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Blow Molding

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PET Resin
Preform molding
Preform design
Preform Animation
Blow Molding
Bottle Design
Reheat stretch blow machinery
Single stage machinery
One stage vs. two stage machinery

 

For both one-stage and two-stage blow molding processes, a hot preform is clamped in a blow mold. A stretch rod is usually used to stretch the preform to the base of the mold, while low pressure compressed air is used to “pre-blow” the preform into a bubble. Then high pressure air is applied to push the PET bubble into all the details of the blow mold, and to cool the newly-made bottle. Time is allotted in the cycle to depressurize the mold before opening it and removing the bottle.

The little graphic above is a reasonable but not exact representation of how the preform inflates.

Important factors to make high-quality bottles at good production rates include:

  • The right preform and bottle designs
  • The right grade of PET resin
  • Good injection molding practices, to make high-quality preforms
  • The correct temperature profile of the preform before blow molding
  • The correct timing for stretch, pre-blow and blow
  • Equipment and molds in good operating condition
  • Adequate auxiliary services such as compressed air and chilled water