Cool Formulas

The sand casting subprocess Cool relies on the formulas below.

Cycle Time = Process Time * Cycle Time Adjustment Factor

Cycle time is the product of the following:

• Process time (see formula below)

• Cycle time adjustment factor: specified by the cost model variable cycleTimeAdjustmentFactor; 1 in aPriori starting point VPEs.

Process Time = Mold Constant * (Part Volume / Part Surface Area)^2

Process time is calculated using Chvorinov’s rule for cooling. It is a function of the following:

• Mold constant (see formula below)

• Part volume (obtained from GCD extraction)

• Part surface area (obtained from GCD extraction)

Mold Constant = ( (Metal Density * Heat of Fusion) / (Pour Temperature – Mold Temperature) )^2 *

( Pi / (4 * Thermal Conductivity of Mold * Mold Density * Specific Heat of Mold) ) *

( 1 + ((Specific Heat of Metal * (Pour Temperature – Ejection Temperature) / Heat of Fusion)^2) )

The mold constant depends on properties of the mold and part material, and is independent of part size. The constant is a function of the following:

• Metal density. Specified by the material property Density.

• Heat of fusion. Latent heat of fusion of the material. Specified by the material property Heat of Fusion.

• Pour temperature. Pour temperature of the material. Specified by the material property Injection Temp.

• Melting temperature. Melting or freezing temperature of the material. Specified by the material property Liquidus Temp.

• Mold Temperature. Initial temperature of the mold. Specified by the cost model variable sandMoldTemp (assumed to be room temperature in starting point VPEs).

• Thermal conductivity of mold. Specified by the cost model variable sandMoldThermalConductivity (0.5 Watts per meter per degree Kelvin in starting point VPEs).

• Mold density. Specified by the cost model variable sandMoldDensity (1600 kg/m3 in starting point VPEs).

• Specific heat of mold. Specified by the cost model variable sandMoldSpecificHeat (1170 Joules per kilogram per degree Kelvin in starting point VPEs).

• Specific heat of metal. Specified by the material property Specific Heat.