Posts Tagged ‘High Volume’

Blow Molding Process Comparison: Wheels (Continuous Extrusion)

Wednesday, April 7th, 2010

Rotary Wheel Blow Molding Machinery

The rotary wheel blow molding machines are the machine of choice for very high volumes of containers for markets such as liquid detergent and juice in North American markets. Wheels are typically chosen over shuttles because of processing ease (and cost) due to single parison technology and lower cost per container for high-volume applications. This is especially true for coextrusion and multilayer applications. Machines can be designed to handle a wide range of container sizes, but are typically committed to a narrow range of container variation after built. Because the containers are blow with a needle (instead of blow pin), it is not unusual to blow containers in a neck to neck configuration to increase the production output. Wheels come in various configurations including indexing, continuous motion, vertical (like a ferris wheel) and horizontal (like a merry go round). Some even now have the capability to produce calibrated neck containers, such as a reciprocating screw (Intermittent extrusion). Most, however, rely on downstream trimming equipment to trim and finish the container.

PROS:

  • Lowest cost method for high volume production requirements
  • Simple design and controls for maintenance
  • Single parison well suited for multilayer application for repeatability and cost
  • Easy to utilize IML
  • Can achieve very high production volume from a single machine

CONS:

  • Typically can not be converted to different number of cavities after being built
  • High investment requires commitment to high volume production situations
  • Requires secondary trimming and finishing equipment

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

Wednesday, April 7th, 2010

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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