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Torsten’s Training Tip: Parallel and Serial Coolant Circuits

by Torsten Kruse

An injection mold is effectively a heat exchanger. Molten polymer material that is injected must be cooled by the mold cooling system. As part designs become more complex, cavitation requirements increase, and larger overall mold bases are needed. Mold designers have several options when designing effective heat removal systems.

Coolant circuits can be parallel or connected as a series. In serial circuits, individual channels are connected inside the mold or by hoses to loop circuits outside the mold. In this case the overall flow length may lead to higher flow resistance and higher coolant pressure requirements. Longer circuits can present a few potential problems such as significant inlet-to-outlet coolant temperature differences which could create mold temperature distribution inconsistences. Long circuits may have more scale build-up and are also harder to clean.

An important aspect of coolant line layout design is evaluating a plant’s water supply or a machine-side chiller and temperature control unit to assess whether they can deliver appropriate water flow for a tool.

Designing effective mold cooling circuits depends on mold cavitation, coolant circuit sizes, layout and flow length, circuits looping, distribution manifold design and size, and the available flow rate and coolant pressure.  Complex and long coolant channel flow lengths and sizes require higher pressures and can possibly lead to increased coolant temperatures.

Mold designers should incorporate coolant CFD simulations for complex mold designs to ensure adequate coolant flow behaviors to effectively cool molds and ensure the highest part quality in the shortest possible cycle time.

Kruse Training offers a full section of Cooling lessons. You can purchase individual lessons or the full set.

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