Plastic Injection Molding Gate Types

In plastic injection molding, the gate is the entry point through which molten plastic flows into the mold cavity. The design and location of the gate significantly impact part quality, cycle time, and mold performance. Here are the main types of gates used in injection molding:

1. Edge Gate (Side Gate)

• Location: On the parting line, at the edge of the part.

• Usage: Most common gate type.

• Advantages:

• Easy to design and machine.

• Good for flat or simple parts.

• Disadvantages:

• Can leave a visible mark.

• May cause uneven filling in thick parts.

2. Submarine Gate (Tunnel Gate)

• Location: Below the parting line, enters at an angle.

• Usage: Automatically shears off during ejection.

• Advantages:

• Automatic degating.

• Hidden gate vestige.

• Disadvantages:

• Harder to machine.

• Limited to small/medium parts.

3. Pin Gate (Direct Gate)

• Location: Directly in the center of the part (used in 3-plate molds).

• Usage: Often used for symmetrical parts.

• Advantages:

• Excellent flow and packing.

• Good for round or disk-shaped parts.

• Disadvantages:

• Gate mark at the center.

• Requires 3-plate mold (higher cost).

4. Fan Gate

• Location: Edge of the part but spread in width.

• Usage: Large flat parts needing uniform flow.

• Advantages:

• Uniform filling.

• Reduces stress and warpage.

• Disadvantages:

• More complex design.

• Slower cooling.

5. Tab Gate

• Location: On edge, with a tab between gate and part.

• Usage: Reduces shear stress for fragile or cosmetic parts.

• Advantages:

• Prevents jetting.

• Good for large or thin parts.

• Disadvantages:

• More material used.

• Extra trimming needed.

6. Hot Tip Gate

• Location: Direct center, used with hot runner system.

• Usage: Best for center gating on circular parts.

• Advantages:

• No runners (material savings).

• Good for high-volume production.

• Disadvantages:

• Expensive system.

• Risk of gate vestige (visible dot).

✅ Gate Selection Considerations:

When choosing a gate type, consider:

• Part geometry

• Material flow characteristics

• Cosmetic requirements

• Mold complexity

• Cycle time and production volume