Shenzhen Alu Rapid Prototype Precision Co., Ltd.

A hot runner in injection molding is a heated system integrated into the mold that delivers molten plastic from the injection unit directly to the mold cavities, keeping the material at a consistent temperature throughout the flow path. 

It typically consists of a manifold (a heated distribution channel), nozzles, and gates, all maintained at elevated temperatures via electrical heaters to prevent the plastic from solidifying prematurely. 

How It Works

In a standard injection molding process, plastic pellets are melted and injected into the mold. A hot runner system:

1.Uses the manifold to branch the molten plastic to multiple cavities (for multi-cavity molds).

2.Employs insulated or externally heated runners to maintain fluidity, eliminating the need to re-melt frozen material.

3.Allows for precise control over temperature, pressure, and flow, often enabling valve-gated designs that open/close electronically for cleaner part ejection.

This contrasts with a cold runner system, where unheated channels cause the plastic to cool and solidify in the runners, requiring removal and recycling of that scrap material. 

Key Benefits

Reduced material waste: No solidified runners to discard, lowering costs (especially for expensive resins). 

Faster cycle times: Shorter cooling periods and easier ejection lead to higher production rates. 

Improved part quality: Consistent filling reduces defects like sink marks or flow lines, and enables complex geometries. 

Drawbacks: Higher upfront mold costs and more complex maintenance due to heating elements.