1.Determine the Cooling Requirements of the Injection Molding Machine

• Calculate the Heat Load:

During the operation of an injection molding machine, a large amount of heat is released when the plastic changes from a molten state to a cooled and solidified state. The formula for calculating the heat load (kW) is usually: , where is the mass of the plastic injected each time (kg), is the specific heat capacity of the plastic (kJ/(kg·°C)), and is the temperature difference between the melting temperature and the demolding temperature of the plastic (°C). For example, for common polypropylene (PP) plastic, the specific heat capacity is approximately . If 1 kg of PP plastic is injected each time, with a melting temperature of 200 °C and a demolding temperature of 40 °C, then the heat load . Since 1 kW = 1 kJ/s, assuming the cooling time is 10 s, the required cooling capacity is approximately.

• Consider the Size and Complexity of the Mold:

Larger molds or those with complex internal structures require more cooling medium to ensure uniform cooling. Generally speaking, the larger the mold, the greater the cooling capacity required. For example, a small injection molding mold (with dimensions smaller than 300 mm×300 mm×300 mm) may require a cooling capacity of 3 – 5 kW, while a large injection molding mold for automotive parts (with dimensions larger than 1000 mm×1000 mm×1000 mm) may require a cooling capacity of 30 – 50 kW.

2.Pay Attention to the Specification Parameters of the Injection Molding Machine

• Clamping Force:

The clamping force is a key parameter of the injection molding machine, which is related to the size of the injection molding machine and the size of the products it can produce. Usually, the larger the clamping force, the larger the specification of the injection molding machine, and the greater the cooling capacity required for the chiller. For example, an injection molding machine with a clamping force between 100 and 300 tons may be paired with a chiller with a cooling capacity of 8 – 15 kW; while a large injection molding machine with a clamping force exceeding 1000 tons may require a cooling capacity of 30 – 50 kW.

• Injection Volume:

The injection volume reflects the amount of plastic injected by the injection molding machine each time. The larger the injection volume, the higher the energy required for cooling. Generally, it can be estimated according to the amount of cooling capacity required for each kilogram of plastic. For example, approximately 10 – 15 kW of cooling capacity is needed to cool each kilogram of plastic (this is only a rough estimate, and it will actually vary depending on factors such as the type of plastic).

3.Consider Production Efficiency and Cycle Time

• Production Speed:

If the injection molding machine has a high production speed and a short cycle time, then the number of cooling requirements per unit time will be high, and the requirements for the cooling capacity and response speed of the chiller will be high. For example, a high-speed injection molding machine that can complete 3 – 5 injection cycles per minute requires the chiller to be able to quickly remove heat to ensure the cooling effect of each cycle.

• Proportion of Cooling Time in the Cycle:

It is important to understand the proportion of cooling time in the entire cycle during the injection molding process. If the cooling time accounts for a large proportion, a more powerful cooling capacity is needed to shorten the cooling time and improve production efficiency. For example, when the cooling time accounts for more than 50% of the cycle, it is necessary to ensure that the cooling capacity of the chiller can fully meet the need for rapid cooling during this period.

4.Requirements for Temperature Control Precision

• Product Quality Requirements:

For some injection molded products with high requirements for dimensional accuracy and appearance quality, such as the casings of electronic products and precision optical parts, precise mold temperature control is required. In this case, a chiller with high temperature control precision should be selected, and generally, the temperature should be controlled within ±1 – ±2 °C. For some products with relatively low requirements for dimensional and appearance accuracy, such as ordinary plastic toys, a temperature control precision within ±3 – ±5 °C may be sufficient.