Hot runner molding systems #1

Introduction and advantages

Eastman receives many questions about molding Eastman Tritan^™ copolyester with hot runner systems. It can be a complex topic, loaded with variables that include not only mold design, but also part size, polymer formulation, and part design. Success depends on early collaboration and clear communication between Eastman, molders, tool builders, and hot runner suppliers.
 
We’re usingTritanMoldIt.com as a platform to jumpstart this communication between stakeholders.  During the next few months, the Tritan experts will post a series of blogs, beginning with this overview and advantages of hot runners for amorphous copolyesters, including Tritan. 

We invite you to help shape our series of hot runner blogs. Send your feedback. Ask your questions. Share your success stories. We look forward to hearing from you.
 

Key advantages of hot runner systems

In a hot runner molding system, the runners are within the mold. They are heated to maintain the plastic resin in a liquid state (a temperature above the material’s softening temperature, Tg) within the tool until it passes through the gate into the mold cavity. Unlike a cold runner system, hot runners are not ejected with the finished part. Instead, they stay in the mold in a liquid state, ready to fill the cavity on the next shot.
 
Hot runner systems are popular for high-production runs or in high-cavity molds, where quality is critical and gate witnesses are objectionable. A hot runner system can offer these advantages:
• Less resin used because there is virtually no waste
• Shorter flow path
• Reduced injection time; reduced open-dwelling time
• Lower cost per part for high-volume production—especially small parts
• Higher part quality
• More design flexibility

In Part 2 of our hot runner series, we’ll start focusing on specific ways for getting the best results with Tritan in a hot runner system.