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Injection Molding Cooling Time Calculator

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Injection molding is a common process used in manufacturing to create complex plastic parts. The procedure involves melting plastic pellets, injecting them into a mold, and then cooling them until they solidify into the desired shape. One of the key elements in this process is cooling, as it significantly affects both the quality and productivity of the operation. To optimize this cooling period, the Injection Molding Cooling Time Calculator is an indispensable tool.

Understanding the Calculator’s Working

The Injection Molding Cooling Time Calculator employs a mathematical formula to compute the cooling time, which is the period required for the molten plastic in the mold to cool and solidify before it can be ejected safely and effectively.

The Formula and Variables

The formula used by the calculator is as follows:

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t = (h^2/(2pia)) * ln [ 4/pi * (Tm – Tmo) / (Teject – Tmo) ]


  • t is the cooling time. It’s the calculated outcome, the time required for the plastic to cool to the ejection temperature.
  • h is the part thickness. This parameter affects the cooling time as thicker parts require more time to cool.
  • a is the thermal diffusivity. This is the measure of how quickly heat transfers through the plastic material.
  • Tm is the melt temperature, which is the temperature at which the plastic pellets turn into a liquid state for injection into the mold.
  • Tmo is the mold temperature. This is the temperature of the mold before the molten plastic is injected into it.
  • Teject is the ejection temperature, the temperature at which the plastic must cool before it can be ejected from the mold without deforming.

A Detailed Example

For instance, let’s calculate the cooling time with the following parameters:

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Part Thickness (h): 4
Thermal Diffusivity (a): 3
Melt Temperature (Tm): 2
Mold Temperature (Tmo): 1
Eject Temperature (Teject): 55

By substituting these values into the formula, we get a cooling time of -3.1809104957507186. This is a theoretical calculation and may not align with the actual time due to various factors such as mold design, machine settings, and plastic material properties.

Applications of the Calculator

The Injection Molding Cooling Time Calculator is instrumental in many scenarios. It helps manufacturers to optimize the cooling phase of the injection molding process, resulting in improved efficiency and output. Additionally, it can be used to model different scenarios, helping engineers make data-driven decisions about material selection, mold design, and process parameters.

Most Common FAQs

Why is accurate calculation of cooling time important in injection molding?

Precise calculation of cooling time can increase efficiency, reduce cycle time, and enhance the quality of the molded parts. It also helps in predicting and preventing potential defects.


The Injection Molding Cooling Time Calculator is a powerful tool for anyone involved in the injection molding process. By understanding its working, the formula it uses, and its application, users can effectively optimize their processes, improving quality, reducing cycle times, and ultimately boosting profitability. To achieve best results, it’s essential to consider the limitations and understand that actual times can vary based on factors not included in the formula. As such, it is always recommended to use the calculator as a guideline and validate the results with actual molding trials.

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