Posts Tagged ‘PP containers’

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

Wednesday, April 7th, 2010

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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Blow Molding Process Comparison: Shuttles (Continuous Extrusion)

Wednesday, April 7th, 2010

Shuttle Machinery – Extrusion Blow Molding

This is the most popular type of machinery for blow molding high density polyethylene (HDPE) and Polypropylene Plastic (PP) containers around the world. Literally thousands are sold every year. A shuttle machine consists of either single or dual clamps that shuttle (or slide) from under the die head to a blow pin assembly for blowing. The machines come in all sizes and configurations from single cavity to as many as 20-30 and bottle sizes from a few ounces up to a 10 litre jerry can. Included in the shuttle group is the long stroke type blow molding machine. Popular manufacturers include Bekum, SIG, Automa and Magic to name only a few of hundreds.

PROS:

  • Relatively inexpensive for small to medium volume production requirements
  • Deliveries container with calibrated neck
  • Typically trims container prior to exiting machine
  • Most flexible in container size and number of cavities
  • Can handle coextrusion
  • Can handle all type of container shapes including handleware

CONS:

  • Can not process PET material
  • Hydraulics and controls can be complex
  • Requires multiple machines for very high production volumes unless
  • Multiple parisons can be difficult to process consistently

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