The following are the main considerations;
1. Pump size and capacity.
2. The size of the internal throat.
3. heating capacity.
4. cooling capacity.
5. control form.
From the known heat dissipation required per cycle we can easily calculate the required volume flow rate of the coolant and then derive the correct cooling capacity required.
Here are some rules of thumb for determining the low flow rate the pump needs to deliver:
If the temperature difference across the cavity surface is 5°C,
0.75gal/min/kW@5℃ temperature difference or
3.4151/min/kW@5℃ temperature difference
If the temperature difference across the cavity surface is 1°C, the required low flow rate needs to be proportionally multiplied by a factor of five, 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 on the surface of the mold cavity to 1-2 °C, but in fact, many injection molding manufacturers may not know the importance of this temperature difference or think that the temperature difference is the best range. is 5-8°C.
To calculate the volume flow rate required for the coolant, the following procedure should be used:
1. First calculate the heat to be removed by planting a plastic/mold combination: if
Taking the aforementioned PC cup mold as an example, the actual heat that needs to be dissipated is:
One module gross weight (g)/cooling time (s)=208/12=17.333g/s
The heat dissipation rate of PC is = 368J/g or 368kJ/kg
So the heat to be dissipated per cycle=368×17.33/1,000=6.377kW
2. Then calculate the volumetric flow rate required for cooling:
According to the above rule of thumb, if the temperature difference between the surface of the cavity is 5°C, the flow rate=6.377×0.75=4.78gal/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=23.9gal/min or =21.75×5=108.731/min
3. Specification of pump flow rate
In order to get good heat dissipation, the flow rate capacity of the pump should be 10% less than the calculated result, so a 27gal/min or 120/min pump should be used.
4. Regulation of pump pressure;
Generally, the operating pressure of the mold temperature controller is 2-5bar (29-72.5psi). Since the volume flow rate of the coolant will be affected under the condition of insufficient pressure (the flow resistance causes pressure loss), the higher the pump pressure, the higher the flow rate. more stable.
For molds with very small cooling pipes (for example, the diameter of the pipes is 6mm/0.236in), the pressure of the pump needs to be 10bar (145psi) to provide sufficient heat dissipation speed (that is, the cooling liquid speed).
Generally speaking, the higher the volumetric liquid velocity requirement of the cooling liquid, and the smaller the diameter of the pipeline, the higher the required pump output pressure. Therefore, in general, the pressure of the mold temperature controller should exceed 3bar (43.5psi). B. The heating capacity is a typical heating calculation table, which provides the heating amount required for the weight of the mold.
In general, the stronger the heating capacity, the shorter the heating time required (double the heating capacity and less heating time). It is often because the ability of the mold temperature controller is too low that the mold cannot reach the optimal temperature state. To see how the mold temperature controller actually behaves, we can compare its actual and calculated mold warm-up time.
RICOM Refrigeration Equipment Co., Ltd. is a manufacturer specialized in industrial chiller and temperature controller technology for 20 years.
