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SANKO GOSEI

Mold Temperature Control and Theoretical Equations

Mold temperature control is used to control the appearance of the molded product, prevent warpage, maintain the mechanical properties of the material, and shorten the molding cycle.

and to shorten the molding cycle time.


              Figure 1 Temperature gradient of mold

(1) Temperature gradient

 Figure 1 shows the temperature gradient of the mold. (a) is the case of water circulating at 59.83° in a large channel.

 (a) shows a temperature gradient of 60-60.05°C at the surface of the cavity. 

 On the other hand, in case (b), when water of 45°C is circulated in the waterway, a temperature change of 53.33°C to 60°C is observed on the surface of the cavity.

 temperature change of 53.33°C to 60°C even if water of 45°C is circulated. This is not appropriate as a temperature distribution.


(2) Calculation of heat transfer area

 Q: Heat transferred (kcal/hr) To: Temperature at which the molded product is removed (°C) 

 hω: Border film heat transfer coefficient of cooling groove (kcal/m2hr°C) d: Diameter of cooling hole (m)

u: Flow velocity (m/sec) ρ: Density (kg/m3) ΔT: Average temperature difference of the cold (heat) medium in the mold (°C)

 t1: Melting temperature of molding material (°C) Cp: Specific heat of molding material (kcal/kg°C)

 Sh: Shots per hour (-) µ: Viscosity (kg/m,sec) λ: Thermal conductivity of refrigerant (kcal/m.hr.°C)

 A: Heat transfer area of the mold (m2), then


Q=Sh・Cp・(t1-t0) hω=λ/d(d・u・ρµ)^0.8×(Cp・µ/λ)^0.3 and

The required heat transfer area is A=Q/hW/ΔT.


(3) In case of temperature control by heater

 w: Required heat capacity (KW) Cp: Specific heat (0.115) (kcal/kg°C) G: Mold weight (kg) T1: Required temperature (°C)

 T2: Atmospheric temperature (°C) H: Rise time (hr) η: Efficiency (0.2-0.5)


W=Cp・G・(T1-T2)/(860・H・η)

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