How to Select Water Chiller Tank Capacity: Fit Injection Molding Machine Cooling Demand

water chiller

2025/11/26 By le zhan

The cooling system in injection molding is a crucial element for stable performance. The water tank capacity of the water chiller is more than just a number; it determines the balance between heat dissipation and machine requirements. Insufficient capacity leads to warping and slow production cycles; excessive capacity results in wasted energy and upfront costs. In injection molding, 41% of cooling-related production problems stem from mismatched chiller tank capacity. If you’re unsure how to choose the right water chiller tank capacity to meet the cooling needs of your injection molding machine, this guide will provide the answers.

The Importance of Water Chiller Tank Capacity

Why is tank capacity the most critical factor for a water chiller—even more important than power, pump speed, or temperature range? Injection molding generates heat primarily through two methods: the molten plastic transferring energy to the mold, and the hydraulic system and motor consuming electricity.

The water chiller’s tank acts as a “thermal buffer.” It stores cooling water, ensuring a stable, constant coolant temperature for the mold and machine components. If the tank capacity is too small, the cooler cannot handle temperature peaks—the water temperature rises, the mold cannot cool the plastic quickly enough, and ultimately the parts warp or cycle times are extended. If the tank capacity is too large, the cooler needs to operate beyond its capacity to cool more water than actually required, resulting in additional energy waste each month.

4 Core Factors for Meeting Injection Molding Machine Needs

Choosing the water tank capacity for a water cooler is not simply a matter of picking a number from the catalog; it must be matched to the injection molding machine’s unique heat load. 90% of capacity-related problems can be eliminated by considering the following four factors:

Injection Molding Machine Tonnage

The tonnage of an injection molding machine is directly related to heat output. A 100-ton injection molding machine has a smaller motor, hydraulic system, and mold cavity than a 500-ton machine, and therefore requires less cooling capacity. Based on the following:

50–150 tons: 300–500 liter water-cooled chilled water tank
150–300 tons: 500–800 liter water-cooled chilled water tank
300–500 tons: 800–1200 liter water-cooled chilled water tank
Over 500 tons: 1200–2000 liter water-cooled chilled water tank (or multiple chillers in parallel)

Plastic Material

Different plastics have different insulation properties, which affect the cooling capacity required by the water chiller. Thermoplastics, such as ABS and PC, have higher insulation properties. Compared to low-heat materials such as PP or PE, they require 20-30% larger tank capacity.

For example, a 300-ton injection molding machine used to produce PC car bodies requires a 1,000-liter water-cooled tank. Why? PC has a melting point of 500°F and a slow heat dissipation rate—smaller tanks cannot buffer this continuous energy transfer.

Part Thickness and Number of Cavities

Thick-walled parts have greater plastic mass, which results in more heat being released into the mold. A four-cavity mold (producing four parts at a time) generates twice the heat of a two-cavity mold. For every 5 mm increase in part thickness or doubling of the number of cavities, the tank capacity needs to be increased by 10% to 15%.

Ambient Temperature

In hot, humid workshop environments, water chillers experience higher workloads. If your workshop ambient temperature exceeds 85°F, you need to increase the tank capacity by 15% to 20%. Why? High temperatures reduce the cooling efficiency of water chillers—a larger tank can maintain a lower water temperature between cycles.

Water Chiller Tank Capacity: Step-by-Step Calculation

You don’t need complicated calculations to determine the capacity of your water chiller tank—you can get an accurate value using the following simplified formula:
Recommended Tank Capacity (L) = Baseline Capacity (calculated based on tonnage) × Material Factor × Thickness/Cavity Factor × Environmental Factor

Let’s understand this through a practical example: a 300-ton injection molding machine in a factory, using a 4-cavity mold to produce 10mm thick PC parts:

Step 1: Obtain the Baseline Capacity

300-ton machine = Baseline capacity 800–1,200 liters. We will use 1,000 liters (an intermediate value suitable for 24/7 operation).

Step 2: Apply the Material Factor

PC material = High insulation → Factor = 1.3 (30% increase). 1,000 liters × 1.3 = 1,300 liters.

Step 3: Apply Thickness/Cavity Factor

10mm thickness + 4-cavity mold → Factor = 1.2 (plus 20%). 1,300 liters × 1.2 = 1,560 liters.

Step 4: Apply Environmental Factor

90°F (32°C) workshop → Factor = 1.2 (plus 20%). 1,560 liters × 1.2 = 1,872 liters.

Final Recommendation: 1,900-liter water-cooled chiller tank.

Avoid 5 Costly Capacity Mistakes

Even with the calculation formula, small mistakes can lead to huge losses. Here are a few common pitfalls.

The Bigger the Better

A manufacturer, to be on the safe side, bought a 2,000-liter water-cooled chiller for a 200-ton injection molding machine. The result? Energy bills increased by 18% (due to the chiller unnecessarily cooling excess water), resulting in thousands of dollars of upfront waste. Overcapacity adds 10-20% to energy costs annually.

Neglecting Mold Cooling Circuit Design

Narrow cooling channels and inefficient molds restrict water flow, increasing the chiller’s operating load even with the correct tank capacity. If your molds are not cooling effectively, increase the tank capacity by 10% or upgrade the mold’s cooling circuit.

Selecting Tank Capacity Based on a Single Injection Molding Machine, Not the Entire Production Line

If a chiller cools multiple injection molding machines, the tank capacity should be determined by the total heat load, not the capacity of the largest machine. A production line containing 150-ton and 250-ton machines requires a 1200-liter tank (500 liters + 700 liters), not just the baseline capacity of the 250-ton machine.

Choosing the Right Chiller Tank Capacity

Choosing the right water chiller tank capacity depends on the heat load of the injection molding machine. A tank that efficiently buffers and dissipates heat should be selected. Insufficient capacity will lead to waste accumulation, extended production cycles, and operator frustration; excessive capacity will result in wasted upfront costs and energy. If you are unsure of your production capacity needs, Topstar will analyze your situation and recommend a water chiller that meets both current and future requirements.

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How to Select Water Chiller Tank Capacity: Fit Injection Molding Machine Cooling Demand

The Importance of Water Chiller Tank Capacity