iCool® Breakthrough Design Concept: Managing Energy vs. Pumping Water at a Temperature

If you live in the injection molding world you probably are familiar with the conundrum of how to define mold temperature. Because injection molding is a cyclic continuous process, the actual molding surfaces are heating and cooling with every shot of plastic that is injected. It is a dynamic situation where the position of a sensor in the mold is only reporting that specific mold temperature for that location.

So what is the real number? Mold molding shops almost universally use the temperature setting of the TCU or its actual readout as the defacto mold temperature. The only shops not doing this are trying to implement scientific molding techniques and have designed the molds with sensors for data acquisition. Some try to take quick temperature measurements at mold opening, but as you know it’s a dynamic continuously changing temperature now that the next shot of plastic has been stopped. So, again……..what is the mold temperature? 

Energy Balance 380w

The answer is all of the measurements are real data but none of them is “the one”. Referring to the Mold Energy Process Window graphic above, while the molding machine is running an energy balance is developing with the cooling energy absorbing thermal energy from the heat energy introduced each shot from the molding machine. These energy transfers back and forth create what are called energy fluxes or flows within the mold. For example, if the cooling energy delivered each cycle varies and is trending down, then more heat will be extracted over time and all of the temperature data points we just discussed will be trending down. If you raise the plastic melt temperature five degrees, then the additional heat will cause the mold temperatures collectively to trend up.

Referring to the Mold Energy Delivery graphic below, clearly what processors want is “Stability”. When the heating energy is consistently met with a stable quantity of cooling energy, we can say the heat extraction process is stable. In Scientific molding terms, parts molded with stable cooling, repeatable melting, repeatable filling/packing parameters and consistent plastic morphology should be quite consistent.

Process Energy Delivery Flow Chart

The problem is that current technology for the most part does not control coolant flow. It only controls temperature. Since the thermal energy exchange is a product of both coolant temperature and flow, conventional TCU’s really have no definitive mold temperature control!

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