We are going to distinguish where MoldCool’s Variotherm product fits into the scope of heating/cooling technologies that have been developed over the last few years. Recently published in the trade journal Plastics Technology, February issue there is an article announcing the new offering to the US market by Single Temperature Controls, Inc. of a new technology they call Passive Variotherm.


The article goes on to define the distinction between active and Passive Variotherm. Whereas active Variotherm is defined as “active heating and cooling from an alternating temperature-control system,” passive Variotherm is defined as simply turning the pump on and off in concert with the molding machine. The article goes on to extol all the benefits of this technique and that the well-respected Aachen University in Aachen, Germany has validated all their claims. And the fact is, their claims are true!

BoostMold Variotherm

In the February issue of Plastics Technology Magazine, Passive Variotherm is defined as:

"Passive approaches, such as Single’s EcoTemp system to be shown at NPE, interrupt water flow for mold cooling during the injection phase, so that the cavity wall heats up by conduction of thermal energy from the injected melt. This is followed by an intense cooling phase, which can use 10-20% lower water temperatures than standard constant-temperature cooling systems."

The BoostMold™ technology fits that Passive Variotherm definition.

BoostMold™ started out in the iCool®’s development as a TCU based alternative to valve controlled pulsed cooling systems which have been available in the US and Europe for more than 30 years. In a way, pulsed cooling control systems are a precursor to passive Variotherm. This is accomplished by placing a sensor in the mold cavity close to the point of gate fill so the PLC could start the cooling flow when it sensed the heat rise of the incoming melt front. The duration of the on time of the valves is determined by their proprietary software so that the mold temperature is said to be maintained. These valve control systems typically use direct chilled water and so are limited to this. Also they require a sensor located in the mold in order to operate while the iCool® does not.

The iCool® brings the sophistication of a computer driven positive displacement pump to precisely control a timed burst of cooling to the mold. It does not require the fitment of a sensor or sensors in the mold. This timed cooling burst is exactly positioned on the graphical user interface to coincide accurately with the injection start that begins after the clamp closes each cycle of the machine. The positioning of the delivery of the cooling relative to the plastic melt flowing into the cavity is done with an on-timer and a delay-timer activated by the clamp close signal from the molding machine. At clamp close, the delay timer activates, to allow the user to place the “cooling on-time burst” anywhere in the overall cycle. The gray bars shown in the picture represent “mold open time.” This cooling energy can be tailored to provide an engineered cooling curve to match the heating curve of the incoming molded shot delivered by the machine. This heating/cooling thermal energy exchange matching is the core technology that distinguishes the iCool® from everyone else in the industry.

Unlike pulsed cooling valve technology that is limited to the pressures and temperatures available from the supply chiller, the precision timed delivery of cooling can be of any temperature, flow rate, and time duration desired by the user. With valve technology you have only cold water from the chilled supply to work with. Supply chillers can vary in pressure and flow due to the demands placed by changing molds and starting and stopping molding machines all the time. These variability’s are now eliminated with the iCool® because we control the temperature, flow velocity, and energy exchange rate with the mold and do so with high energy efficiency while increasing the flow rate 2 to 3 times over what is available with standard technology.

BoostMold™ as a new Passive Boosted Variotherm technology allows significantly higher flow rates of cooling to be applied to double the cooling rate in the mold compared to un-boosted flow. The thermal energy exchange rate with the mold is controlled with proprietary software control algorithms. It has been found that chilled water delivered in a timed duration can accelerate the rate of heat removal from the molded part over continuous warmer flow cooling. During the off flow time the residual heat from the cooling part to preheats the mold cavity steel for the next shot. The hot plastic preheating the mold cavity reduces melt flow lines, improves flow in long runs, allows fiber filled materials to be more homogenized, and reduces part warpage. The net result is that cycle reductions over 50% can be achieved with improved part quality along with huge electrical energy savings.

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