Problems with the use of hollow blow molding opportunities

Problems with the use of hollow blow molding opportunities

The blow molding process of the hollow blow molding machine is a two-way stretching process. Common problems and solutions for blow molding of the hollow blow molding machine are to reduce the temperature of the preform, accelerate the stretching speed, check the open space between the tie rod head and the bottom mold, and delay the pre-blowing. , Reduce the pre-blowing pressure and delay the high-pressure blowing.

The blow molding process of the hollow blow molding machine is a two-way stretching process. In this process, the PET chain is extended, oriented and placed in two directions, and then the mechanical properties of the bottle wall are increased, and the stretching, tensile and impact resistance are improved. Strength and good air tightness. Although stretching helps to improve the strength, it should not be over-stretched. It is necessary to control the stretch-inflation ratio: do not exceed 3.5~4.2 in the radial direction, and do not exceed 2.8~3.1 in the axial direction. The wall thickness of the preform should not exceed 4.5mm. .

Bottle blowing is carried out between the glass transition temperature and the crystallization temperature, generally controlled between 90 and 120 degrees. In this interval, PET behaves in a highly elastic state, and it becomes a transparent mold after rapid blow molding and cooling and setting. In the one-step method, this temperature is determined by the length of the cooling time in the injection molding process (such as the Aoki hollow blow molding machine), so it is necessary to connect the injection-blowing station.

The blow molding process of the hollow blow molding machine includes: stretch-blow once-blow twice. The three actions are very short, but they must be well coordinated, especially the first two steps determine the overall distribution of the material and the quality of the blown bottle. Good or bad.

Therefore, it is necessary to adjust: stretching start time, stretching speed, pre-blowing start and end opportunities, pre-blowing pressure, pre-blowing flow, etc., if possible, it is best to control the temperature distribution of the entire preform, inside the preform The temperature gradient of the outer wall. During the rapid blow molding and cooling process, induced stress is generated in the bottle wall. For gas-filled beverage bottles, it can resist internal pressure and has advantages, but for hot-filled bottles, it is necessary to ensure that it is fully released above the glass transition temperature.