Die Preheat
Process Time = (Heating Time / Number of Dies) / Parts Per Die
Process time depends on the following:
• Heating time: see formula. This value is converted from hours to seconds for use in this formula.
• Number of dies: specified by the machine property Number of Dies.
• Parts per die: this is the number of parts produced by a die before it needs to be replaced. See formula.
Heating Time = Required Heat / Oven Power
Heating time in hours depends on the following:
• Required heat: see formula.
• Oven power: specified in kilowatts by the machine property Machine Power. This value is converted to watts for use in this formula.
Required Heat = (Billet Mass * Tool Material Specific Heat * Delta Temp)
Required heat depends on the following:
• Billet mass: this is the product of billet volume and material density. See
Billet Size and Parts per Billet.
• Tool material specific heat: specified by the Extrusion process tool shop variable Tool Material Specific Heat. This is the amount of heat energy per unit mass that is required to increase the temperature of the die material by one degree C.
• Delta temp: this is the magnitude of the temperature change effected by heating. See formula.
This value is converted from joules to watt-hours for use in the Heating Time formula.
Delta Temp = Solidus Temp – Room Temp
Delta temp is the magnitude of the temperature change effected by heating. It is the difference between the following:
• Solidus temp: specified by the part material property Solidus Temp. This is the highest temperature at which the part material remains entirely in a solid state.
• Room temp: this is the ambient temperature, specified by the cost model variable defaultRoomTemp (23°C in starting point VPEs).
Part per Die = Number of Billets per Die * Parts per Billet
The number of parts produced by a die (before it needs to be replaced) is the product of the following:
• Number of billets per die: this value is based on an evaluation of strain crack propagation. See the formula Number of Billets per Die in
Cycle Time.