Cold Runner Mold Quote Checklist: Sprue Balance and Material Waste Trade-offs

A cold runner mold quote that only states cavity count skips the runner layout decisions that drive both fill balance and how much resin is wasted every cycle. This checklist lists what to send before a cold runner tooling quote.

Runner layout and cavity balance

A naturally balanced runner layout fills all cavities evenly by geometry alone, while an artificially balanced layout relies on runner sizing to compensate for uneven cavity distances.

• Naturally balanced versus artificially balanced runner layout.
• Fill time variation tolerance across cavities.
• Runner diameter and its effect on fill balance.

Material waste and regrind strategy

Runner and sprue weight is scrapped or reground every cycle, so the waste percentage should be weighed against tooling cost before choosing a cold runner.

• Runner and sprue weight as a percentage of shot weight.
• Whether regrind can be blended back into production.
• Resin cost impact of waste percentage at target volume.

When hot runner becomes worth the added cost

At high enough volume or with expensive resin, the waste saved by a hot runner can offset its higher tooling cost within a predictable number of shots.

• Expected annual volume and total shot count.
• Breakeven point where hot runner tooling cost is offset by waste savings.
• Cosmetic requirements that may rule out a visible cold runner gate mark.