Blow Molding Process Comparison: Reheat Stretch Blow (2 Step)

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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