Miniaturized high performance cooling
Closed Circuit Hot Spot Cooling
If the cooling time in injection molding is overly long, it is often because difficult to reach hot zones, so called hot spots, cannot be efficiently cooled with a conventional mold cooling system. A new system from Stemke Kunststofftechnik GmbH, Döbeln, Germany, that is based on the same function principle as a fridge addresses exactly this area. A coolant circulates in a closed circuit between the injection mold and the refrigerating unit. The circulation of the coolant and therefore the mold cooling is controlled via a thermocouple.
The first mold worldwide completely without water and oil cooling, a joint project with 30 partners, was run a few weeks ago at EuroMold. A replica of a coral, whose geometry makes holes for conventional cooling channels impossible, was used as the demonstration part. Using the Stemke system holes with a diameter of less than 2mm are sufficient. In these holes a capillary is inserted the end of which acts as the nozzle for the liquid coolant. This vaporizes in the expansion space delivering its cooling effect. The gas flows back through the hole outside the capillary, is collected in a cladding tube and passed back via a magnet valve to the compressor of the refrigeration unit where it is re-liquified. The thermocouple sits at the end of the second hole.
Such tools will however for the present remain the exception. In the majority of cases reaching the hot spots will be the main issue. According to the manufacturer cycle time reductions of up to 30% are possible in this way. In a later edition of Kunststoffe the technique, for which Stemke won the central Germany IQ innovation prize in 2007, will be covered in full.
Stemke Kunststofftechnik GmbH
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