A hot runner system is an assembly of heated components—hot halves, nozzles and gates and—that inject plastic into the cavities of an injection mold. The system usually includes a heated manifold and a number of heated nozzles. 

How to Optimize Pack & Hold Times for Hot-Runner & Valve-Gated Molds

Applying a scientific method to what is typically a trial-and-error process. Part 2 of 2.

Hot Runners: Essential Reading

Optimizing Pack & Hold Times for Hot-Runner & Valve-Gated Molds

Using scientific procedures will help you put an end to all that time-consuming trial and error. Part 1 of 2.

Hot Runners: A View from the Bottom Up

Addressing hot-runner benefits, improvements, and everyday issues from the perspective of decades of experience with probably every brand on the market. Part 1 of 2.

How to Detect and Prevent Hot-Runner Manifold Leaks

Minding the temperature gap at startup between the nozzle and manifold; visually and electronically monitoring signs for leaks; and preventive maintenance between runs can save you from hot-runner leak horror stories.

Molders’ Block: Dealing With Foreign Materials in a Hot-Runner System

Understanding plastic flow can help you understand how foreign materials move—or don’t move—through your hot-runner system.

A Planned Purging Program Can Boost Your Hot-Runner Efficiency

Molders can increase the efficiency of their hot-runner operations if a strategic approach is developed to address the need for required resin and color changes.


FAQ: Hot Runners


First, think of it as an extension of the molding machine itself. Its purpose is to keep the plastic molten at a proper temperature on its path to the cavity. So basically it’s just a piece of heated steel with a round channel in it for the melt to flow through. Ideally, this channel would be running at the exact temperature on the controller, free of obstacles such as dead spots or components that could create hangups and cause scrap issues with color changes or contamination. 



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