Pin-Point Gates in Injection Molds
The pin-point gate (also called a needle valve gate or pinpoint gate) is a widely used gating method in injection molds. Its small, concentrated gate size makes it ideal for precision parts with high aesthetic requirements and minimal post-processing allowances.
I. Definition and Characteristics
Definition: A small cylindrical channel (typically CNC-machined on the parting surface) forms a "point-like" gate through which molten material enters the cavity. It is often paired with a needle valve sleeve but can also serve as a standard fixed-position gate.
Key Features:
Small gate size (diameter Ø0.5–Ø2.5 mm), leaving minimal residual marks after gate trimming.
Reduced metal contact with molten material, enabling better packing pressure and denser internal part structures.
Ideal for high-gloss parts or precision components requiring hidden gate marks.
II. Design Guidelines
1. Gate Location Selection
Place in thick-walled sections or near reinforcing rib roots to ensure smooth material flow and adequate packing.
Avoid decorative or load-bearing surfaces; position on non-visible areas or recessed regions.
Align with the flow direction to minimize stagnation and flow resistance.
2. Gate Length and Angle
Gate depth (mold side thickness): 1.5–2.0 mm for structural integrity.
Ensure smooth transitions between gate walls and runners to eliminate sharp angles.
For needle valve sleeves, maintain a clearance of 0.02–0.05 mm between the needle and sleeve.
3. Runner Design
Use radiused rectangular or semi-circular cross-sections for runners connecting the manifold to the gate. The runner’s cross-sectional area should be 4–6 times the gate area.
Minimize runner length while ensuring adequate mold venting and ease of resin purging.
4. Venting and Cooling
Add vent grooves or venting pins near the gate to prevent gas traps and flow marks.
For thin-walled parts with high flow rates, position cooling channels close to the parting surface and runners to ensure uniform temperature control.
