The king of preform is that of 5-gallon (19-litre) bottle used in drinking water machines. It weighs between 650 and 750g. Even the disposable version weighs 400g. So the more popular moulds are single cavity based which allows the cold runner design.
At home, 3-gallon (12-litre) bottles are getting popular. Their preforms weigh between 300g and 520g. Their preform moulds could be 2-cavity based and use a hot plate or hot runner design.
The other number of cavities include 4, 6, 8, 12, 16, 24, 32, 48, 60, 72. To increase productivity, maximize on the number of cavities by using the clearance between tiebars, the platen dimensions and the injection weight of the injection molding machine to the most.
Most preform moulds are rectangular and are longer than they are wide. There are even injection molding machines dedicated to making preforms having a rectangular tiebar clearance to fit the needs of making preforms. The diagram shows the cavity layout for 32 cavities or fewer.
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