Calculate optimal cooling time for injection molded parts based on material properties and wall thickness.
Enter part and process specifications
Calculated cooling time and temperature sensitivity
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The formula, inputs and assumptions behind the estimate above.
t = h² / (π² · α) × ln( (4 / π) × (Tmelt − Tcoolant) / (Teject − Tcoolant) )
This is the first term of the series solution for one-dimensional transient heat conduction in a flat plate. It gives the time for the hottest point, at the mid-plane of the thickest wall, to fall from the melt temperature to the ejection temperature while both mold faces are held at the coolant temperature. The 4 / π factor is the mid-plane coefficient of that first term. The calculator evaluates the expression exactly as written, with π² taken as 9.8696.
| Symbol | Meaning | Unit | Source in the calculator |
|---|---|---|---|
| t | Required cooling time for the wall mid-plane to reach the ejection temperature | s | Calculated result, shown as Required Cooling Time |
| h | Maximum wall thickness, the thickest section of the part | mm | Maximum Wall Thickness field (0.1 to 50 mm) |
| α | Thermal diffusivity of the selected polymer family | mm²/s | Built-in value for the selected Material (see below) |
| Tmelt | Material temperature at injection | °C | Melt Temperature field (150 to 400 °C) |
| Teject | Part temperature at ejection, at the wall mid-plane | °C | Ejection Temperature field (40 to 200 °C) |
| Tcoolant | Temperature of the cooling medium, taken as the mold wall temperature | °C | Coolant Temperature field (5 to 95 °C) |
The calculator uses one fixed value per polymer family. These are generic reference values, not grade-specific data.
Using the calculator defaults: ABS, h = 2.5 mm, melt 230 °C, ejection 80 °C, coolant 25 °C, with α = 0.08 mm²/s for ABS.
The Temperature Sensitivity chart repeats the same calculation for ejection temperatures from 20 °C below to 20 °C above the entered value in 5 °C steps. For this example it runs from 15.9 s at 60 °C to 9.9 s at 100 °C. Because t scales with h², increasing the wall to 3.0 mm raises the estimate to 17.8 s.