How to match the chiller with plastic molds and injection molding machines
As we all know, chillers are widely used, and one of them is the cooling of plastic molds. Basically, most plastic mold production plants are indispensable to the chiller, so today I will specifically introduce you here. How to choose a suitable chiller in the production of molds. In addition, since injection molding machines are often used together with chillers, it is inevitable to introduce them here.
1. How to choose a chiller
In fact, a mold is a heat exchanger. The heat is transferred from the molten plastic to the mold, and then from the mold to the circulating cooling medium-ice water. Only a small amount enters the air and the pressure of the injection molding machine. template. As everyone knows, some of the plastic molding cycle is quite large for cooling, and sometimes it can account for more than 80% of the plastic molding cycle. Therefore, it is absolutely necessary to control the cooling time to a small z*. For example, the molding cycle of a mold is generally 20 seconds. If the water in the cooling tower is changed to ice water generated by a chiller, it can be shortened to 16 seconds. Although it is more expensive to select and equip the chiller at the beginning, it can increase the output value by 20%, and can obtain great benefits in the long-term production.
So, how to choose ice water energy? From the above, we can know that it is related to the specific heat capacity of the molding material, the temperature and weight of the melt when the glue is melted, and the temperature when the finished product is demolded.
Generally, the injection molding mold is cooled, and the ice water pressure can be selected from 0.1 to 0.2Mpa to satisfy the request, and the microcomputer full-function chiller can satisfy this request. When the pressure request is higher than 0.2Mpa, another plan is required to facilitate the selection of the corresponding pressure The water pump meets the needs of the system for water supply.
The connection table between flow and pipe diameter:
The formula for calculating the ice water energy required by a mold is: q=w×c×t×s
In the formula: q is the required ice water energy kcal/h;
W is the weight of plastic raw material kg/h;
C is the specific heat of plastic raw material kcal/kg℃;
T is the temperature difference ℃ between the melt temperature and the finished product demoulding;
s is the safety factor (usually 1.35—2.0). When a single machine is matched, a small value is generally selected, and a large value is used when a chiller is matched with multiple molds. For example, when an air-cooled chiller is selected, s is also It should be selected appropriately.
For example: a mold produces pp finished products, and the output value per hour is about 50kg. What is the cooling requirement? What size water chiller should be equipped with? q=50×0.48×200×1.35=6480 (kcal/h); cooling capacity of 6480kcal/h per hour is required, and ls203s chiller can be used.
In the process of selecting the chiller in practice, it is difficult to obtain comparatively good data. According to our previous years of planning and supporting sales experience, t=200℃, which is an average value of many commonly used products after years of calculation.
If there is a hot glue path attached to the mold, the energy of the hot glue path should also be included in the calculation of the cooling capacity. Generally, the hot glue path is in kw, and the unit should be converted to kcal/h when calculating, 1kw=860kcal/h. If the water supply to the factory is sufficient, the temperature is low, and the cost is low, there is no need to use a water chiller at this moment. This is generally not practical unless the factory can be located near a large lake with a low water temperature; the other is to use a city Deep well water supply meets the needs of temperature and flow, but the cost is often too high. This method can be used for test equipment, but it is impractical for factories to do so.
2. Ice water temperature difference
The temperature of the plastic mold cooling fluid (ice water) is generally affected by the processing materials and the shape of the finished product. For example, a polystyrene thin-walled beaker, the mold requires the ice water temperature to be below 0°C; in most other cases, The temperature of the ice water requested by the mold is above 5℃, the microcomputer full-function chiller can provide ice water above 5℃, and the low-temperature intelligent temperature control chiller can satisfy the request below 5℃ and below 0℃.
The temperature difference of the ice water at the entrance and exit of the plastic mold is often set according to the requirements of the finished product. In many cases, the temperature difference is 3-5℃ is ideal, but sometimes the temperature difference is 1-2℃. The smaller the temperature difference, it means that the same amount of heat is taken out, the larger the flow of ice water is required, and vice versa. 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.
Three, ice water flow
The flow of ice water required for a plastic mold is directly related to the heat that the mold takes away and the temperature difference between the ice water in and out of the mold. For example: To take away the heat of 6480kcal/h from the mold, if the temperature difference is 3℃, what is the flow rate required for ? The ice water flow q=6480÷3÷60=36 (l/min).
Fourth, the theory of ice water quality
The softening of water is also a question that cannot be ignored in the process of using the chiller. The ph value of water also needs to be constantly observed. The z*good ph value should be equal to 7, and the ph value greater than 7 will cause terrible corrosion. If the method is not adopted, scale will form in the evaporator and mold, which will play a role of heat insulation. When severe, its energy conversion effect will be reduced by 30%. Obviously, this requires thinking about the softening of hard water. z*An effective way is to equip an electronic hard water softener in the system. Such a softener is manufactured based on the principle of communication. Depending on the flow rate, different standard softeners can be equipped, and they can be directly connected to the circulating water pipeline. Generally, the cost of installing a water treatment softener is not too high. It can also participate in a certain amount of deduction in the circulation system at a certain period of time. Scale agent.
5. Ice water machine flow and pressure
Generally, the injection molding mold is cooled, and the ice water pressure is selected from 0.1 to 0.2mpa to satisfy the request. The microcomputer full-function chiller can satisfy this request. When the pressure request is higher than 0.2mpa, another plan is required to facilitate the selection of the corresponding pressure From the water pump to meet the needs of the system water supply.
6. Cooling of hydraulic oil and barrel feeding section
Generally, the hydraulic oil and barrel feeding section are cooled by cooling water tower water. Because this is not only the best way, it is only cost-effective, but also extremely economical. Unless there are specific requirements for its temperature, ice water can be used for cooling. It is cooled.
Seven, ice water pipe insulation
Ice water pipes must be thermally insulated, because pipe insulation can not only prevent severe loss of cold capacity, but also prevent condensation formed on the outer wall of the pipe. For example: the temperature of ice water is 10℃, the ambient temperature is 30℃, the heat radiation of a 25-meter-long metal pipe with a surface area of 25m2 can reach 750kcal/h, which is almost 10% of the cooling capacity of a 3hp compressor, 5hp The compressor produces 6% of the cooling capacity.
The connection between the water chiller and the plastic mold is generally used to connect with a reinforced hose. Since such a hose has the function of heat insulation, but the length exceeds 5m, it is necessary to consider moderate heat insulation. In the application of the chiller, it is closely related to another equipment, that is, the injection molding machine. Since the correlation is so large, how to choose an injection molding machine, let us introduce you:
How to choose a chiller and injection molding machine?
The domestic vertical and horizontal injection molding machines are matched when the cooling water condensation temperature of the water-cooled chiller is below 35 degrees (the condensation temperature of the air-cooled chiller is below 43 degrees) under the normal ambient temperature operation.
A. The first method:
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 1HP air-cooled chiller can be equipped with a 64-ton injection molding machine with a clamping force. The temperature is controlled at 5-10 degrees.)
B. The second method:
1HP water-cooled chiller can be equipped with a single injection molding volume of 10 QZ injection molding machine temperature control at 5-10 degrees.
Injection amount 1QZ=28.5g
The above formula is the result summarized by the thoughts. In addition to using the above formula, the salesperson should consider the filtering practice and select the appropriate chiller.
C. The matching of chiller and cooling tower:
According to previous practice, a 1HP chiller needs a 1.2-ton cooling water tower to take away the heat generated by the chiller
