Plastic mold with water chiller(1)

Plastic mold with water chiller(1)

1. How to choose a chiller

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In fact, a mold is a heat exchanger. The heat is transferred from the melted plastic to the mold, and from the mold to the circulating cooling medium -- ice water. As we all know, the plastic forming cycle, some are quite large for cooling, sometimes accounting for more than 80% of the plastic forming cycle, so it is absolutely necessary to control the cooling time to the minimum. For example, the molding cycle of a mold is usually 20 seconds. If the water from the cooling tower is changed to the cold water from the chiller, it can be shortened to 16 seconds. Although it is more expensive to start selecting a chiller, it can increase the output value by 20%, which can bring great benefits over a long period of time. So how do you pick ice water energy? From above we can know that it is related to the specific heat capacity of the forming data, the temperature of melting glue, the component and the temperature of the finished product when it comes out of the mold. General injection mold cooling, ice water pressure select 0.1 -- 0.2Mpa, can be satisfied with the request, and microcomputer full function cold water function satisfied with this request, when the pressure request is higher than 0.2Mpa, need to plan separately, in order to select the corresponding pressure of the pump to meet the needs of the system water supply. plastic mold

Connection table between flow rate and pipe diameter:

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Q =w×c×t×s is used to calculate the ice water energy required for a moldIn the formula:

Q is kcal/h of required ice water energy;

W is the weight of plastic raw materials kg/h;

C is kcal/kg℃ for specific heat of plastic raw materials;

T is the temperature difference ℃ between the melting glue temperature and the mold release of the finished product;S is the safety factor (generally 1.35 -- 2.0). When a single machine is matched, a small value is generally selected, while when a chiller is matched with multiple molds, a large value is selected. For example, when selecting an air-cooled chiller, s should also be appropriately selected as a large value. For example, a pair of molds produces pp products, with an output value of about 50kg per hour. What is the cooling requirement? What size chiller should be fitted?Q =50×0.48×200×1.35 = 6480 (kcal/h);6480kcal/h cooling capacity per hour, ls203s chiller can be used.

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In the process of selecting chiller in practice, it is difficult to get good data. According to our previous plans and sales experience, t = 200℃, which is an average value of many common finished products after years of calculation. If there is hot glue track on the mold, the energy of hot glue track should also participate in the calculation of cold quantity, the general hot glue track is a unit of kw, 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, it is not necessary to use the chiller at the moment. The other is to use urban deep well water supply to meet the needs of temperature and flow, but often the cost is too high. This approach can be applied to test equipment, but in the case of factories, it is not practical to do so. plastic mold

 

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