PRODUCT OVERVIEW ② CARTRIDGE HEATER SOAKING TYPE
② Calculate number of heaters and wattage for one heater. Decide the number of the heaters depending on the size of heated object, and get total wattage (W) required to rise the temperature of the heated object. Example) Use six heaters of 1000 (W) (Total 6000W) ＊ The above calculation method does not concern heat loss. Please consider approximately 20–30% increase for the calculated value in kW. ■ Selection of soaking cartridge heater ① Determine the heater diameter (D), length (L), voltage (V) and the total wattage of the heater (W) in the same way as for a conventional cartridge heater.
■ Characteristics The heater wattage of a soaking type cartridge heater is divided and set into three zones according to the shape and size of the object being heated, and also the amount of heat dissipated, resulting in a more uniform heat distribution than that of a general cartridge heater.
This type is suitable for when the temperature of a general cartridge fails to stabilize, and the molded product is warped, its dimensions vary randomly, problems related to luster occur, or when more accurate die temperature distribution control is required such as when molding liquid silicone rubber (LSR) or thermosetting resin.
L
(Example) MKCHA12–300–V220–W1000 (D) (L) (V) (W)
■ Basic Structure Drawing
V (Voltage)
W (Total wattage)
② Determine the wattage rate of the tip (X) and the wattage rate of the root (Y) for the case where the wattage rate of the center is the reference value of 1. ＊ Because the center is defined as the reference value of 1, there is no need to specify it. (Example) MKCHA12–300–V220–W1000–X1.4–Y1.6 (D) (L) (V) (W) (X) (Y) (Following example of wattage rate: When X and Y are specified based on reference values of a one–sided horizontal insertion die.)
Length of heater body (L) Length of heat generation section (HL)
• Wattage rate This means the distribution ratio with respect to the total wattage of the entire heater (W). It is possible to specify the wattage rates of the tip and root as multiples with respect to the wattage of the center as the reference value of 1. X = Wattage rate of tip 1 (Reference value) = Wattage rate of center Y = Wattage rate of root A + B = Length of non–heat generating section
A
B
Tip (HL/3)
Center (HL/3)
Root (HL/3)
3 HL
3 HL
3 HL
3 HL
3 HL
3 HL
X
Y
1 (Reference value)
1 1.6 1.4 （ X ） （ Y ） (Reference value 1)
350W 250W 400W （ X ） （ Y ） (Reference value 1)
Total 1000W
Wattage rate
Wattage of each part
Wattage rate
The wattage of each part is calculated by using the “wattage calculation equation”.
• W density (W/cm 2 ) Limit equation When the wattage density becomes 15 (W/cm 2 ) or more, wire breakage is liable to occur, so specify the W density of each part within the range 2–15 (W/cm 2 ).
Isotherm distribution for the case where a cartridge heater soaking type is installed on the mold (outline drawing)
Isotherm distribution for the case where a cartridge heater soaking type is installed on the cavity die (outline drawing)
High temperature area
Low temperature area
Cavity
Mold
• Wattage calculation equation of each part
Guide pin
X (Wattage rate of tip)
Wattage of tip
Wattage of tip = W (Total wattage) ×
Wattage density of tip (W/cm 2 ) =
Isotherm
HL 3 × D × 3.14 ÷ 100
X + Y + 1 (Total wattage rate)
High temperature area Low temperature area
Cavity
Isotherm
1 (Wattage rate of center) X + Y + 1 (Total wattage rate)
Wattage of center HL 3 × D × 3.14 ÷ 100
Wattage of center = W (Total wattage) ×
Wattage density of center (W/cm 2 ) =
Cartridge heater soaking type
Mold
Core
Y (Wattage rate of root)
Wattage of root
Wattage of root ＝ W (Total wattage) ×
Wattage density of root (W/cm 2 ) =
HL 3 × D × 3.14 ÷ 100
X + Y + 1 (Total wattage rate)
■ Example of wattage rate (reference value)
Sprue (high temperature area)
Low temperature area
High temperature area
Top
One-sided horizontal insertion die
Double side horizontal insertion die
Vertical insertion die
Yellow
Red
3 HL
3 HL
3 HL
3 HL
3 HL
3 HL
3 HL
3 HL
3 HL
Low temperature
High temperature
Cartridge heater soaking type
Wattage rate Heater surface temperature Work piece surface temperature
Wattage rate Heater surface temperature Work piece surface temperature
1.4
1
1.6
1.6
1 1
1 1
1.6
■ Installation method and precautions for use It is possible to install this type in the same way as an ordinary cartridge heater. For the method of installation and precautions for use, refer to Outline of Cartridge Heater ( P.1049 ). ■ Selection method ① Calculate the necessary wattage (kW) for the heater. It is calculated from the mass of the object to be heated, the specific heat, increase in temperature, and the time required to heat to the set temperature by the following formula. Weight of heated object (kg) × Specific heat of heated object (kcal/kg∙°C) × Temperature increase (°C) 860 × Heating time (h) × Efficiency ( η ) Though it is difficult to calculate efficiency ( η ) accurately because it varies on conditions of heat–retention heat insulation, arrangement of the heater, and etc. generally 0.2–0.5 is suitable. Example) Necessary wattage (temperature 21°C) when controlling stainless mold of 130kg with heater and raising mold temperature up to 110°C in 30 minutes Necessary wattage for heater (kW) =
地
MKCHA12 － 200 － V200 － W300 － X1.4 － Y1.6 （ W （ ） V （ ） L （ ） D ） （ Y （ ） X ）
MKCHA12 － 200 － V200 － W300 － X1 － Y1.6 （ W （ ） V （ ） L （ ） D ） （ Y （ ） X ）
Ordering example)
Ordering example)
MKCHA12 － 200 － V200 － W300 － X1.6 － Y1.4 （ W （ ） V （ ） L （ ） D ） （ Y （ ） X ）
Ordering example)
• Specific gravity/Specific heat of main materials Material Specific gravity (g/cm 3 ) Specific heat (kcal/kg∙°C) Aluminum (A7075P series) 2.80 0.230 Steel 7.85 0.113 Stainless Steel 7.82 0.110 Brass 8.70 0.100
＊ In the above wattage rate example, the wattage rate, heater surface temperature and surface temperature of the work piece are reference values. The temperature distribution of the heated work piece varies with the characteristics of the work piece (shape, size, material, heat dissipation), heater distribution and various other conditions, so the actual value will be different from the above.
130 [kg] × 0.11 [kcal/kg∙°C] × (110−21)[°C] 860 × 0.5 [h] × 0.5 [ η ]
Necessary amount of heat for the heater (kW) =
1051
1052
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