Views: 0 Author: Site Editor Publish Time: 2025-05-09 Origin: Site
The gate is the narrow passage connecting the runner system to the mold cavity. It controls:
Flow rate of molten plastic
Pressure during filling and packing
Cooling behavior and final part quality
A well-designed gate ensures proper filling, minimizes defects, and reduces post-processing.
Different gate types are used based on part design, material, and cosmetic requirements:
Simple and cost-effective.
Requires manual trimming.
Suitable for thick-walled parts.
Small, round gate used in three-plate molds.
Automatically detaches during ejection.
Ideal for small, high-precision parts.
Angled gate that shears off during ejection.
Leaves minimal marks, good for cosmetic parts.
Wider entry to distribute flow evenly.
Reduces stress in flat or large parts.
Large opening, minimal pressure loss.
Leaves a noticeable mark, requires trimming.
Place near thick sections for better packing.
Avoid flow hesitation or jetting (visible flow marks).
Minimize weld lines in critical areas.
Too small → High pressure, incomplete filling.
Too large → Longer cooling, sink marks.
Rule of thumb: 50-80% of part thickness.
High-viscosity plastics (e.g., PC, ABS) need larger gates.
Low-viscosity plastics (e.g., PP, PE) can use smaller gates.
Ensure proper cooling near the gate to prevent warping.
Submarine gates should have a 30°–45° angle for clean breakage.
| Defect | Possible Cause | Solution |
|---|---|---|
| Sink marks | Insufficient packing | Increase holding pressure/time |
| Jetting | High speed through small gate | Use fan gate or reduce injection speed |
| Weld lines | Poor gate placement | Optimize gate location or add flow leaders |
| Gate vestige | Improper gate design | Switch to submarine or pin gate |
| Short shots | Gate too small | Increase gate size or melt temperature |
Hot Runner Gates: Eliminate runner waste, improve cycle time.
Valve Gates: Precisely control flow for multi-cavity molds.
CAE Simulation (Moldflow): Predict flow behavior before mold fabrication.
The gate is a small but crucial element in injection molding. Proper selection and design can reduce defects, improve efficiency, and lower costs. Always consider part geometry, material properties, and mold requirements when choosing a gate type.
