Key principles.
Standard
Plastic in runners cools, ejected with part. Trimmed.
Premium
Heated runners keep material molten. No waste. Faster cycle.
Standard
Gate at edge of part. Visible mark on edge.
Hidden
Tunnel through mold to cavity. Mark hidden inside.
Hot runner
Small precise gate from hot runner. Auto-trimmed.
Buried
Gate buried, breaks off cleanly. Low scarring.
FAQ
Avoid cosmetic surfaces. Allow uniform fill. Far from mating surfaces. Discuss with tooling engineer.
Hot: $5-20K premium tool. No runner waste. Faster cycle. Cold: cheaper, slower, runner becomes scrap.
Cold runner gates leave visible mark. Hot runner pin gates almost invisible. Tunnel/submarine gates hide.
Mold flow simulation predicts fill. Identifies issues before tooling. Premium service for complex parts.
Smaller gate: more shear, faster cooling, harder to fill. Larger gate: easier fill, slower cycle, larger scar.
Balanced runner system equal flow to all cavities. Critical for consistent parts.
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