Challenges in Hot Runner Cleaning

Hot runners are widely used in injection molding to eliminate Sprue‑runner‑gate scrap, cut material‑costs, shorten cycle times, and improve product quality. However, they are expensive, and in multi-color production, the same mold is often used for different colors—leading to frequent color changeovers.

A key question: Can the same purging compound be used for both hot runners and screws? It is necessary to distinguish the raw‑material specifications of hot‑runners and injection screws. Hot runner components (sleeves, mandrels) that contact molten plastic are typically made of beryllium copper, Stellite, or nickel alloys, with hardness of HRC 34–45. Screws are generally nitrided or alloyed steel, with hardness of HRC 55–65. Hot runners are significantly softer.

In addition, hot runner flow channels involve splits and bends, making them more complex and harder to clean than barrels. When selecting a purging compound, manufacturers need thorough cleaning performance, but also worry about residue and potential damage to delicate hot runner components.

Our Solution: PlasE^® Series Purging Compounds

PlasE® purging compounds fit most hot‑runner systems. Formulas are customized to match the physical properties of mainstream plastics, minimizing risks of purge‑material carry‑over when switching resins. They are glass-fiber-free and will not scratch or wear hot runner surfaces. The compounds contain no halogens, heavy metals, PFAS, or other restricted substances, and are environmentally safe.

Through hot runner air-purge methods, PlasE^® material fully adsorbs residual resins in the runner system—including hard-to-reach areas—achieving thorough cleaning without disassembly.

Value Delivered

Almost all injection molding plants now use hot runners. Fast, reliable cleaning is a key competitive advantage.

Example:

A 1000T injection molding machine processing ABS, switching from black to white. 

- Previously: 150kg of regrind, ~5 hours cleaning time. 

- With PlasE® A2503 (air‑shot preceded purging‑moulding): ~15kg material, 1.2 hours cleaning time. 

Results: 

- Cleaning material reduced by **90%** 

- Cleaning time reduced by **75%** 

- With ~5 color changes per month, machine utilization increased by **~3%**

Additional Advantages

- Reduces material consumption, downtime, and labor costs 

- Improves overall equipment effectiveness (OEE) 

- Purges through molding, not air-shot—a capability most competitors lack 

- Meets environmental standards; selected grades are FDA-compliant, providing a safe solution for food-contact applications

Summary

PlasE® series purging compounds offer a fast, safe, and cost-effective solution for hot runner color changeovers—reducing waste, saving time, and protecting valuable tooling.