Single Stage Blow Machinery

Start
PET Resin
Preform molding
Preform design
Preform Animation
Blow Molding
Bottle Design
Reheat stretch blow machinery
Single stage machinery
One stage vs. two stage machinery

These machines consist of an extruder, a vertically moving injection assembly, a horizontally moving blow assembly, and an ejector station where the bottles drop into a chute. Some machines also feature a conditioning station.
 
The material is plasticized in the extruder and injected into a hot runner system, which is usually thermo-gated. This means that there is a thermal cut-off of the cold preform from the hot melt channel. On some machines, the hot runner moves up and down with the cavity and the extruder has to disengage from the so-called sprue-bushing of the hot runner, while on others both cores and neck splits move vertically up so that the hot runner stays stationary. This latter method is the preferred one since disengaging the extruder leads to drool and possible contamination.
 
The injection station is very similar to the standard injection molding machine. Differences are that the molded preforms stay in the neck splits and the vertical movement of the injection clamp whereas most injection molding machines for preforms move horizontally.
 
In machines with conditioning station, a suitable shaped, temperature controlled Aluminum rod is inserted into the preform. Areas that touch the preform cool it down. These colder areas become stronger and can pull weaker areas of the preform into the far corners of the blow mold. For example, an oval bottle is conditioned by cooling down the two sides of the preform that will form the far corners of the bottle. On the outside of the preform, section heaters control the axial temperature profile of the preform.
 
In machines without conditioning station, the injection mold cooling is sometimes split into several areas that are controlled with individual chiller modules, achieving similar results than the conditioning station. Some companies use oval preforms.
 
All blow stations move horizontally. The neck split plates move into the blow mold area with the warm preforms attached and the preforms are stretched and blown. During the next cycle, they move to the ejector station where they are either dropped into a chute or picked up by a robotic arm and placed on a conveyor belt.
 
Advantages of the single stage process are:

• high flexibility
• lower capital cost for the entire system
• higher thermal efficiency because the plastic is only partly cooled down
• neck ring support not necessary since the preforms stay in the neck splits
• preforms are not damaged before blowing resulting in scratch-free bottles
• neck and bottle are always oriented

 
Disadvantages are:

• each injection cavity requires one blow mold cavity
• output limited
• higher capital and mold cost compared to reheat stretch blow molders that buy preforms
• axial heat profiling limited

 
Manufacturers are: Aoki, Automa, Gerosa, Golfang, Nissei ASB