The preform's structural design directly impacts the quality of the blow-molded bottle. Key components include:
The neck: This part, with its threads (for sealing with the bottle cap), requires the highest precision, ensuring perfect compatibility with the cap (e.g., thread dimension tolerance within ±0.02mm).
The bottle body: This part is tubular and has a uniform wall thickness (deviation ≤0.1mm). Otherwise, problems such as uneven thickness and deformation may occur during blow molding.
The bottom: This part is closed, typically designed as a hemispherical or flat bottom. It must be strong enough to withstand the tensile forces of blow molding.
Key parameters include:
Weight: This part must be within ±1% tolerance. Excessive weight increases costs, while excessive lightness compromises bottle strength.
Perpendicularity: The perpendicularity between the neck and the bottle body must be within 0.5mm/m, otherwise, the bottle may become misaligned during blow molding. Crystallinity: The crystallinity of the preform after injection molding needs to be moderate (about 10%-15%). Too high a crystallinity will make it difficult to stretch during blow molding, while too low a crystallinity will make the preform easily deformed.