The Cooling Time in Injection Molding
Jun 02, 2020

The cooling time refers to the time required for the molten plastic inside the mold to cool and solidify, and accounts for 70% ~ 80% of the whole injection molding cycle time. The cooling time will directly affect the plastic product molding cycle time and output rate. The shorter is the molding time, the more parts would be able to produce with less time, and the lower overall costs.

Proper cooling time is benefit for the end quality of plastic parts. The temperature of the plastic products in the release stage should be cooled below to the temperature of the thermal deformation of the plastic products, in order to prevent the distortion caused by the residual stress and the external force. The biggest problem it may encounter with improper or insufficient injection molding cooling time is defective and rejected parts. The most common scenario will be parts that have not yet solidified enough to hold their shape, which are then damaged by the firing of the ejector pins. Improper or insufficient cooling, including poor mold design, can also result in excessive shrinkage, warpage and more defects in parts. Consistent, well-engineered cooling time is one of the biggest steps we can take to improving the quality of finished parts and reducing the number of defects. So there is a need of a cooling technique to reduce the cycle time without compromising on part quality.

The “Conventional Cooling Channels” are created by drilling several straight holes (cooling channels) inside the mold core and cavity. This kind of cooling process may take a longer time because of nonuniform cooling of part. Some studies have shown that the conformal cooling can reach a better result of cooling as compared to conventional cooling. Using the additive cooling lines with conformal cooling channels provides even more uniform cooling and takes less cooling time because not only these conform to the geometry of the part but also the additive lines improve the cooling.

There are many factors work on the cooling time, and then the cooling time plays a significant role on the injection molding. The optimum mold design should be proceed based on the molding conditions.

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