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Why is Core Preload Important for Injection Molds?

Why is Core Preload Important for Injection Molds?

Although most manufacturers do not think about it, core preload is an important part of any successful injection molding project that requires not only precision but uniformity. As the creator of KOR-LOK® Side Action Systems, PFA understands not only core forces under injection but also how preload is necessary to overcome those forces and the importance of choosing a locking cylinder that can maintain preload even at zero PSI. But what exactly is core preload and what role does it play in the successful completion of an injection molding process? 

During the injection molding process, cores are placed under intense pressure and thermal variation that will often cause the core length to decrease or distance from the desired position that was set initially. Often these changes can be seen on the completed part as if the entire core had “backed up” as much as .020” or more depending on the geometry of the mold that was used. With core preload, these changes can be eliminated, and the product will retain the exact shape with no backup variation seen on the completed part. This is due to the ability to maintain core preload at a rated load even when no hydraulic pressure is being applied. 

Simply put, achieving core preload means that your parts can be made with perfect match lines, tighter tolerances and clean textures. Together, these unique characteristics make the creation of complex parts through injection molding much easier and eliminates scrap while ensuring faster and easier builds. When core preload is achieved for injection molds with KOR-LOK®, manufacturers also can eliminate flash on complicated parts because the cores can move at any angle at any time to remove barriers that could be causing issues to occur. 


How Can KOR-LOK® Improve Injection Molds? 

What makes the KOR-LOK® Side Action System different from other hydraulic core pull and locking cylinders available to manufacturers is its ability to preload cores at incredibly high forces. Unlike spring-locking, hydraulic-activated locking cylinders and other piston-locking cylinders, KOR-LOK® can achieve preload to the rated load and can continue to maintain that preload even at zero PSI. And, while PFA makes other locking cylinders for general industrial use, only the KOR-LOK® achieves high force preload and cylinder locking to full rated load in a simpletoinstall system. 

Once set using only a minimum of 1,500 psi hydraulics, KOR-LOK® Side-Action Systems provide 100% preload to rated load – 10 times more force than a standard cylinder. KOR-LOK® does not just lock, it “super locks” by preloading and locking in the force so hydraulics are no longer needed. The result is 100% preload to rated load at zero pressure. This is a feat that may not be achievable with other setups or injection molding systems that are designed to manufacture complex parts quickly and accurately without the risk of creating scrap or excessive amounts of flash. If you are interested in learning how KOR-LOK® can improve your injection molding processes, we would love to talk! 

Plastic & Injection Molding