1. Flash at the bottle neck: This refers to a thin, raised layer of material forming at the neck threads or the mold parting line. It is typically caused by mold wear leading to imprecise mold closure, resulting in excessive material injection and the formation of flash.
2. Poor mold closure: This includes issues with both the preform mold closure and the blow molding mold closure. Like neck flash, the root cause is usually mold wear.
3. Excess material at the shoulder: This appears as a ring-like protrusion around the bottle shoulder. It is generally caused by uneven heating/rotation or uneven material stretching during the blow molding process.
4. Impurities inside the bottle: These include black specks, foreign objects, and undissolved resin particles. Causes usually stem from issues with material processing prior to injection molding. For example, a dirty mold can cause black specks; impure resin pellets can introduce foreign objects or incomplete melting; and a failed filter screen at the distributor nozzle allows incompletely plasticized particles to enter the mold cavity, resulting in undissolved particles in the finished bottle.
5. Color issues: This applies to colored bottles (e.g., light green for green tea bottles). It is important to monitor whether the color is normal. Color intensity falls within a specific range, usually assessed visually; deviations outside this range indicate an abnormality. Such abnormalities are typically caused by malfunctions in the color dosing unit or issues during screw rotation and mixing.
6. Off-center base: This occurs when the injection point does not align with the center of the blow-molded bottle, resulting in uneven wall thickness. There are several common causes: first, the injection mold itself may be defective, leading to uneven preform wall thickness; second, uneven heating of the preform during the heating process can cause uneven stretching; and third, the stretch rod may tilt as it descends during blow molding.
7. Fluorescence: Often appearing alongside an off-center base, this phenomenon occurs when the bottle wall is too thin; under lighting, certain areas appear whitish and shiny. The causes of fluorescence are similar to those of an off-center base. ...often appear at the bottom and shoulder of the bottle; excessive air-blowing pressure can sometimes also cause fluorescence.
8. Air bubbles inside the bottle. The primary cause is insufficient drying, resulting in gas being trapped within the plasticized material.
9. The bottle may also exhibit phenomena such as whitening, opacity, and upward curling of the reinforcement ring.