Common Types of Injection Molding Gates
- Sprue Gate (Direct Gate)
Structure: The main runner directly connects to the cavity with a short flow path and large cross-section.
Automotive Applications: Large thick-walled parts, such as front/rear bumper bodies, instrument panel bases; suitable for glass fiber reinforced materials with poor fluidity.
Advantages: Low pressure loss, fast filling, less short shot.
Disadvantages: Large gate mark, requiring secondary processing; not applicable for appearance surfaces.
- Edge Gate (Side Gate)
Structure: Located on the parting surface, feeding from the side/edge of the product.
Automotive Applications: Door trim panels, pillar trims, rearview mirror housings (non-A surfaces), air outlet frames.
Advantages: Simple structure, low processing cost, flexible position to avoid appearance areas.
Disadvantages: Manual gate trimming required, with small scars on the edge.
- Pin-Point Gate
Structure: Small circular gate (usually φ0.8–1.5mm), three-plate mold structure, automatically broken during mold opening.
Automotive Applications: Central control panels, display frames, high-gloss Interior parts, small functional buttons.
Advantages: Minimal gate mark, ideal for high appearance requirements, high degree of automation.
Disadvantages: High cost of three-plate molds, slightly higher injection pressure required.
- Submarine Gate (Tunnel Gate)
Structure: Gate hidden inside the product, ribs or ejector pins, automatically cut off during mold opening/ejection.
Automotive Applications: Door handles, interior clips, trims, instrument panel buttons (full appearance without trace requirements).
Advantages: No exposed gate mark, no post-processing required, suitable for automatic production lines.
Disadvantages: Requirements for plastic part structure, reserved tunnel space needed, prone to flow marks.
- Fan Gate
Structure: Flat fan-shaped gate with width much larger than thickness.
Automotive Applications: Large-area thin-walled parts, such as roof interior panels, large door panels, light-transmitting lamp shades.
Advantages: Uniform feeding, effectively reducing weld lines and jetting marks.
Disadvantages: Large gate area, with marks after trimming.