Blow Molding Process Comparison: Injection Stretch Blow (1 Step)

April 7, 2010
|In Blow Molding, Injection Molding
|By admin

Injection Stretch Blow (1-Step)

This process is almost entirely dedicated to PET and more recently, PP applications. The process is very similar to Injection Blow except for two areas: 1) the preforms are not transported on core rods but instead held by the neck finish and 2) during the blowing process, rods stretch the preform prior to blowing to orient the material. For materials such as PET this biaxial orientation substantially increases the physical properties to weight ratios. Major manufacturers include Aoki and Nissei.

PROS:

  • Scrapless process meaning no flash to trim and no regrind
  • Allows for biaxial orientation for strength and clarity
  • High quality injection molded neck finish
  • Typically suited for .5 litre up to 20 litre
  • Capable of PET non-carbonated beverage containers
  • Capable of lower volume production applications
  • Does not require separate preform mold and machine

CONS:

  • High tooling cost
  • Minimum cycle typically 18-20 seconds
  • Can not produce carbonated beverage containers (Not enough biaxial orientation due to high preform temperature at blowing)
  • Not suited for polyolefins
  • Can not blow handleware
  • Difficult to run coinjection or multilayer

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