During the production of a new mold, mold design is the most important point.
The shape of the molded part, the time involved in making the mold, have a direct impact on the cycle time of the molding. For example, undercuts and deep threads often require a separate moving part, which increases the cycle time of each molding operation.
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Angles in the side walls are required to allow the mold to be removed from the mold.
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The surface quality of the molding must be decided before the mold is completed. Embossing, etching, and other finishes can be added to the molding to enhance the molding’s aesthetic qualities. Any imperfections in the finish of the molding will permeate every mold made.
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The weight, surface area and thickness of the molding directly affect the cycle time. In cases where dies have significantly varying thicknesses, cooling must be controlled very carefully, otherwise depressions (sinking marks) will form on the outer surface of the die due to excessive shrinkage of the thick section of the die.
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The number of cavities in a die is determined by the number of units required. The number of cavities directly affects the machine size required for the multi-cavity die; which affects the cost of the mold and the unit cost of the molding. Where there are many cavities, each must be relative to the others, and the cooling profile must ensure equal cooling of the outer and inner cavities, otherwise molds of different sizes will form. Hot runner systems are generally used for multi-cavity systems. This reduces cycle time and the amount of waste material generated, but increases the overall cost of the molds.
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The need to add inserts or labels during the molding sequence should be considered at the mold design stage.
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All injection molds require a point or points into which molten plastic is introduced. If not taken into account at the design stage, this can leave unsightly surface imperfections on the finished mold that require a further step to remove them and incur extra cost.
