Temperature Control Technology
Mold temperature is one of the most important injection molding parameters since it decisively influences the cycle time as well as the dimensional tolerance. The new cooling elements with their novel connecting mechanism from Wema GmbH, Lüdenscheid, Germany, are a cost effective solution for constructing a high performance cooling system. These make conventional thread cutting a thing of the past. The holes for the temperature control connections are simple and quick to prepare using standardized tooling. Regardless of whether it is a quick coupling, elements for core cooling, diverter and closure plugs, all the connections are made using the same technique. Unlike all the previous systems on the market the new one does not require connecting nipples. Particularly advantageous for the plastics processor is the fact that the protruding nipples cannot be damaged or broken off during transport and storage. Cost benefits result from the elimination of these components and the operations required to install them.
All the temperature control connections are equipped with an identical patented attachment system. An elastic metal ring provides a secure attachment in the hole whilst an additional Viton O-ring guarantees the necessary seal. The previous nipple/connector temperature control systems can be retro-fitted for the new concept by screwing an adaptor into the existing thread.
Cooling circuits in injection molding tools have to follow the contours as closely as possible. That can only be achieved by drilling several holes often running at various angles to each other. Diverter plugs secure the desired direction of flow for the temperature control medium. Particularly for very deep positions within the tool it was often a problem to attach the plugs densely and accurately. Depending on their size the new diverter plugs can be placed to accuracies of one millimeter in non-countersunk holes at depths of up to 1,900 mm. Plugs are available for hole diameters from 8 to 25mm.
In general a good core cooling is more important than the cavity cooling, since due to shrinkage molded parts have the tendency to contract onto the core. If several cores in a tool have to be cooled simultaneously there are two possibilities. In serial cooling the cooling medium flows through the cores one after the other. The effectiveness of the cooling is dependent on the length of the cooling path. Since the temperature of the cooling medium rises with increasing length a uniform cooling of the various cores cannot be guaranteed. With long cooling paths working with parallel cooling is therefore to be recommended. All the cores are uniformly supplied via a common manifold with an evenly cooled medium which is removed via a further cooling channel. In this way a constant cooling of all the cores can be achieved.
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