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 described above 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
Injection Stretch Blow (2-Step)
This process is also almost 100% for PET applications. The processes utilizes preforms made on a stand-alone injection molding machine, stored and then reheated and stretch blow similar to the 1-step process above. Here, however, the preforms are blown at a lower temperature allowing the maximum amount of biaxial orientation and therefore the maximum strength to weight ratios. The reheat process can be for ultra high output type applications such as carbonated soda bottles while other machines can be smaller for medium to high production requirements. Major machinery manufactures include Sidel and Krupps.
PROS:
- Can be very high speed production (40,000 containers / hour)
- Produces a very high strength-to-weight ratio container
- Can purchase or make preforms
- Primarily PET material
- Machines for low and medium volume application are becoming available
CONS:
- Can not mold handleware
- Not capable of polyolefins
- Must have a separate preform mold and injection molding machine or purchase preforms
- For low volume production, if special design preform is required, cost can be expensive
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