key Results & Interpretation
a. Fill Time / Flow Front
Definition: Time taken for the molten plastic to fill the cavity.
Interpretation:
Uniform flow fronts suggest balanced filling.
Uneven or erratic fronts may indicate imbalance or poor gate location.
Long fill times can cause premature cooling and incomplete fill.
b. Pressure at Fill
Definition: Pressure required to completely fill the mould.
Interpretation:
High pressure may suggest narrow flow channels, small gates, or long flow paths.
Aim for balanced pressure distribution to avoid overpacking and stress.
c. Weld Lines
Definition: Formed when two or more flow fronts meet.
Interpretation:
Common in multi-gate systems or complex geometries.
Can weaken the part structurally and aesthetically.
Location and strength should be analyzed, especially in load-bearing areas.
d. Air Traps / Venting
Definition: Areas where air can become trapped due to flow convergence.
Interpretation:
Likely defect zones—can cause burns, voids, or incomplete fill.
Add venting or modify gate location to reduce risk.
e. Temperature Distribution
Definition: Distribution of melt temperature during injection.
Interpretation:
Uneven temperature can lead to inconsistent flow or part warping.
High-temperature differences may cause residual stress.
f. Shrinkage
Definition: Dimensional reduction of the part during cooling.
Interpretation:
High shrinkage can affect part accuracy and fit.
Modify process settings or design allowances to compensate.
g. Warpage
Definition: Deformation of the part after ejection due to uneven shrinkage.
Interpretation:
Caused by material anisotropy, cooling rate differences, or part geometry.
Countermeasures: Adjust cooling, gate location, or material selection.
h. Clamping Force
Definition: Maximum force required to keep the mould closed during injection.
Interpretation:
Should be within the machine’s clamping capacity.
Excessive force may indicate design issues or high injection pressures.
4. Gate and Runner Analysis
Evaluate gate location impact on flow balance and weld line formation.
Check runner size optimization for balanced pressure and reduced waste.
5. Material Behavior Insight
Understand how selected material (viscosity, shrinkage rate, thermal properties) behaves in the mould.
Use material-specific data for better simulation accuracy.
6. Common Recommendations After MFA
Change gate location or type.
Adjust wall thickness for better flow.
Modify part geometry to eliminate weld lines.
Add cooling channels or improve existing ones.
Use alternative material with better flow properties.
7. Conclusion
Interpreting mould flow analysis correctly allows engineers to anticipate and eliminate production problems before physical mould creation. It is a proactive step in reducing cost, improving quality, and accelerating time-to-market.
