The preform and its heating, pre-blowing (position, pressure and flow), stretching rod, high-pressure blowing (pressure, position) and mold are factors that affect the bottle making process of the bottle blowing machine.

1. Preform

Preforms, also known as parisons, are injection molded of PET pellets. It requires that the proportion of recycled materials should not exceed 10%, and the number of recyclings cannot exceed two. The preforms after injection molding or preforms used after heating are cooled for more than 48h, and the preforms used should not be stored for more than 6 months. Different production dates, especially preforms with too long intervals cannot be mixed, the main reason is that the bottles The raw materials used in the preform, the proportion of secondary materials mixed and the residual stress in the preform are different, and these factors have a significant impact on the blow molding process, and should be treated according to the actual situation.

2. Heating

The heating of the preform is completed by the heating furnace, which is manually set and automatically adjusted. The height of the heating furnace should be about 25mm, about 19.6mm away from the conveyor wheel. The preforms continuously run through the entire oven on the conveyor wheel, so that the preforms are heated more evenly and can be shaped well, which overcomes the shortcomings of uneven heating caused by static preheating and manual rotation of the preforms. However, improper adjustment of the heating furnace will cause uneven distribution of the wall thickness of the bottle being blown up and down (such as light weight and heavy weight), the bottle mouth becomes larger and exceeds the standard, and the product defects such as hard neck, and even cause torque failure of mechanical parts. The temperature of each area can be adjusted according to the molding conditions of the product, and the opening of the oven lamp must be considered. In addition, the setting of the oven output power also has a great influence on the heating of the preform, which controls the heat output of the entire oven. When the machine is not turned on for a long time, when it is turned on again, the initial output power should be set higher accordingly, and then gradually reduced to the normal state during the normal production process. The output power is generally about 80%, especially when the ambient temperature is below 5 ℃, The effect is significant.

Theoretical output of Taizhou dianya high speed 8 Cavity Full Automatic Servo Blow Molding Machine capacity 9000-10000 BPH.

The production process of bottle blowing is also related to the ambient temperature of the production. The ambient temperature is generally room temperature (about 22°C). If the temperature is too high, the product is prone to coagulation point agglomeration; the temperature is too low, the product performance is unstable when the machine is started, and the specific operation should be adjusted according to the actual situation and experience.

3. Pre-blow

The role of pre-blowing in the blowing process is to give the preform a shape, and at the same time, the longitudinal strength of the pre-stretching rod is increased by longitudinal stretching. The whole process is that the pre-blowing cam pushes the three-way valve to the pre-blowing position during the bottle blowing process, and is completed by the one-way valve. Pre-blowing position, pressure and flow can all affect the quality of the bottle.

Position: The pre-blowing position is advanced, there will be deflection and thinning of the bottom of the bottle, uneven foot wall thickness and white, light weight on the top and bottom, hard neck, even bottom penetration and other defects; after the pre-blowing position is wrong, then There will be defects such as light weight, heavy weight, thickened dots, and depressions.

Air flow The pre-blowing air flow is controlled by a check valve, which is generally suitable for 3-4 turns. The air flow is large, the bottom is heavy, the points are thin and partial, the feet are whitish, and the wall thickness is uneven; the air flow is small, the points become thick, and the segmented pieces are overweight.

Pressure: The pre-blowing pressure is preferably 0.8-1MPa. When the pressure is high, it may cause light up and down, point deflection, uneven foot wall thickness, whitening, etc.; when the pressure is low, it cannot be fully stretched, the bottom is heavy, and the point is thick.

The forming conditions of the feet and points of the bottle have a great influence on the quality of the bottle. Improper adjustment often causes fatal defects such as bottle burst (under normal experimental conditions) and leakage.

4. Stretching rod

The stretching rod is a device that stretches the heated preform while pre-blowing with the cooperation of pre-blowing air. It is reset after high-pressure blowing and before venting. The stretch rod can move vertically and smoothly during the bottle blowing process. The driving pressure is 0.55-0.8MPa, and the gap with the bottom mold is 2.3-2.5mm, which is the thickness of the preform 1/3-1/2. If the gap is too large, the bottom point of the bottle will be shifted; if the gap is too small, the point will become thinner.

5. High-pressure blowing

The function of high-pressure blowing is to make the molten material fully stretched, close to the mold wall, so that the bottle is fully formed, and at the same time, it is stretched laterally to improve its lateral strength. The main influencing factors are location and pressure.

The high-pressure blowing pressure is generally 3.7-4MPa, which is determined by its molding characteristics and the nature of the filled beverage (carbon dioxide). There are two positions, that is, the position of high-pressure gas and the position of exhaust. The time between the two is the pressure holding time during molding. The length of this period has a great impact on the stability of the bottle capacity. Insufficient high-pressure gas can easily cause improper bottle formation and insufficient foot blowing.

6. Mould

Mold is one of the important factors affecting bottle blowing. The bottle body is a half mold, and the bottom of the bottle is independent, which is a typical blow molding mold. During the production process, keep the mold at a constant temperature, clean, and vent holes.

When the mold heating and cooling system fails, there will be defects such as bottleneck distortion, bottle tilt, volume and height changes, and the bottom becomes heavier; maintaining mold temperature can also prevent condensation on the mold surface.

After PET molding, the shrinkage rate is relatively large, generally 1.8%, and it is slightly reduced after adding glass fiber reinforcement, but it still reaches 0.2%-1.0%. In general, the shrinkage rate of high mold temperature is large and the shrinkage rate of low mold temperature is small. In order to maintain the stability of the volume of PET bottles, the mold temperature should be strictly controlled. Generally, the temperature of the bottle is slightly higher at 20-45℃, and the bottom is lower at 6-15℃. High bottom temperature will make the bottom heavier and thicker.