Hot Runner Mold & Cold Runner Mold

In plastic injection molding, hot runner molds and cold runner molds refer to two different types of runner systems used to deliver molten plastic into the mold cavities. Here's a complete comparison to help you understand their differences, advantages, disadvantages, and application scenarios:

1. Hot Runner Mould

What is it?

A hot runner mold uses a heated manifold and nozzles to keep the plastic in the runner system molten, delivering it directly to the cavities without forming solid runners.

Key Features:

• Includes heated components (manifold, nozzles).

• No solid runner is ejected with the part.

• Often used with valve gates or open tip gates.

✅ Advantages:

• ♻️ No material waste (no runner to trim or recycle).

• ⚡ Faster cycle times (no cooling time for runners).

• Better part quality (improved flow and pressure balance).

• Cost-effective for high-volume production.

❌ Disadvantages:

• High tooling cost (expensive to design, build, and maintain).

• ⚙️ Complex maintenance (electrical/heating systems involved).

• ⏱️ Longer lead time for mold manufacturing.

Suitable For:

• Mass production

• Multi-cavity molds

• High-performance materials

• Parts requiring cleaner finishes (less gate mark)

2. Cold Runner Mould

What is it?

A cold runner mold uses unheated channels to guide the molten plastic into the mold cavities. The runners cool and solidify along with the part and are ejected together.

Key Features:

• Runner system is not heated.

• Solid runner is formed and needs to be trimmed or recycled.

• Can be 2-plate or 3-plate molds.

✅ Advantages:

• Lower mold cost (simpler design and manufacturing).

• ️ Easier to maintain and repair.

• Suitable for lower production volumes or frequent material/color changes.

❌ Disadvantages:

• ❌ Material waste (runners must be trimmed and disposed of or reground).

• Longer cycle time (cooling time includes runner).

• ⚖️ Inconsistent quality in multi-cavity parts due to uneven flow.

Suitable For:

• Low to medium volume production

• Less complex or prototype molds

• Situations where material regrinding is acceptable

Quick Comparison Table:

If you want, I can also help you decide which runner system is better for your specific product. Just let me know the application of samples and your requirements, we can give you a better solution.