Injection machine cooling
Everyone knows that chiller is widely used. One of them is the cooling of molds. Basically, most mold production plants are indispensable with chiller. So I will introduce you to the details of How to choose a suitable chiller in production. In addition, because injection molding machines are often used with chiller, it is inevitable to introduce them here.
One. How to choose a chiller
In fact, a pair of molds is a heat exchanger. Heat is transferred from the molten plastic to the mold, and then from the mold to the continuously circulating cooling medium, ice water. Only a small part of it enters the air and the mold platen of the injection molding machine. As we all know, a considerable part of the cycle of plastic molding is used for cooling, and sometimes it can account for more than 80% of the cycle of plastic molding, so it is absolutely necessary to control the cooling time to a minimum. For example, the molding cycle of a pair of molds usually takes 20 seconds. If the water in the original cooling tower is changed to ice water generated by a chiller, it can be shortened to 16 seconds. Although the initial cost of choosing a chiller is higher, it can increase output by 20%, and it can achieve great benefits in 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 at the time of melting the glue, the weight, and the temperature at which the product is demolded.
Generally, the injection molding mold is cooled, and the pressure of ice water is selected to be 0.1 ~ 0.2Mpa, which can meet the requirements. The microcomputer full-function chiller can meet this requirement. When the pressure is higher than 0.2Mpa, it needs to be planned separately to facilitate the use of the corresponding pressure. Water pump to meet the needs of system water supply.
Relationship between flow and pipe diameter:
Pipe diameter: 3/8 ″, 1/2 ″, 3/4 ″, 1 ", 1 '/ 4 ″, 1' / 2 ″, 2 ″, 3 ″
Flow: 12, 20, 35, 60, 90, 130, 230, 560
The formula for the ice water energy required by 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 plastic raw material kg / h;
c is the specific heat of plastic raw material kcal / kg ℃;
The difference between the temperature of the melt glue and the temperature at which the product is demolded ℃;
s is the safety factor (usually 1.35-2.0). When the single machine is matched, a small value is generally selected, and when a chiller is matched with multiple molds, a large value is used. Choose a larger one appropriately.
For example: a pair of molds to produce pp products, the production capacity is about 50kg per hour, how much cooling is required? How large is the chiller? q = 50 × 0.48 × 200 × 1.35 = 6480 (kcal / h); 6480kcal / h cooling capacity is required per hour, ls203s chiller is optional.
In the actual selection of chiller, it is difficult to obtain relatively complete data. According to our past years of planning and supporting sales experience,? T = 200 ° C, which is an average value of many commonly used products after years of statistics.
If the hot glue lane is attached to the mold, the energy of the hot glue lane should also be added to the calculation of cold capacity. Generally, the hot glue lane is based on kw. When calculating, the unit should be converted into kcal / h, 1kw = 860kcal / h. If the amount of water supplied to the factory is sufficient, the temperature is low, and the cost is low, it is not necessary to use a chiller at this time, which is generally not realistic, unless the factory can be near a large lake with a relatively low water temperature; the other is to use Urban deep wells supply water to meet the needs of temperature and flow, but often the cost is too high. This method can be used for experimental installations, but it is impractical for factories.
two. Ice water temperature difference
The temperature of the mold cooling fluid (ice water) generally varies greatly due to the shape of the processing materials and products. For example, polystyrene thin-walled beakers, the mold requires ice water temperature below 0 ° C; and in most other cases, the mold The required ice water temperature 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 and water at the entrance and exit of the mold is often set according to the requirements of the product. In many cases, the temperature difference is 3-5 ° C, but it is sometimes required to be 1-2 ° C. The smaller the temperature difference means that the same amount of heat is taken out, the larger the ice water flow is required, and vice versa. For example: when the temperature difference is 5 ℃, the flow rate is 60l, and when the temperature difference is 2 ℃, the flow rate is 150l.
Three, ice water flow
The ice water flow required by 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 remove the heat of 6480kcal / h from the mold, if the temperature difference is 3 ° C, what is the minimum flow rate required? Ice water flow q = 6480 ÷ 3 ÷ 60 = 36 (l / min).
Fourth, the theory of ice water quality
The softening of water is also a problem that cannot be ignored in the process of using chillers. The pH value of water also needs to be constantly monitored. The optimal pH value should be equal to 7, and a pH value greater than 7 will cause terrible corrosion. If no measures are taken, fouling will occur in the evaporator and the mold, which will act as heat insulation. In severe cases, its 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. Such a softener is designed and manufactured based on the principle of exchange. Softeners of different specifications can be configured according to different flows, which are directly connected to the circulating water pipeline. Generally, the cost of a water treatment softener is not too high, and a certain proportion of descaling agents can be added to the circulation system in a fixed period. .
Fives. Ice water machine flow, pressure
Generally, the injection molding mold is cooled, and the pressure of ice water is selected from 0.1 to 0.2mpa, which can meet the requirements. The microcomputer full-function chiller can meet this requirement. When the pressure is higher than 0.2mpa, it needs to be planned separately to facilitate the use of the corresponding pressure. Water pump to meet the needs of system water supply.
six. Cooling of hydraulic oil and barrel feed section
Generally, the hydraulic oil and the feeding section of the barrel are cooled by the water of the cooling water tower, because this is not only the best method, wfq0803wf alone is cost-effective, and it is also extremely economical. Unless there are specific requirements for its temperature, ice water can be used. It is cooled.
Seven. Insulation of ice water pipes
Ice-water pipes must be insulated because the pipe insulation not only prevents the severe loss of cooling capacity, but also prevents the formation of dew 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 25m long metal pipe with a surface area of 25m2 can reach 750kcal / h, which is almost 10% of the cooling capacity generated by a 3hp compressor, and 5hp compression The machine produces about 6% of the cooling capacity.
The connection between the chiller and the mold is usually connected by reinforced hoses, because such hoses have the function of heat insulation, but the length is more than 5m, and moderate heat insulation must also be considered. In the use of chiller, it is closely related to another equipment, that is, the injection molding machine. Since the connection is so large, how to choose an injection molding machine, let us ask you to introduce it below.
How to choose chiller and injection machine
The domestic vertical and horizontal injection molding machines are used under normal ambient temperature conditions, and the cooling water condensing temperature of the water-cooled chiller is below 35 degrees, (the condensing temperature of the air-cooled chiller is below 43 degrees).
A: The first way: 1hp water-cooled chiller can be equipped with 80 ton clamping force injection molding machine temperature control at 5-10 degrees;
1hp water-cooled chiller can be equipped with a 100-ton clamping force injection molding machine temperature control at 10-15 degrees;
1hp water-cooled chiller can be equipped with a 120-ton clamping force. The temperature of the injection molding machine is controlled at 15-20 degrees; The temperature of the injection molding machine with tons of clamping force is controlled at 5-10 degrees.)
B: The second method: 1HP water-cooled chiller can be equipped with an injection molding machine with a single injection quantity of 10QZ to control the temperature at 5-10 degrees. The injection quantity of 1QZ = 28.5g is the result of experience. In addition to the formula, the salesman should test the actual situation and select a suitable chiller.
C: The matching of the chiller and the cooling water tower. According to the actual experience of the past, a 1HP chiller requires about 1.2 cooling tons of cooling water tower to take away the heat generated by the chiller.