From 16 cavities to 72 cavities at 30 mm neck finish.
For 32-cavity and 48-cavity models (PET1400 and PET2100), we offer a dual-pump version to charge as the mould opens, closes and during ejection.
Holding pressure device is an option. It allows charging to start during the holding pressure stage.
Both features increase the time available for charging. AA (Acetaldehyde) level is reduced as the screw could turn slower without increasing cycle time.
PET preforms are intermediate products before bottles are made by a subsequent ‘reheat and blow moulding’ process (in a 2-stage process). Such bottles are now commonly used to hold mineral water, soft drinks, edible oil, etc.
The injection moulding process is used to make preforms so the neck is precise enough (vs the 1-stage extrusion blow moulding process) to avoid leakage. The production rate is much higher than the extrusion blow moulding process due to the high number of cavities. In 2020, 48-cavity moulds are popular in China for the mass production market.
The PET series of injection moulding machines was designed in 2000 to make preforms small and big, few and plentiful. There are 7 models in the series ranging from 16 to 96 cavities. Servomotor has been added to save energy during the long holding pressure time. The use of the Yuken ASR servomotor for the smallest 3 models are particularly significant in energy saving.
The number after PET designates its shot weight in PET in g. For example, PET680 and PET1000 are machine models with shot weights of 649 g and 958 g respectively.
There are two versions of PET1400 at different price points. The PET1400-S has a shorter screw at length to diameter ratio L/D = 24. The PET1400-620-S has L/D = 26. Furthermore, the latter’s clamping unit frame is more sturdy to take up a mould up to 32 cavities.
The second number after PET1400 is used to tell one version from the other. -620 means the horizontal clearance between tiebars is 620 mm although both versions have the same tiebar clearance.
Double-flighted compression section is used in all PET screws. This will improve the plasticizing capacity so no PET pellets remain in the preforms.
The PET2100-770-S can take a 48-cavity preform mould at 30 mm neck finish. We partner with Shini, a famous Taiwan brand, to provide the drying equipment to our customers.
Both the PET1400-620-S and PET2100-770-S have the dual-pump option to provide charging-on-the-fly, which means that charging also takes place during mould movement, ejection movement and robot arm movement. This will add charging time to the cycle without increasing cycle time. In a standard injection moulding cycle, charging can only take place during cooling time. Using this technology, 9.3 g preforms at 48-cavity could be produced in 12 s cycle time without out-of-the-mould cooling.
With dual-pump and holding pressure device options implemented, the whole cycle time except
for injection time can be used for charging.
Other than cycle time reduction, allowing more time in the cycle to charge can reduce the screw rotation speed. PET material degrades to AcetAldehyde (AA) due to long duration at high temperature in the barrel as well as high shear rate.
Reducing the rotational speed of the screw reduces the shear rate so that a low level of AA is generated in the preforms. Coca Cola has a stringent requirement on the AA level in PET preforms. Too high a level let AA migrate into the mineral water to give it a taste of petroleum.
The PET4200-920 can take a 96-cavity mould. It is so big that the clamping unit and the injection unit have to be separated for transportation in a container. It has also been used to make 5-gallon preforms in a 4-cavity mould. Please see the related video clip in the Tat Ming website.
The PET4400-S is our design of a pre-plasticizing unit. The pre-plasticizing unit can do charging-on-the-fly. The injection pot can also function as holding pressure device. This model can also take a 96-cavity mould.
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