The poor thermal conductivity of plastics materials leads inevitably to a long cooling phase in blow moulding. To counter this there are various super-cooling processes, such as liquid gas cooling with nitrogen or carbon dioxide. These methods are said to be efficient, but it is not well-documented whether, and in what way, the harsh and abrupt cooling negatively affects the quality of the product, what tensions are created in the product by uneven cooling, and whether increased productivity does not demand too high a price in ecological and economic terms.
Compressed air, on the other hand, is found in every blow moulding operation, but is still not well-appreciated as a cooling medium. The reasons may be the assumption that the production of compressed air is very expensive and that compressed air does not have the necessary cooling qualities to make a significant difference. But what would be more logical than to use the available means of production and to unleash a blizzard inside the product with little additional cost and effort?
Before we look at intensified internal cooling we must determine where the critical points in our …
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