Many manufacturers now use mold temperature machines. Do you know how to choose the model of the mold temperature machine? Nagin Machinery tells you how to choose and calculate correctly:
Mold temperature machine: / Deng's
When selecting a mold temperature controller, the following points are the main considerations:
1. Pump size and capacity. 2. Internal throat size. 3. Heating capacity. 4. Cooling capacity. 5. Control form.
A, the size of the pump
From the known heat dissipation per cycle, we can easily calculate the required volumetric flow rate of the coolant, and then get the correct cooling capacity required.
Most manufacturers of mold temperature control machines (mould temperature machines) provide a formula for calculating the pump flow rate of Zui. It is useful when selecting a pump, it is accurately listed.
The heat dissipation capability of different plastics.
Here are the rules of thumb for determining the pump's low flow rate:
If the temperature difference across the surface of the cavity is 5 ° C, the temperature difference of 0.75 gal / min / kW @ 5 ° C or 3.4151 / min / kW @ 5 ° C temperature difference
If the temperature difference across the surface of the cavity is 1 ° C, then the required low flow rate of Zui needs to be multiplied by five times, which is 3.75 gal / min / kW or
17.031/min/kW. In order to obtain the stability of product quality, many injection molding companies should control the temperature difference of the cavity surface to 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 range of temperature difference is 5-8 ° C.
To calculate the volumetric flow rate required for the coolant, the following procedure should be used:
1. First calculate the heat to be removed from the city where a plastic/mold combination is used: If the PC cup mold is taken as an example, the actual heat that needs to be dissipated is:
A module gross weight (g) / cooling time (s) = 208 / 12 = 17.33g / s
The heat dissipation rate of PC is =368J/g or 368kJ/kg.
Therefore, the heat that needs to be dissipated per cycle = 368 × 17.33 / 1,000 = 6.377 kW
2. Recalculate the volumetric flow rate required for cooling:
According to the above rule of thumb, if the temperature difference of the cavity surface is 5 ° C, the flow rate = 6.377 × 0.75 = 4.78 gal / min or = 6.377 ×
3.41=21.751/min If the temperature difference of the cavity is 1 °C, the flow rate = 4.78 × 5 = 23.9 gal / min or = 21.75 × 5 = 108.731 / min
3. Pump flow rate regulations:
In order to get a good heat dissipation effect, the flow rate capability of the pump should be 10% less than the calculated result, so use 27gal/min or 120/min.
Pump.
4. Pump pressure regulations:
The general mold temperature control machine (mould temperature machine) operates at 2-5 bar (29-72.5 psi), which affects the coolant due to insufficient pressure.
Volume flow rate (flow resistance creates pressure loss), so the higher the pump pressure, the more stable the flow rate.
For molds with very small cooling pipes (for example, pipe diameters of 6mm/0.236in), the pump pressure needs 10bar (145psi) to provide enough
Enough heat dissipation speed (ie, coolant speed).
In general, the higher the liquid volume requirement of the coolant, the smaller the diameter of the pipe, the greater the pump output pressure required.
The temperature of the warmer (mould temperature machine) should exceed 3bar (43.5psi).
B, heating capacity
The heating calculation table provided by Nagin Machinery provides the amount of heating required for the weight of the mold. For heating calculations:
1. The vertical axis represents the weight of the mold.
2. The horizontal axis represents the heat of the mold to the required temperature, in kW/hr.
3.37 °C-121 °C temperature ramp provides the relationship between the mold weight and the heating capacity of the mold temperature control machine (mold temperature machine) at the corresponding temperature.
For example, we can find out from the map:
1. The heating capacity required to raise the weight of the 500kg mold to 50 °C is 3.3kW / hr.
2. The heat capacity required to raise the temperature of the 700kg mold to 65 °C is 6.5kW / hr.
In general, the stronger the heating capacity, the lower the heating time required (the heating capacity is doubled and the heating time is reduced).
The tool provides a useful information for the injection molding manufacturer, and can immediately find out the heating requirements of any mold, so as to obtain the correct mold temperature control machine (mode
The heating capacity of the warming machine is often because the ability of the mold temperature control machine (mould temperature machine) is too low, causing the mold to fail to reach the good temperature state of the zui.
To know the actual performance of the mold temperature control machine (mould temperature machine), we can compare its actual and calculated mold heating time.
C, freezing capacity
The design of the freezing circuit of the mold temperature control machine (mold temperature machine) and the precise control of the component parts on the mold temperature are important. When the temperature of the mold or heating liquid
When the temperature rises to the set value, the mold temperature controller (mould temperature machine) must be able to quickly and effectively avoid the temperature from rising, by introducing another lower
The temperature of the liquid, the control of its introduction is the responsibility of the solenoid valve. Therefore the elimination and stability of the temperature override depends on the size of the solenoid valve.
The aperture of the cooling solenoid valve can be calculated using the following formula:
Freezing capacity (gal/min) = kW × 3.16 / Δt
Here Δt=the difference between the production temperature and the chilled water temperature set by the mold temperature controller:
kW = the heat that the mold needs to remove
The following table lists the volumetric flow rates available for different solenoid valve bore sizes:
Solenoid valve aperture volume flow rate
In mm gal/min 1/min
0.250 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 freezing capacity, you can find the corresponding solenoid valve from the above table, as shown in the following example:
The heat that the PC cup mold needs to drain is 6.377 kW.
The set temperature of production is 90 ° C
The temperature of chilled water is 18 ° C
△T=90-18=72°C
Therefore, the freezing capacity = 6.377 × 316 / 72 = 0.28 gal / min or 1.271 / min
From the above table, it can be known that the solenoid valve with a hole diameter of 6.35mm/0.250in can provide sufficient volume flow rate, and is suitable for the mold temperature control range of ±1 °C.
Accurate requirements. The pressure drop of the solenoid valve affects the flow rate. The flow rate values ​​in the above table are based on a pressure drop of 1 bar (14.5 psi). So the pressure drop
The higher the chilled water, the faster the flow rate. The typical pressure drop of a solenoid valve is 2 bar (29 psi).
D, liquid mold temperature heating control system
The main purpose of any mold temperature control machine (mould temperature machine) is to control the mold temperature within the range of (±2 °F). So for running on the mold
The temperature rise control of the liquid between the pipes must be precise, otherwise the purpose of mold temperature control can not be achieved.
The control method of some mold temperature control machine (mold temperature machine) is in the on/off form, and its working principle is to compare the actual and set temperature.
The temperature is much lower than the set temperature, and the electric heat is fully opened. When the actual temperature reaches the set value, the electric heat is turned off due to the on/off form.
The control produces a large actual positive and negative temperature deviation. This temperature change does not directly affect the temperature of the liquid, but also indirectly gives the mold
With a lot of excessive lifting, it is not necessary to say that after the Zui will be reflected in the quality of the finished product.
Therefore, we should use a heating control system in the form of PID (proportional, integral, differential), which can ensure that the temperature control of the mold is maintained at ±1 °C.
Within the range of (±2°F).
Choose the appropriate mold temperature control machine (mold temperature machine)
Indiscriminate purchase of mold temperature control machine (mould temperature machine) can bring 20% ​​profit loss at any time, so Najin Machinery must consider production in detail when purchasing
The need to strictly examine the ability of the mold temperature control machine (mould temperature machine), we have to make a decision. Unfortunately, people often overlook this injection molding technology
Its important links are often awakened when there is a problem with productivity and quality.
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