Heat transfer potential using water cooling channels in a mold is affected by several factors:
Our calculator can help determine the size and total length of cooling channels needed in a mold to ensure adequate cooling capacity with a given water temperature. These calculations are based on the heat that must be removed to cool the molded part from processing temperature to a safe ejection temperature. With this information designers can estimate sizes and quantity of cooling circuits needed to provide adequate cooling. The calculator can also help processors evaluate the adequacy of cooling designs in existing tooling.
Your cooling system may not be capable of cooling at the rate you need. Potential cooling rate is determined by entering Molding Variables and Cooling Parameters into the calculator. Factors such as scale or biological deposits inside the cooling channels can decrease the heat transfer rate, increase pressure drop, and prevent reaching the full cooling potential.° Also, the size and length of your cooling circuits may not be adequate.° These conditions of course will result in longer than optimum cycle times.
Engineering solutions always involve compromises and mold cooling designs are no exception. Surprisingly, warmer water improves heat transfer slightly due to its lower viscosity, but as water and mold temperature increase, the temperature difference between melt and mold surface decreases, thus reducing heat transfer. A balance must be struck between these competing factors.° Another interesting fact is that smaller diameter cooling channels yield a higher heat transfer rate for a given flow than larger passages. The tradeoff is that smaller passages create more pressure drop and therefore require more pumping horsepower.°
Footnote: We offer this Mold Cooling Calculator tool as a free service to the injection molding industry. While some molds or inserts have simple, straightforward cooling circuits, many have multiple circuits of various sizes and configurations. In these cases each circuit might remove a different percentage of the heat input. Users must therefore employ this tool with awareness and judgment. Trying out different molding and cooling variables is simple and quick. In complex cooling schemes one can easily analyze each cooling circuit separately and combine the results. We are eager to learn how you have used the calculator and to hear your constructive feedback so we can enhance and improve the utility of the Smartflow Mold Cooling Calculator.