PET preform injection molding system with vertical clamping device

Hot filling of beverages places particularly high demands on the quality of PET preforms. The vertical technology used by KraussMaffei's preform injection molding system for the first time enables the production of hot-filled preforms with mold cavities of more than 48 dies.

Hot filling poses extreme requirements in terms of errors for PET preforms. Due to crystallization, particularly high precision is required during the production of hot-filled preforms, especially at the bottlenecks. Even very small temperature differences in the heating section of the mold can cause differences in the flow of the melt in the hot runner. Because of the different effects of shrinkage at the bottleneck position, elliptical deformation or bending may occur during the crystallization of the bottleneck position where the deviation is small.

Due to the high requirements, the empirical method that was previously applied is that the mold for hot filling preforms can be equipped with up to 48 cavities, since the best product quality can only be achieved without exceeding this number of cavity cavities. Especially when using horizontal machines, the heating coils that are superimposed on each other can create a chimney effect that causes difficult to control mold temperature fluctuations. This fluctuation of the mold temperature makes the melt flow properties in the respective cavities different, resulting in different material shrinkage properties.

The PET preform injection molding system has a vertical locking device. KraussMaffei has successfully overcome this obstacle. This is because the inevitable increase of heat in each heating coil does not affect the temperature distribution in the vertical mold. Therefore, when using a vertical mold, even if the number of cavities is greater than 48, high precision requirements for hot filled preforms can be satisfied.

The great demand for hot-filled preform products is first in the Asian market. In China and Thailand, KraussMaffei's PETForm system has been used to fill preforms with hot, 72-cavity or 96-cavity molds. This means that even in the production of challenging hot-filled preforms, the PETForm system achieves excellent production capacity.