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03-11-2008

Target Cooling of Hot Spots

Evaporative cooling is especially well-suited for cooling small diameter cores and ejector pins

Evaporative cooling is especially well-suited for cooling small diameter cores and ejector pins

Many processors are confronted with poorly accessible hot problems zones, so–called "hot spots", in injection molds. A system that provides a high cooling capacity in very tight spaces promises a remedy. Relatively large amounts of heat are needed to vaporize a liquid. A new cooling system that makes use of this effect has been developed by Stemke Kunststofftechnik GmbH, Döbeln. High cooling capacities can be achieved in very small cooling channels with very small amounts of liquid on the basis of vaporization. Cooling channels with a diameter of less than 2mm are large enough to cool very small diameter cores to any specific temperature.

Until now, evaporative cooling was based on allowing liquid CO2 to reach the hot spots via capillaries, where it vaporized at the end of the tube in a defined expansion chamber. The amount of coolant required in this case is relatively large, because the vaporized CO2 is released into the surroundings. By using the refrigerant R404a, evaporative cooling can now be employed in a closed loop. The vaporized refrigerant is liquefied in a chiller outside the mold, and is once again available for cooling.

To control the cooling process, the temperatures of all relevant cooling zones in the mold are measured. Temperature sensors positioned closed to the surface transmit the actual temperature values to a controller that compares the actual values with the setpoints, and then converts this information into appropriate injection pulses for the refrigerant. In this way, the temperatures in the various mold zones can be controlled exactly.

The cooling system has been on the market since the beginning of 2007 and is already in use at a number of well-known companies. The range of applications extends from very small molds for writing instruments to large molds in the automotive industry, e.g. for production of instrument panels and bumpers.

Dr.-Ing. Harald Sambale
sambale <AT> kunststoffe.de

contact
Stemke Kunststofftechnik GmbH
Waldheimer Straße1
DE 04720 Döbeln
Tel: +49 3431 6637-0
Fax: +49 3431 6637-60

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