Place the gate at the thickest section of the part first — this ensures material reaches the mold cavity before it cools. On the thickest section, place the gate at a non-cosmetic surface (preferably an edge or internal surface) where the gate vestige will not be visible or functional. Avoid placing the gate near thin walls — the high shear at the gate can cause burn marks or binder degradation in thin sections.
Gate location rules in priority order:
| Priority | Rule | Why |
|---|---|---|
| 1 | Place gate at the thickest wall section | Ensures complete fill before freezing |
| 2 | Place gate at a non-cosmetic surface | Gate vestige will be visible — plan for it |
| 3 | Avoid placing gate near thin walls (<0.5 mm) | High shear at gate may burn or degrade material in thin sections |
| 4 | Place gate to balance flow paths | Flow should reach all extremities at approximately the same time |
| 5 | Place gate to avoid weld lines at structural features | Weld lines are weakest where flow fronts meet |
| 6 | Consider multiple gates for long parts | Reduces flow length and injection pressure |
| 7 | Place gate so the part stays on the ejection side | Part shrinks toward the gate — affects mold release |
| Gate Configuration | Weld Line Location | Strength Impact |
|---|---|---|
| Single gate, no core | No weld line | No issue |
| Single gate, one core pin | One weld line behind the core pin | 60-80% of full strength at weld line |
| Two gates | Two flow fronts meet at the center | 60-80% strength at the weld line |
| Multiple gates | Multiple weld lines | Move weld lines to low-stress areas |
- Identify the thickest section of the part → Place gate there
- Check if that surface is cosmetic → If yes, move gate to nearest non-cosmetic edge
- Check flow path to farthest cavity point → If too long (>50 mm from gate), consider second gate
- Check for core pins that create weld lines → If weld line falls on a structural feature, relocate gate or redesign the feature