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Mold Selection P3

Selection of an Appropriate Mold Because of the better cooling, the, mold will cycle faster for higher productivity Interchangeability of components is easier to achieve and repairs are less costly. Heat expansion is not a problem; by having the cores mounted to float a limited amount to self-align with the cavities, regardless of any temperature difference between the plates, the size of the mold (number of cavities) is not limited. If this design is used for molding products that can only be ejected with air, it becomes a really simple mold, with very few mold shoe components. This method is of. | previous page Copyrighted Materials 1 Copyright 2006 Hanser Publishers Retrieved from www.knovel.com I 4.1 Selection of an Appropriate Mold-------------------------------- 137 Because of the better cooling the mold will cycle faster for higher productivity Interchangeability of components is easier to achieve and repairs are less costly. Heat expansion is not a problem by having the cores mounted to float a limited amount to self-align with the cavities regardless of any temperature difference between the plates the size of the mold number of cavities is not limited. If this design is used for molding products that can only be ejected with air it becomes a really simple mold with very few mold shoe components. This method is of special advantage in stack molds which are then much simpler. Today most molds for small containers dairy etc. are of modular construction Disadvantages of the modular mold design are The cavity spacing is larger than a comparable retainer plate design because the wall thickness of the cavity must be strong enough to withstand the injection pressures. Therefore the mold will be larger for the same number of cavities and more expensive. Because the mold will be larger than a comparable mold with retainer plate design the cost of the mold will be somewhat higher but this additional cost can be easily recovered by the increased productivity and lower maintenance cost. Modular molds cannot be used for 2-plate molds because the cold runners would be interrupted between the modules. However they can be used for 3-plate molds. 138 4 Mold Selection N G--------- k 0 F K A B C O M A E L H I Figure 4.49 Modular 6-cavity mold Courtesy Husky R Figure 4.50 Underside of core backing plate Courtesy Husky Figure 4.49 shows a modular 6-cavity mold for a container with core lock design. The cavities A are set into the cavity retainer plate B the hot runner system is in the plate C behind the cavities. In front is a cavity A with cavity bottom E . The core .