Views: 0 Author: Site Editor Publish Time: 2025-07-25 Origin: Site
The gate serves as the entry point for molten plastic into the mold cavity. Its position influences:
✔ Filling behavior – Ensures uniform flow and avoids air traps.
✔ Part strength – Affects weld line placement and stress distribution.
✔ Surface finish – Prevents flow marks, jetting, or visible gate marks.
✔ Ejection & post-processing – Determines ease of degating and finishing.
Thick sections – Helps with packing and reduces sink marks.
Non-cosmetic areas – Hides gate vestige (e.g., inside edges, hidden surfaces).
Balanced flow paths – Ensures even filling, especially in multi-cavity molds.
Away from cores & inserts – Prevents deflection or damage from high-pressure flow.
Thin walls – May cause short shots or excessive shear stress.
High-stress areas (e.g., snap fits, hinges) – Weakens mechanical properties.
Visible surfaces – Unless using micro-gates or hot runner systems.
Deep ribs or corners – Can trap air, leading to burns or incomplete filling.
Best gates: Edge gates, fan gates, or multiple point gates.
Placement: Along the longer edge for balanced flow.
Example: A smartphone case should have gates on the side or bottom to avoid front-face marks.
Best gates: Pin-point gates (top center) or submarine gates (side entry).
Placement: Avoid weld lines in load-bearing areas.
Example: A gear should use a side gate to prevent center shrinkage.
Best gates: Direct sprue gate or hot runner valve gates.
Placement: Bottom center for better packing and venting.
Best gates: Banana gates or tab gates to minimize flow marks.
Placement: Non-optical zones to prevent visible defects.
| Gate Type | Best For | Pros & Cons |
|---|---|---|
| Edge Gate | Flat parts, thick walls | ✔ Easy to modify ✖ Leaves visible mark |
| Pin-Point Gate | Small parts, multi-cavity molds | ✔ Auto-degating ✖ Requires 3-plate mold |
| Submarine Gate | Hidden gate marks (e.g., under ribs) | ✔ No manual trimming ✖ Higher wear |
| Hot Runner Gate | High-volume production | ✔ No waste ✖ Expensive maintenance |
| Fan Gate | Wide, thin parts (e.g., panels) | ✔ Reduces stress ✖ Larger vestige |
Use Moldflow simulation – Predicts flow patterns, weld lines, and air traps.
Test with short shots – Helps identify flow imbalances during trial runs.
Adjust gate size – Smaller gates reduce vestige but may increase shear stress.
Selecting the right gate location requires balancing part design, material properties, and mold functionality. By following these guidelines and leveraging simulation tools, you can minimize defects, improve part quality, and reduce production costs.
