How Gating and Runner Design Affects Die Cast Part Quality

The design of the gating and runner system in die casting is like a part’s circulatory system—it controls how molten metal flows into the cavity.

Done correctly, it enables smooth filling, prevents defects, and extends tool life.

Done poorly, it causes porosity, cold shuts, and stress points in the part.

🔄 What Are Gates and Runners?

• Runner: The main channel that delivers molten metal from the shot sleeve to multiple gates.

• Gate: The final entry point into the cavity. It controls metal velocity and fill pattern.

📐 Key Gating Considerations:

1. Metal Velocity at Entry

   Too fast = turbulence → porosity

   Too slow = incomplete fill → cold shuts

2. Gate Location

   Impacts how metal flows, traps air, and solidifies.

   Gates should avoid dead-ends or isolated features.

3. Gate Size and Shape

   Influences pressure, flow rate, and ease of gate break-off during trimming.

4. Multiple Gates vs Single Gate

   Complex parts may need balanced dual gates.

   Poor balance can cause weld lines or uneven strength.

5. Runner Length & Cross-Section

   Impacts metal temperature by the time it reaches the gate—especially in larger molds.

At LVIO Precision, we collaborate with tooling partners to simulate flow patterns using mold flow analysis. This allows us to determine optimal gate shape, runner layout, and overflow positioning—reducing first-shot failures and long-term scrap.

We know that a good part doesn’t start at the cavity—it starts with the right gate.