When heating metal modules, plastic molds, or hot runners with a high-power mold cartridge heater, we usually insert it into a machined hole. However, the outer diameter of the cartridge heater and the clearance between the mounting holes have a direct impact on the service life of the cartridge heater.The gap is too big, the mold cartridge heater cooling effect is poor, the life is short; the gap is too small, the mold cartridge heater replacement is very difficult, encounter such a problem, what should wedo?
These lection of mounting hole size of cartridge heater is closely related to the heat density of heater. The temperature produced by different heat densities is different, and the expansion degree of casing is also different. Therefore, it is necessary to combine the relationship between the two to make a suitable mounting hole size.
Firstly, we determine the operating temperature of the heated object. Secondly, we select the heater suitable for size and power, and calculate its thermal density.
Thirdly, combined with the heat density and the temperature curve, we find the corresponding gap parameters.
Finally, according to the data found, choose the intermediate value to determine the final data.
(Example)Choose a 10 mm diameter mold cartridge heater, the size of the heater is 9.93 + 0.03 mm, we choose 10 m + 0.02 mm installation aperture, mold temperature 300 degrees, the maximum heat density of the electric heat pipe? What is the maximum power of an electric heating tube with a length of 200mm?
(1)By calculating the known data, we can get that the maximum gap between the installation hole and the electric heat pipe is 10.02-9.90=0.12mm. From the data point of view, the maximum heat density of the corresponding heater is 25W/cm2.
(2)According to the parameters mentioned above, the effective heating length of the 200 mm electric heat pipe can be calculated as 180 mm, and the maximum density is 25W/cm2. The maximum power can be obtained by the following formula: electric heat pipe power = thermal density *heating length * electric heat pipe diameter * 3.1416 = 25 * 18 * 3.1416= 1413W.
Points for attention in design of die cartridge heater
For the mold cartridge heater, the most important thing is to ensure that the heat generated by the heating rod can be transferred to the heating medium in time, reducing the temperature of the material inside the heating rod, so as to effectively improve the service life of the mold cartridge heater.
(1)The gap between the outer diameter of cartridge heater and its insertion aperture should be reduced as far as possible. Usually the gap between them is less than 0.1 mm. For example, the heating rod with 10diameter should be the aperture with 10.1 diameter.
(2)When machining mounting holes, the coaxiality and tolerance should be effectively guaranteed, such as using reamers and other tools to dress the machining.
(3)The mold cartridge heater should be installed before cleaning the residue left in the processing, such as organic oil and other residues, after heating will be carbonized, thus affecting the ability of heat conduction.
(4)There will be no problem in the use of the design voltage, the actual power can be calculated according to the following formula:
[use voltage / design voltage] * [use voltage / design voltage] * design power = power used.
An electric heat pipe with a rated voltage and power of 230V 500W and a voltage of 220V has a power of 418.6W, about 84% of the rated power.