Injection is the process used for manufacturing preforms. It requires an injection machine with its respective molds, to transform resin pellets into the desired shape (in this case the preform).
However, injection molds have a higher degree of complexity than blow molds. Typically, injection molds are made up of Cold Half and Hot Runner. The Hot Runner is the one that distributes the material to the Cold Half by means of heated pipes with electrical resistances that ease the fluidity of the material. The Cold Half, on the other hand, is where the preforms are finally formed. It has built in cooling circuits (air / water) that help solidify the resin, reducing cycle time and increasing production per hour.
Each Cold Half consists of a determined amount of Stacks. The Stacks are not standard, but are usually made up of the following parts:
- Core
- Core cooling tube
- Lock rings
- Neck rings
- Cavity flange
- Cavity
- Gate insert
At PET Packaging Network, we work closely with PETform, a company specialized in the manufacture of this type of molds.
PETform is an Indian company with more than 15 years experience, which offers injection molds, Hot Runner systems and spare parts. The company also offers prototyping, preform design, and small scale production.
Through them, we can offer complete injection molds for preforms, conversions kits (lightweighting, changing cores, neck rings or cavities) and refurbishments (reconditioned of molds, replacement of worn or broken pieces).
PETform shows a strong commitment towards innovation, and offers their own developments:
- Injection system for preforms with 6-12 mm wall thickness, in which the preforms leave the mold cavity but stay on the core set for a whole cycle, before being transferred to a cooling tube, where they stay for another two cycles. With this system, which can be fitted to any standard injection machine, the cycle time can be significantly reduced.
- Hot Runner system with dynamic sealing, which permits an operating temperature range of 180ºC all the way up to 350ºC allowing the use of the same hot runner for moulding both PP and PET preforms.
- Molds for preforms with conical bases, to reduce material stagnation at the bottom center of the bottle and allow for faster cooling and lower gate crystallinity during injection moulding.
