As we all know, chiller is widely used, of which one is the application of plastic mold cooling, basically most of the plastic mold factory are essential chiller this device, so here to you in detail in the production of the mold How to choose the right chiller.In addition because the injection molding machine is often used together with the chiller, so inevitably introduced here.
One. How to match the chiller
In fact, a mold is a heat exchanger, the heat from the molten plastic into the mold, and then from the mold into the circulating cooling medium - ice water, only a small part of the air and injection molding machine into the template. As we all know, plastic molding cycle, a considerable part of the cooling, and sometimes can account for more than 80% of the plastic molding cycle, so the cooling time to a minimum is absolutely necessary.
For example, a mold forming cycle is generally 20 seconds, such as the original cooling tower water to chilled water machine with chiller cooling, it can be shortened to 16 seconds.Although the initial choice of chiller with higher cost, but it Can increase the output by 20%, in long-term production, can make great gains.
So, how to choose the energy of ice water? From the above we can see that it with the specific heat capacity of the molding material, melt the temperature, weight, and product release temperature.
General injection molding mold cooling, ice water pressure to choose 0.1--0.2Mpa, to meet the requirements, and microcomputer full-function chiller to meet this requirement, when the pressure requirement is higher than 0.2Mpa, need to be planned separately to facilitate the use of the corresponding pressure The water pump to meet the needs of the system water.
Flow and diameter of the relationship between the table:
The ice water energy required by a mold is calculated as: q = w × c × t × s
formula:
q is the required ice water energy kcal / h;
w plastic raw material weight kg / h;
c is the specific heat of plastic raw material kcal / kg ℃;
t is the temperature difference between the melt temperature and the mold release;
s for the safety factor (generally take 1.35 - 2.0), when a single matching, the general choice of small, and when a chiller and more molds to take large value, such as the choice of air-cooled chiller, s Should be appropriately selected a large point.
For example: a mold production of pp products, the production capacity of about 50kg per hour, asked how much cooling requirements? Should be matched with the number of chillers for the appropriate q = 50 × 0.48 × 200 × 1.35 = 6480 (kcal / h); Hours need 6480kcal / h cooling capacity, optional ls203s chiller can be.
In the actual selection of chiller, it is difficult to obtain a more complete data.According to experience, t = 200 ℃, it is many commonly used products after years of statistics after an average.
If the mold with hot glue, hot glue should also be added to the calculation of cold energy, the general hot glue is kw unit, the unit should be calculated into kcal / h, 1kw = 860kcal / h.
It is generally not practical to supply chillers with sufficient quantities of water, lower temperatures and lower costs, at this time, unless the plant can be located at a relatively large lake with low water temperature and the other is to utilize Urban deep well water supply to meet the needs of temperature and flow, but often costly.This method can be used for the experimental device, but for the factory, this is impractical.
Second, the temperature difference between ice and water
Plastic mold cooling fluid (ice water) temperature generally subject to processing materials and product shape and the larger changes, such as polystyrene thin-walled beaker, the mold requires ice water temperature below 0 ℃; while the other most cases, The temperature of ice water required by the mold is above 5 ℃. The microcomputer full-function chiller can provide ice water above 5 ℃. The low-temperature intelligent temperature chiller can meet the requirements below 5 ℃ and below 0 ℃.
Plastic mold import and export of ice water temperature is often based on product requirements to set, in many cases, the temperature is 3-5 ℃ is the best, but sometimes also need temperature difference in 1-2 ℃. The smaller the temperature difference , Means that the same heat to take out, the greater the required flow of ice water, on the contrary, the required flow is small.For example: the temperature difference is 5 ℃, the flow needs 60l, and the temperature difference is 2 ℃, the flow will need 150l .
Third, ice water flow
A plastic mold required ice water flow directly with the mold to take away the heat and ice water temperature into the mold on the difference.For example: To 6480kcal / h heat away from the mold, if the temperature difference is 3 ℃, then at least What is the required flow? Ice water flow q = 6480 ÷ 3 ÷ 60 = 36 (l / min).
Fourth, the theory of ice water quality
Water softening, in the process of using a chiller, is also a problem that can not be ignored, the pH of the water also need to constantly observe the best pH value should be equal to 7, greater than 7 ph value will have terrible corrosion, If no measures will be in the evaporator, mold dirt, will play a role in insulation, serious, so that the energy conversion effect of reducing 30%. Obviously this requires the consideration of the softening of hard water.
The most effective way to configure an electronic hard water softener system in the system is based on the exchange principle design and production.According to different flow can be configured with different specifications softener directly connected to the circulating water pipeline , The general configuration of the water treatment softener costs will not be too high, but also regular cycle system to add a certain percentage of descaling agent.
V. Ice machine flow, pressure
General injection molding mold cooling, ice water pressure of 0.1-0.2mpa, to meet the requirements, and microcomputer fully functional chiller to meet this requirement, when the pressure requirement is higher than 0.2mpa, need to be planned separately, to facilitate the use of the corresponding pressure From the pump to meet the needs of the system water supply.
VI hydraulic oil and cartridge feeding section cooling
Usually the hydraulic oil and the cylinder feed section are cooled by the water of the cooling tower, as this is not only the best method, but also economical with the cost of production, unless it has specific requirements for its temperature, Cool.
Seven. Ice water pipe insulation
Ice water pipes must be insulated because the insulation of the pipes not only prevents the serious loss of cooling capacity but also prevents the dew condensation water formed on the outer wall of the pipe.For example, ice water temperature is 10 ℃, ambient temperature is 30 ℃, Radiant heat of metal pipes 25 meters long and 25 meters in surface area can reach 750 kcal / h, which is about 10% of the capacity of a 3hp compressor and about 6% of a 5hp compressor.
Chiller and plastic mold connections, usually using enhanced hose connections, because this hose itself has the function of insulation, but the length of more than 5m, but also consider the appropriate insulation properties in the use of water chillers are Another device is closely related, that is, injection molding machine, then since the association so big, then how to match the injection molding machine, let us introduce below:
How to match the chiller and injection molding machine?
Domestic vertical, horizontal injection molding machine under normal ambient temperature conditions, water-cooled chiller cooling water condensation temperature below 35 degrees, (air-cooled chiller condensation temperature below 43 degrees) match.
A. The first way:
1hp water-cooled chiller can be equipped with 80 tons clamping force injection molding machine temperature control at 5-10 degrees;
1hp water-cooled chiller can be equipped with 100 tons clamping force injection molding machine temperature control at 10-15 degrees;
1hp water-cooled chiller can be equipped with 120 tons clamping force injection molding machine temperature control at 15-20 degrees;
(With air-cooled chiller 0.8 times the water-cooled chiller, 1HP air-cooled chiller can be equipped with 64 tons clamping force of the injection molding machine temperature control 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 volume 1QZ = 28.5g
The above formula is the result of the study concluded that in addition to using the above formula, the clerk should filter the actual situation, choose the right chiller.
C. chiller and cooling tower matching:
According to experience, 1HP chiller needs a cooling tower of 1.2 tons of cold water to take away the heat generated by the chiller.