How to Effectively Balance Runners in Multi-Cavity Molds?
In multi-cavity mold design, runner balance directly impacts filling uniformity across cavities and the consistency of product quality.
1. Runner Structure Design Optimization
Symmetrical Layout and Geometric Matching
Adopt a symmetrical structure during mold design to ensure uniformity in geometric parameters (e.g., length, cross-sectional area, bends) of the main and sub-runners for each cavity. Symmetrical layouts minimize filling imbalances caused by path variations.
Rational Main and Sub-Runner Configuration
The main runner, as the core distributor of molten material, must minimize flow resistance. Sub-runners should be designed with similar resistance levels to prevent underfilling in cavities with higher resistance. The "equivalent runner theory" can be applied by adjusting cross-sectional areas or lengths to compensate for minor discrepancies.
2. Runner Resistance Control
Adjusting Cross-Section and Length
CAE simulation can precisely estimate flow resistance in different runners during production. Based on simulation data, designers can modify cross-sectional areas or lengths to address imbalances caused by runner geometry, ensuring uniform resistance across cavities.
Auxiliary Balancing Measures
For molds where full symmetry is impractical, balancing devices (e.g., flow restrictors) can be integrated into runners. These components adjust localized flow pressure to equalize melt distribution among cavities.
3. Addressing Venting Challenges
Designing Effective Venting Channels
Runner balancing extends beyond pressure distribution—venting is equally critical. Proper venting systems ensure air is promptly vented during filling, preventing gas entrapment that disrupts uniformity. In multi-cavity molds, venting channels must cover all cavities, particularly at runner transitions, to guarantee unobstructed airflow.
