PET Preform Injection Mold Technology Knowledge

STAVAX S420 or S136 stainless steel (HRC 55±2) is used for cavities/core pins, with a service life of 800,000 to 1,200,000 cycles. Pharmaceutical-grade molds require special steel certified by USP Class VI, with cleanliness meeting ISO Class 5 standards, and their unit price is 2-3 times that of ordinary beverage molds. DIN 1.2311 steel is mostly used for mold bases, with a thickness tolerance controlled within 0.015mm after precision grinding.

High-end molds are equipped with needle-valve hot runners with German heating elements, achieving temperature control accuracy of ±1℃ and uniform melt distribution. To address the easy degradation of recycled PET (rPET), the flow channel curvature and heating power of the hot runner need to be optimized to reduce material residence time.

3D-printed conformal cooling channels have replaced traditional drilled channels. These channels fit perfectly with the contour of the cavity, improving cooling efficiency by 30%-60% and shortening the molding cycle to within 15 seconds. For key parts like preform necks, W-shaped cooling channels increase the cooling area by 40%, effectively avoiding defects such as neck deformation.

Mold cavitation has upgraded from the traditional 8-16 cavities to 32, 64, and even 144 cavities. Combined with high-speed injection molding machines, production capacity can be doubled, and unit costs reduced by 12%-18%. CAE mold flow analysis is required to ensure the filling pressure deviation of each cavity is ≤5%.

 The tolerance of preform neck threads is controlled within ±0.02mm, and 100% inspection is conducted using CNC precision machining and coordinate measuring machines. The wall thickness deviation is ≤5%. For food-grade molds, the acetaldehyde content is controlled within ≤5ppm.