As we all know, industrial chillers are widely used, an […]
As we all know, industrial chillers are widely used, and one of them is the cooling of plastic molds. Basically, most plastic mold production plants are indispensable for the chiller. Today, the editor will specifically introduce you to the mold. How to choose a suitable chiller in production.
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 part of it enters the air and the die plate of the injection molding machine. . As we all know, a considerable part of the plastic molding cycle is used for cooling, sometimes accounting for more than 80% of the plastic molding cycle. Therefore, it is necessary to control the cooling time to the minimum. For example, the molding cycle of a mold is generally 20 seconds. If the water in the original cooling tower is replaced with ice water generated by a chiller, it can be shortened to 16 seconds. Although the cost of the initial selection of the equipment chiller is higher, 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, and the temperature when the product is demolded.
Generally, the injection molding mold is cooled, and the ice water pressure is 0.1-0.2Mpa, which can meet the requirements, and the microcomputer full-function chiller can meet this requirement. When the pressure requirement is higher than 0.2Mpa, separate planning is required to facilitate the selection of the corresponding pressure The pumps meet the needs of the system's water supply.
The formula for calculating the ice water energy required for a mold is: q=w×c×t×s.
In the formula: q is the required ice water energy kcal/h.
W is the plastic raw material weight kg/h.
C is the specific heat of plastic raw material kcal/kg°C.
T is the difference °C between the melt temperature and the temperature when the product is demolded.
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 products, and the production value per hour is about 50kg. What is the cooling demand? What size chiller should be suitable? q=50×0.48×200×1.35=6480 (kcal/h). 6480kcal/h cooling capacity is required per hour, and ZYW-02 chiller can be used.
In the process of selecting chillers in practice, it is difficult to obtain relatively complete 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 lane attached to the mold, the energy of the hot glue lane should also be added to the calculation of the cooling capacity. Generally, the hot glue lane is in kw, and the unit should be converted into kcal/h, 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 chiller at this time. This is generally not realistic unless the factory can be located by a large lake with a relatively low water temperature. The other is to use urban deep well water supply to meet the temperature and flow demand, but the cost is often too high. This method can be used for experimental equipment, but it is impractical for factories to do so.
2. the ice water temperature difference.
The temperature of the plastic mold cooling fluid (ice water) generally changes greatly due to the processing material and product shape, such as polystyrene thin-walled beakers, the mold requires the ice water temperature to be below 0°C. In most other cases, 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, and the low-temperature intelligent temperature control chiller can satisfy the requirements below 5°C and below 0°C. Requirements.
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 product. In many cases, the temperature difference of 3-5℃ is the best 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, and the required flow of ice water is greater, and vice versa. For example: when the temperature difference is 5℃, the flow demand is 60l, and when the temperature difference is 2℃, the flow demand is 150l.
3. 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 the heat of 6480kcal/h away from the mold, if the temperature difference is 3℃, what is the minimum required flow rate? Ice water flow q=6480÷3÷60=36 (l/min).
4, the theory of ice water quality.
The softening of water is also a problem that cannot be ignored in the process of using the chiller. The ph value of water also needs to be continuously observed. The best ph value should be equal to 7, and the ph value greater than 7 will cause terrible corrosion. If no measures are taken, fouling will form 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 the softening of hard water. *An effective method is to configure an electronic hard water softener in the system. Such a softener is planned and manufactured based on the principle of exchange. Depending on the flow rate, different specifications of softeners can be configured and directly connected to the circulating water pipeline. Generally, the cost of configuring a water treatment softener will not be too high, and a certain proportion of descaling agent can also be added to the circulating system during a fixed period .
5. The flow and pressure of the chiller.
Generally, the injection molding mold is cooled, and the ice water pressure is 0.1-0.2mpa to meet the requirements, and the microcomputer full-featured water chiller can meet this requirement. When the pressure requirement is higher than 0.2mpa, separate planning is required to facilitate the selection of the corresponding pressure from The water pump meets the demand of the system for water supply.
6. Cooling of hydraulic oil and barrel feeding section.
Generally, the hydraulic oil and barrel feeding section use cooling water tower water for cooling. Because this is not only the best method, it is cost-effective for production, but also extremely economical. Unless there are specific requirements for its temperature, ice water can be used for it Cool down.