Cold runner and hot runner are two different types of molding systems can be used in the injection molding process. The both systems have their advantages and disadvantages. Understanding the key difference will help you decide which process is best for your project.
What is the Cold Runner System
Cold runner system for injection molding consists of two to three plates within the mold. The system injects the plastic into the mold through the sprue and feeds the runners, which lead to the parts in the mold cavity. The part and the runner are joined in two plate system, which requires An ejection method to remove the both. In three plate system only the parts is ejected separately, as the runner is placed on a different plate.
Simple mould design
Cheaper to produce & easy to operate
Quick to modify colors
Suitable for a wide variety of polymers
Take longer in production
Require to remove the runners during the process
Creates waste if the runners cannot be recycled
What is the Hot Runner System
Hot runner molds consist of 2 plates that are heated by a manifold system. There are two types of hot runner systems, externally heated and internally heated.
Externally heated moulds are better for materials that are sensitive to heat, while internally heated moulds provide better flow control. The hot runner system ensures that the plastic remains molten throughout the entire runner process until the mould cavity.
Faster cycle times
Higher quality parts
Can accommodate geometrical parts
Higher costs for equipment and maintenance
Color cannot be changed easily
May not be suitable for thermally sensitive polymers
In order to choose the best injection molding system fit your project, there are many factors to consider. The hot runner system, you can maximise manufacturing productivity with faster cycle times, reduce wasted plastic during high volume shoots because the channel is smaller so less plastic needs to be shot during each cycle, but is a more expensive system. The cold runner molds, on the other hand, could make color changes easily,less expensive and easier to maintain,but can create waste.
When choosing between cold runner molds or hot runner molds to make your plastic parts, consult with an experienced professional who can help you determine which method is right for you. You will need to consider cost and the type of material with which you are working, and a knowledgeable injection molder can educate you about your options.