Jar Preform mould produces the thick-walled plastic preform that later expands into a wide-mouth jar through stretch-blow moulding. The tool contains a set of cavities and cores sized for the larger neck diameter typical of jars. Molten PET enters under pressure, fills each cavity completely, and takes on the exact shape of the moulded surfaces, including the finished thread and sealing face. After cooling, the Jar Preform mould opens and the rigid preforms are ejected for collection.

Cavity geometry receives close attention because jar preforms carry more material in the neck and shoulder areas than bottle preforms. The cores form the internal diameter while the cavities define the outer profile and wall thickness. Jar Preform mould that holds precise alignment between core and cavity delivers preforms with even material distribution, which supports uniform stretching when the preform is later reheated and blown. Polished cavity surfaces help the plastic release cleanly and leave a smooth exterior.

Cooling circuits run through both the cores and the cavity plates. Water flows close to the plastic so heat leaves the part quickly and evenly. Rapid, balanced cooling shortens the cycle and reduces internal stress that could distort the neck finish. Jar Preform mould designers place these channels to keep temperature differences small across the thick neck region and the thinner body section. Stable mould temperature also helps the threads hold their exact pitch and profile.

The neck finish is fully formed inside the tool. Support rings, threads, and the sealing surface are machined into the cavity inserts so every preform leaves with a ready-to-use closure interface. Gate location is chosen to fill the larger volume of a jar preform without creating excessive residual stress or a bulky vestige. Hot-runner systems keep the plastic at the correct temperature as it travels to each cavity.

Wall-thickness control remains central to performance. Sensors and process data help operators maintain the target weight and material distribution. When the cavities fill completely and the cooling system removes heat at the designed rate, the Jar Preform mould produces preforms that match one another in length, neck dimensions, and overall mass. These preforms then move forward to conditioning and blowing, where they take on the final jar shape.