How to choose the chiller for the injection molding machine?
Author: Beijing Hengxing and Technology Co., Ltd. Source: http: //
When the domestic vertical and horizontal injection molding machines are used under normal ambient temperature conditions, the cooling water condensation temperature of the water-cooled chiller is below 35 degrees, and the matching of the air-cooled chiller condensing temperature is below 43 degrees.
A: The first way:
1hp water-cooled chiller can be equipped with 80 tons of clamping force injection molding machine temperature control at 5-10 degrees;
1hp water-cooled chiller can be equipped with 100 tons of clamping force injection molding machine temperature control at 10-15 degrees;
1hp water-cooled chiller can be equipped with 120 tons of clamping force injection molding machine temperature control at 15-20 degrees;
(The matching of the air-cooled chiller is 0.8 times that of the water-cooled chiller, that is, the temperature of the 1HP air-cooled chiller can be matched with 64 tons of clamping force. The temperature of the injection molding machine is controlled at 5-10 degrees.)
B: The second way:
1HP water-cooled chiller can be equipped with a single injection volume of 10 QZ injection molding machine temperature control at 5-10 degrees.
Injection quantity 1QZ=28.5g
The above formula is the result of the experience summary. In addition to the above formula, the salesman should filter the actual situation and choose the appropriate chiller.
C: matching of the chiller and the cooling tower,
According to the actual experience of the 1HP chiller, a 1.2 ton cooling tower can take away the heat generated by the chiller.
One. How to fit a chiller In fact, a pair of molds is a heat exchanger, heat is transferred from the molten plastic to the mold, and then the mold is introduced into the circulating cooling medium - ice water, only a small part of which enters the air and is injection molded. Pressing template of the machine. It is well known that plastic molding cycles, a considerable portion for cooling, sometimes account for more than 80% of the plastic molding cycle, so it is absolutely necessary to control the cooling time to a minimum. For example, a mold molding cycle generally takes 20 seconds. If the water in the original cooling tower is changed to the ice water produced by the chiller, it can be shortened to 16 seconds. Although the initial choice of chiller is higher, it can increase production by 20% and achieve significant gains in long-term production. So how do you choose the energy of ice water? From the above we can know that it is related to the specific heat capacity of the molding material, the temperature at the time of melting, the weight and the temperature at which the product is demolded.
The formula for calculating the ice water energy required for a pair of molds is q=w × c × ? t × s
Where: q is the required ice water energy kcal/h;
w is the weight of the plastic raw material kg / h;
c is the specific heat of the plastic raw material kcal / kg ° C;
? t is the temperature difference between the temperature of the melt and the release of the product °C (see attached table);
s is the safety factor (generally 1.35-2.0). When the single machine is matched, the small value is generally selected. When a chiller is matched with multiple molds, the value is taken. If the air-cooled chiller is selected, s should also be Choose a larger one.
For example: a pair of molds produce pp products, the production volume is about 50kg per hour, what is the cooling requirement? What size should the chiller be suitable for?
q=50 × 0.48 × 200 ×1.35=6480(kcal/h); 6480kcal/h cooling capacity per hour, ls203s chiller can be used.
In the actual selection of chillers, it is difficult to obtain more complete data. According to our previous years of planning, supporting sales experience,? t = 200 ° C, which is an average of many common products after years of statistics.
If the hot glue path is attached to the mold, the energy of the hot glue path should be added to the calculation of the cold quantity. Generally, the hot glue path is in kw. When calculating, the unit should be converted into kcal/h, 1kw=860kcal/h. If the water supplied to the plant is sufficient, the temperature is low, and the cost is low, there is no need to use a chiller at this time, which is generally unrealistic unless the plant can be located at a lake with a relatively low water temperature; the other is Urban deep well water supplies meet the needs of temperature and flow, but often the cost is too high. This method can be used for experimental devices, but for the factory, this is impractical.
two. Ice water temperature difference mold cooling fluid (ice water) temperature is generally subject to changes in the shape of processed materials and products, such as polystyrene thin wall beakers, molds require ice water temperature below 0 ° C; and most other situations Under the mold, the temperature of the ice water required by the mold is above 5 °C. The microcomputer full-function chiller can provide ice water above 5 °C. The low temperature intelligent temperature control chiller can meet the requirements below 5 °C and below 0 °C.
The temperature difference between the ice water at the inlet and outlet of the mold is often set according to the requirements of the product. In many cases, the temperature difference is 3-5 ° C, which is ideal, but sometimes the temperature difference is 1-2 ° C. The smaller the temperature difference, the greater the flow of ice water required to bring the same amount of heat out, and the lesser flow required. For example, when the temperature difference is 5 °C, the flow rate needs 60l, and when the temperature difference is 2 °C, the flow rate needs 150l.
Third, the ice water flow The amount of ice water required for a pair of molds is directly related to the heat to be taken away by the mold and the temperature difference between the ice water entering and leaving the mold. For example: to be
The heat of 6480 kcal/h is taken away from the mold. If the temperature difference is 3 °C, what is the minimum flow required? Ice water flow q=6480 ÷3÷ 60=36(l/min).
Fourth, the softening of the water quality of ice water, in the process of using the chiller, is also a problem that can not be ignored, the ph value of the water also needs to be constantly observed, the best ph value should be equal to 7, greater than 7 ph value It will produce terrible corrosion. If no measures are taken, it will cause scale in the evaporator and mold, which will act as heat insulation. In severe cases, the energy conversion effect will be reduced by 30%. Obviously this requires consideration of softening of hard water. The most effective method is to configure an electronic hard water softener in the system. The softener is designed and manufactured according to the exchange principle. Depending on the flow rate, softeners of different specifications can be configured and directly connected to the circulating water pipeline. Generally, the cost of the water treatment softener is not too high, and a certain proportion of detergent can be added to the circulation system during the period. .
Fives. The flow rate and pressure of the ice water machine are generally cooled by the injection molding die. The pressure of the ice water is 0.1~0.2mpa, which can meet the requirements. The full-function chiller of the microcomputer can meet this requirement. When the pressure requirement is higher than 0.2mpa, it needs to be planned separately. Eli uses the corresponding pressure from the pump to meet the needs of the system water supply.
The relationship between flow and pipe diameter is shown in the table below.
six. Cooling of the hydraulic oil and barrel feed section The hydraulic oil and barrel feed sections are usually cooled by the water from the cooling tower, as this is not only the best method, but also cost-effective to produce, unless it is economical. The temperature has specific requirements and can be cooled with ice water.
Seven. Insulation of ice water pipes Ice water pipes must be insulated because the pipe insulation not only prevents the serious loss of cold, but also prevents the formation of dew condensation on the outer wall of the pipe. For example: ice water temperature 10 ° C, ambient temperature 30 ° C, a 25 m long, surface area of ​​25 m2 metal pipe heat radiation up to 750kcal / h, which is almost 10% of the 3hp compressor refrigeration capacity, 5hp compression The machine produces about 6% of the cooling capacity.
The connection between the chiller and the mold is usually connected by a reinforced hose, because such a hose itself has a heat insulating function, but the length is more than 5 m, and moderate heat insulation is also considered.
Schedule: Injection molding and mold temperature and specific heat required for different molding materials.
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