Cooling Time Calculator
Calculate the optimal cooling time for an injection molded part based on wall thickness, melt temperature, and mold parameters. The calculator uses the Ballman-Shushman equation — an analytical method for estimating cooling time for one-dimensional heat flow through a flat wall.
Input Parameters
Results
Fill in the data and click Calculate
In ARGUS, cooling time is automatically linked to cycle time and costs
One click instead of 5 calculators — ARGUS combines thermal calculations with the full project context: material, machine, and production history.
How do we calculate cooling time?
The cooling time of an injection molded part is the time required for the polymer in the mold to reach a safe ejection temperature — the temperature at which the part is sufficiently rigid not to deform under the ejectors and its own weight. In practice, cooling time accounts for 50–80% of the total injection cycle time, making it the key parameter of production economics.
The calculator uses the Ballman-Shushman equation — an analytical solution to Fourier's heat conduction equation for one-dimensional heat flow through a flat wall. The model assumes symmetric cooling of both sides of the part and uniform thermal properties of the material.
s — wall thickness [mm]
α — thermal diffusivity [mm²/s]
Tm — melt temperature [°C]
Tw — mold temperature (cavity wall) [°C]
Te — ejection temperature [°C]
Thermal diffusivity α describes a material's ability to conduct heat relative to its ability to store thermal energy. It is defined as α = λ / (ρ × cp), where λ is thermal conductivity, ρ is density, and cp is specific heat. For typical thermoplastics, α ranges from 0.07 to 0.20 mm²/s.
Cooling time for common materials
The values below refer to a part with a 2.5 mm wall thickness at typical processing conditions. Actual cooling time depends on part geometry, cooling system efficiency, and mold specifics.
PP — 10–16 s (α ≈ 0.09 mm²/s)
PA6 — 12–18 s (α ≈ 0.10 mm²/s)
PC — 10–15 s (α ≈ 0.11 mm²/s)
POM — 12–20 s (α ≈ 0.09 mm²/s)
HDPE — 14–22 s (α ≈ 0.08 mm²/s)
PET — 8–14 s (α ≈ 0.11 mm²/s)
Cooling time increases proportionally to the square of wall thickness — a 5 mm thick part cools 4× longer than a 2.5 mm part under identical thermal conditions. This fundamental relationship determines both cycle time and production economics.
Mold temperature has a dual effect on part quality: a lower temperature shortens cooling time but can degrade surface quality and increase internal stresses. For semi-crystalline materials (PP, PA, POM), excessively rapid cooling limits crystallization, affecting mechanical properties and dimensional stability.
When to use with caution
The Ballman-Shushman equation gives a good approximation for parts with uniform wall thickness and symmetric cooling. For parts with large thickness variations, heavy ribbing, or thick gates, the actual cooling time may be 15–30% longer than the calculated value.
The model does not account for: cooling asymmetry (different temperatures on each mold side), crystallization heat of semi-crystalline materials, shear heating effects during injection, or the influence of holding pressure on heat transfer conditions. In the ARGUS system, cooling time is determined taking into account full part geometry, production history on the specific machine, and material data from the plant database.
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