Posted: 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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Tags: PET, PP containers
Posted in Blow Molding, Structural Plastics / Injection Blow | 1 Comment »
Posted: 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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Tags: HDPE containers, High Density Polyethylene, Polypropylene Plastic, PP containers
Posted in Blow Molding | 1 Comment »
Posted: April 7th, 2010
Injection Blow Machinery
These machines inject mold a preform onto core rods and then index the core rods to a blow station to blow the container. Machines are typically 3-4 stations to allow for condition and part removal. They are utilized extensively for very small containers such as pharmaceutical and hotel shampoo type containers. Major manufacturers are Jomar, Procrea and Milacron.
PROS:
- Scrapless process meaning no flash to trim and no regrind
- Typically suited for containers .5 litre and smaller
- Capable of running a wide range of materials
- High quality injection molded neck finish
CONS:
- Very high tooling cost per container typically cost 40-50% of the machine cost
- Difficult to run coinjection or multilayer
- Minimum cycle time typically 15 seconds
- Can not do handleware
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Tags: Hotel Shampoo Containers, Pharmaceutical
Posted in Blow Molding, Structural Plastics / Injection Blow | 1 Comment »
Posted: 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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Tags: High Volume, PET
Posted in Blow Molding, Structural Plastics / Injection Blow | 1 Comment »
Posted: April 7th, 2010
Reciprocating Screw (Intermittent Extrusion)
This is the most popular and cost effective method to produce lightweight dairy, juice and water containers. In this process the extruder feed screw reciprocates similar to an injection molding machine. The molds are stationary under the die head and simply open and close but do not shuttle. As the screw moves forward, the parison is pushed out into the molds for blowing. For lightweight containers, cycle times can be very fast with some under 5 seconds. Major machinery manufactures include Rocheleau and Uniloy.
PROS:
- Very fast cycle time capabilities
- Simple machine motions since clamps do not move
- Capable of 16 cavities small bottles or 8 gallons. Smaller models available
- Relative low cost per cavity
- Can easily run homo polymers and very low melt temperatures
CONS:
- Limited to monolayer applications
- Primary materials are HDPE and limited amount of PP
- Difficult to parison program
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Tags: Dairy Containers
Posted in Blow Molding | 2 Comments »
