The main function of the mold temperature machine is to control the temperature of the mold. Before that, Dongguan Guansheng Machinery Co., Ltd. also introduced some related knowledge of the mold temperature machine , such as the application of the mold temperature machine in the die casting process, and the mold temperature. Machine cooling system basics, etc., this article mainly explains the correct way to buy a mold temperature machine, which includes three major knowledge modules, which are considered when selecting the appropriate mold temperature controller and mold temperature controller. The factors and the method of learning to calculate are as follows:
First, select the appropriate mold temperature controller:
Random purchase of mold temperature control products DC high-voltage generator can bring 20% profit loss at any time, so we must carefully consider the production needs when purchasing, strictly verify the capabilities of the mold temperature controller before making a decision. Unfortunately, people often overlook this extremely important part of injection molding technology, and often wake up when there are problems with productivity and quality.
2. When selecting a mold temperature controller, the following points are the main considerations;
1. Pump size and capacity.
2. Internal throat dimensions.
3． Heating capacity.
4． Cooling capacity.
5． Form of control.
3. Learn to calculate:
A, the size of the pump:
From the known heat dissipation required per cycle, we can easily calculate the required volume flow rate of the coolant, and then obtain the correct cooling capacity required. The manufacturer of the mold temperature controller DC high voltage generator
Most provide formulas for calculating the lowest pump flow rate. Table 4.1 is useful when choosing a pump, it accurately lists the heat dissipation capabilities of different plastics. The following decides the experience that the pump needs to provide the minimum flow rate
Rule: If the temperature difference across the cavity surface is 5 ℃, the temperature difference is 0.75 gal / min / kW @ 5 ℃ or the temperature difference is 151 / min / kW @ 5 ℃. If the temperature difference across the cavity surface is
At 1 ° C, the required minimum flow rate needs to be multiplied by five times, which is 3.75 gal / min / kW or 17.031 / min / kW. In order to obtain product quality stability, many injection molding companies should
The temperature difference on the cavity surface is controlled at 1-2 ° C, but in fact many of the injection molding manufacturers may not know the importance of this temperature difference or think that the optimal range of the temperature difference is 5-8 ° C. Calculate coolant
The required volume flow rate should use the following procedure:
1. First calculate the heat to be removed from the city where a plastic / mold combination is planted: If the aforementioned PC cup mold is used as an example, the actual heat to be dissipated is:
Gross weight of one module (g) / cooling time (s) = 208/12 = 17.333 g / s
PC heat dissipation rate = 368J / g or 368kJ / kg
So the heat to be dissipated per cycle = 368 x 17.33 / 1,000 = 6.377 kW.
2. Then calculate the volume flow rate required for cooling: According to the above rule of thumb, if the temperature difference on the cavity surface is 5 ° C,
Flow rate = 6.377 × 0.75 = 4.78 gal / min or = 6.377 × 3.41 = 21.751 / min If the temperature difference in the mold cavity is 1 ° C, the flow rate = 4.78 × 5 = 23.9 gal / min or = 21.75 × 5 = 108.731 / min .
3． Regulation of pump flow rate: In order to obtain a good heat dissipation effect, the flow capacity of the pump should be at least 10% greater than the calculated result, so a pump of 27 gal / min or 120 / min is required.
4． Regulation of pump pressure: The operating pressure of the general mold temperature controller is 2-5 bar (29-72.5 psi). Because the pressure is insufficient, it will affect the volume flow rate of the cooling liquid (
The resistance of the flow causes pressure loss), so the higher the pump pressure, the more stable the flow rate. For molds with very small cooling pipes (for example, the pipe diameter is 6mm / 0.236in), the pressure of the pump needs to have
10 bar (145 psi) can provide sufficient heat dissipation speed (ie, the coolant speed). In general, the higher the volumetric liquid velocity of the coolant is, the smaller the diameter of the pipeline is, the greater the required pump output pressure is.
Therefore, the pressure of the mold temperature controller should exceed 3 bar (43.5 psi) in general applications.
B. Heating capacity:
1. The heating capacity required to raise a 500 kg mold to 50 ° C is 3 kWhr.
2. The additional heat capacity required to raise a 700 kg mold to 65 ° C is 6.5 kW / hr. In general, the stronger the heating capacity, the shorter the heating time required (the heating capacity is doubled,
Decrease in warming time). Provides a very useful information for injection molding manufacturers, you can immediately find out the heating requirements of any mold, so as to obtain the correct heating capacity of the mold temperature controller. Often because
The capability of the mold temperature controller is too low, resulting in the mold cannot reach the optimal temperature state. To know the actual performance of the mold temperature controller, we can compare its actual and calculated mold temperature rise time.
C. Freezing capacity:
The design of the refrigerating circuit of the mold temperature controller and its components are important to the precise control of the mold temperature. When the temperature of the mold or the heating liquid rises to the set value, the mold temperature controller must be able to quickly and effectively
Effectively avoid the temperature to continue to rise, the method is to introduce another lower temperature liquid, the introduction of the control of the solenoid valve. So the elimination and stability of temperature override depends on the size of the solenoid valve.
The aperture of the cooling solenoid valve can be calculated by the following formula: Inlet pump Valve freezing capacity (gal / min) = kW × 3.16 / △ t
Here △ t = the difference between the production temperature and the frozen water temperature set by the mold temperature controller:
kW = Heat to be removed by the mold
The following table lists the volumetric flow rates that can be provided by different solenoid valve apertures:
Solenoid valve aperture
in mm gal / min 1 / min
0.25 6.35 0.7 3.18
0.375 9.53 1.2 5.45
0.500 12.70 3.3 14.98
0.750 19.65 5.4 24.52
1.000 25.40 10.0 45.40
1.250 31.75 13.0 59.02
1.500 38.10 20.0 90.80
After calculating the refrigeration capacity, you can find the corresponding solenoid valve from the above table, as the following example:
The heat that PC cup mold needs to remove is 6.377kW
Production set temperature is 90 ° C
The temperature of frozen water is 18 ℃
△ T = 90－18 = 72 ℃
So freezing capacity = 6.377 × 316/72 = 0.28gal / min or 1.271 / min
It can be known from the above table that the solenoid valve with a hole diameter of 6.35mm / 0.250in can provide sufficient volume flow rate, which is suitable for the precise requirements of the mold temperature control range of ± 1 ° C. Pressure drop of solenoid valve
Ringing flow. The flow rate values in the table above are based on a pressure drop of 1 bar (14.5 psi). So the higher the pressure drop, the faster the chilled water will flow. A typical pressure drop for a solenoid valve is 2 bar (29 psi).
D. Liquid mold temperature heating control system:
The main purpose of any mold temperature controller is to control the mold temperature within the range of (± 2 ° F). Therefore, the temperature rise control of the liquid running between the mold pipes must be accurate, otherwise the mold temperature
The purpose of degree control cannot be achieved. The control method of some mold temperature controllers belongs to the on / off form, and its working principle is to compare the actual and set temperature. If the actual temperature is set
The temperature is much lower, and the electric heating is fully turned on. When the actual temperature reaches the set value, the electric heating is turned off. Due to the on / off control, a large actual positive and negative temperature deviation occurs. This temperature changes
The chemical not only directly affects the temperature of the liquid, but also indirectly brings a large excessive lifting of the mold. Needless to say, it must be reflected in the quality of the final product. So we should use PID (proportion
, Integral, differential) heating control system, which can ensure that the temperature control of the mold is maintained within the range of ± 1 ° C (± 2 ° F).
The difficulty of this chapter is mainly to learn some related calculation methods of the mold temperature machine, so it also uses a large space to elaborate! The purchase of a mold temperature machine is the same as the purchase of a chiller, which is the best fit, so you must master the necessary calculation formulas.
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