Hook Gate (Banana Gate / Tab Gate) in Injection Molds

The hook gate, commonly known as a banana gate or tab gate, is a specialized type of indirect gate used in plastic injection molding. Its core design features a curved runner (shaped like a banana or hook) concealed on the side or back of the part. This allows the melt to buffer and change direction before entering the cavity, and it is designed to break off automatically during mold opening or with minimal post-processing.

Key Characteristics and Advantages:

1. Excellent Part Appearance: The gate leaves minimal,隐蔽的痕迹 on non-cosmetic surfaces and prevents jetting marks by ensuring smooth cavity filling—critical for transparent parts.

2. Enhanced Product Quality: It reduces internal stress and warpage, improving optical properties and dimensional stability for demanding applications.

3. Ideal for Specialized Applications: Particularly suited for high-clarity flat parts like lenses, light guides, and panels (using materials like PMMA, PC), and for components where gate vestige is unacceptable.

Design for Manufacturability (DFM) Considerations:

• Gate Placement: Must be located in non-critical aesthetic or functional areas (e.g., side walls, behind ribs).

• Dimensional Control: The curved runner and gate land dimensions must ensure proper flow and clean breakage. Typical runner diameters range from φ2-φ4mm.

• Mold Structure: Requires complex machining of specialized slider or insert blocks and a reliable break-off mechanism, impacting mould DFM design and cost.

Disadvantages and Challenges:

• Higher Mold Cost: Increased complexity in plastic injection mold design and manufacturing.

• Post-Processing: May require secondary trimming, challenging full automation.

• Material Waste: The curved runner adds to scrap (regrind) volume.

• Process Complexity: Requires careful balancing of filling and cooling parameters.

Application in Key Industries:
This gate type is a premium choice in plastic molding design where performance outweighs cost considerations. It is frequently specified in automotive mold applications for high-quality interior lenses, light pipes, and exterior trim parts where appearance and reliability are paramount. It is also standard for consumer electronics and optical components.

Conclusion:
The hook gate is a specialized solution in molding for achieving superior surface finish and low stress in transparent or high-appearance parts. Its implementation requires a collaborative mould DFM design review by product designers, mold engineers, and process technicians to balance aesthetics, part performance, mold cost, and production efficiency effectively.