As a synthetic resin of thermoplastic polymer, the polyethylene terephthalate, PET in short, has been globally accepted to be the ideal medium for packaging a wide range of edible and non-edible items. This in turn has created an unprecedented demand for the products and services rendered by the manufacturers of PET blow moulding (spelt as molding in the US) and extrusion systems.
Thus the PET preform hot runner moulds industry plays a pivotal role in catering to the needs of the packaging segment of consumer goods. The concept of hot runner system is based on a heated manifold and a number of heated nozzles. The manifold distributes the plastic entering the mould to the different nozzles which then are calibrated and precisely injected into the points of the cavities.
The initial hot runner systems designed and developed during the 1960s showed adverse effects. Fortunately, the polymer scientists and engineers designing and manufacturing the PET blow moulding machines gradually resolved these problems. And by the 80s and 90s this technology proved its advantages to the packaging industry, the bottling segment in particular. This aspect could be gauged from the fact that the USA witnessed the number of plastic containers for the soft drinks shooting up within a span of 22 years (1977-1999) from a mere zero to ten billion pieces!!
Externally heated and internally heated are the two main versions of hot runner system. In the externally heated type, molten plastic runs within a solid manifold including the nozzles. However, it was not so in the now obsolete internally heated type where the plastic flow was directly over slender heaters inside oversized runners.
The three modes of operation in a hot runner system are:
Mold open cycle
Part ejection cycle
The temperature is regulated and controlled in a hot runner system which enables consistency in the overall operation. The moulds used in hot runner system are comparatively dearer in terms of manufacturing cost but in the long run, they are beneficial as evident from the drastic reduction of plastic waste and the time spent in recycling such unwanted or excessive materials.
However, a cold runner is based on a channel formed between the two halves of the mould to carry plastic from the injection moulding machine nozzle to the cavities. Each time the mould opens to eject newly formed plastic parts good amount of material from the runner is also ejected causing ample wastage which is not so in a hot runner system.
Incidentally, the blow moulds manufacturer in India has made a mark for quality products and services of moulds and systems both on the domestic and international fronts. These conform to prescribed quality parameters and ISO specifications covering:
Wall Thickness Test
Neck Finish Test
Visual and Automatic Control
Intrinsic Viscosity (IV)
Indeed, reputed Indian companies have excelled in designing and manufacturing a wide range products with differing capacities like PET stretch blow moulding, extrusion blow moulding, reheated stretch blow moulding (RSBM) to injection stretch blow moulding (ISBM) systems.
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