Cooling Time Calculation Tool

Calculation of temperature profiles and cooling times in injection molding

When selecting a suitable material, being able to compare the required cooling time can play an important economic role in the decision making process. An auxiliary program of Material Data Center links the extensive plastics material database with the solution of one of the most common heat transfer problems. The solution of what is known as the one-dimensional heat equation, or diffusion equation, is specifically applicable to the type of heat transfer that occurs within the injection molding process. The problem is solved using a finite difference approach. Although this calculation only takes a second or two to compute, the real power of this auxiliary program is that it is closely connected with the materials in Material Data Center. With the click of the mouse, the program calculates the cooling time and displays both the average and through-thickness temperature profiles for a given material and part thickness.

To make this evaluation process as flexible as possible, the user has the freedom to modify or enter the needed parameters for a calculation.

 

The following assumptions are made in the calculation of the cooling time:

  • It is assumed that any in-plane heat transfer that occurs is negligible. That is to say, that the heat transfer occurs mainly in the part through-thickness direction. This allows the problem to be reduced to one dimension.
  • The thermal material properties are taken from the melt and are assumed to remain constant throughout the cooling process (do not change with temperature).
  • The influence of pressure is not taken into account.
  • A uniform melt temperature is assumed at the beginning of the calculation.
  • The wall temperatures are assumed to be the same on both sides of the part and are assumed to remain constant throughout the process.
  • There is no heat transfer resistance assumed between the material and the wall.
  • The cycle time is calculated from the start of the cycle (injection of the melt) until the average material temperature is below the specified ejection temperature.

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