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Cooling Time For Moulding Calculator

Work out cooling time for moulding instantly with clear inputs, formula shown and shareable results.

About Cooling Time For Moulding Calculator

Cooling time follows one-dimensional transient conduction through the wall: t = h² / (pi² alpha) x ln[(4/pi)(Tmelt - Tmould) / (Teject - Tmould)], with thermal diffusivity alpha around 0.09 mm²/s for common polyolefins. Because thickness is squared, cooling dominates the cycle and a small reduction in wall thickness pays back far more than colder water.

Formula

Cooling time

t = h² / (pi² x alpha) x ln[(4/pi) x (Tmelt - Tmould) / (Teject - Tmould)]

h
Wall thickness
alpha
Thermal diffusivity

Worked example

With the default values below, Cooling Time For Moulding Calculator returns Cooling time of 11.09. Change any input above and every figure here is recalculated in your browser.

Inputs used

Maximum wall thicknessminimum 0.1 mm
2.5 mm
Melt temperatureminimum 50 °C
230 °C
Mould wall temperatureminimum 5 °C
40 °C
Ejection temperatureminimum 10 °C
90 °C

Results

Cooling time
11.09 s
Estimated cycle time
17.7 s
Temperature ratio
3.8000
Cooling time per mm² of thickness
1.775 s/mm²

Step by step

  1. 1Values used
  2. 2Cooling time
  3. 3Cooling time= 11.09 s
  4. 4Estimated cycle time= 17.7 s
  5. 5Temperature ratio= 3.8000
  6. 6Cooling time per mm² of thickness= 1.775 s/mm²

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Cooling Time For Moulding figure worked out?

t = h² / (pi² x alpha) x ln[(4/pi) x (Tmelt - Tmould) / (Teject - Tmould)]. Cooling time follows one-dimensional transient conduction through the wall: t = h² / (pi² alpha) x ln[(4/pi)(Tmelt - Tmould) / (Teject - Tmould)], with thermal diffusivity alpha around 0.09 mm²/s for common polyolefins.

Why is cooling most of the cycle?

Injection and packing take a second or two, but heat has to conduct out through the wall, and that time grows with the square of thickness. Thick sections are the usual reason a cycle is long.

What values do I need to enter?

This calculator takes 4 inputs: Maximum wall thickness, Melt temperature, Mould wall temperature, Ejection temperature. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.

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