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Factors affecting the production speed of bottle blowing mechanism

Bottle blank of automatic bottle blowing machine and its heating, pre-blowing (position, pressure and flow), stretching rod, high-pressure blowing (pressure and position) and mold are the factors that affect the bottle blowing machine to manufacture bottles in the process.
1. Bottle preform
Bottle preform, also known as parison, is formed by injection of PET pellets. It requires that the proportion of recycled materials should not exceed 10% and the number of recycled materials should not exceed two. The preform after injection molding or the preform after heating must be cooled for more than 48 hours, and the storage time of the preform used cannot exceed 6 months. Different consumption dates, especially the preform with long distance, cannot be mixed, mainly due to the different types of raw materials used for the preform, the proportion of mixed secondary materials and the residual stress in the preform. These factors have a serious impact on the molding process of bottle blowing, which should be viewed in detail according to the actual situation.
2. Heating
The heating of the bottle preform is completed by the heating furnace, which is manually set and automatically conditioned. The height of the heating furnace should be about 25mm, about 19.6mm from the escort wheel. The bottle preform runs continuously on the delivery wheel and passes through the whole oven, so that the bottle preform is heated more evenly and can be shaped better, which overcomes the defects of uneven heating caused by static heating and manual rotation of the bottle preform. However, if the heating furnace is not adjusted properly, it will cause uneven distribution of the wall thickness of the blown bottle (light as above and heavy as below), oversized bottle mouth, hard neck and other product defects, and even form the torsion problem of mechanical parts. The temperature of each area can be adjusted in detail according to the molding condition of the product, and the opening condition of the oven lamp tube should be considered at the same time. In addition, the setting of the oven output power also has a great impact 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 and is turned on again, the initial output power should be set higher, and then gradually reduced to the normal state during the normal consumption process. The output power is generally about 80%, especially when the ambient temperature is below 5 ℃, the effect is more significant.
There is also a certain relationship between the consumption process of bottle blowing and the consumption ambient temperature. The ambient temperature is generally room temperature (about 22 ℃). If the temperature is too high, the product is easy to show condensation point agglomeration; The temperature is too low, and the product performance is unstable when the machine is started. The detailed operation should be adjusted according to the practice and experience.
3. Pre-blowing
The role of pre-blowing in the blowing process is to make the preform take shape, and at the same time, the longitudinal strength of the preform is increased by the longitudinal stretching of the stretching rod. 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 with the cooperation of the one-way valve. The pre-blowing position, pressure and flow can affect the quality of the bottle.
Position: if the pre-blowing position is early, the center point at the bottom of the bottle will be skewed and thinner, the wall thickness of the foot will be uneven and white, the top will be heavy and the bottom will be light, the neck will be hard, and the bottom will be penetrated; If the pre-blowing position is wrong, defects such as light up and heavy down, thickening of the center point and depression will appear.
Air flow Pre-blowing air flow is controlled by one-way valve, and it is appropriate to open 3-4 circles normally. Large air flow, heavy bottom, thin and eccentric center point, white feet, uneven wall thickness; The air flow is small, the center point is thickened, and the weight of segmented parts exceeds the standard.
Pressure: the pre-blowing pressure should be 0.8-1MPa. When the pressure is high, it may cause the upper part to be heavy and the lower part to be light, the center point to be skewed, the foot wall thickness to be uneven, and whitening; When the pressure is low, it cannot be fully stretched, the bottom is heavy, and the center point is thick.
The molding condition of the foot and center of the bottle has the greatest impact on the quality of the bottle. Improper adjustment often causes fatal defects such as bottle explosion (under normal experimental conditions) and leakage.
4. Stretch rod
The stretching rod is installed to stretch the heated preform under the cooperation of pre-blowing and pre-blowing, and it is reset after high-pressure blowing and before exhaust. The stretching rod must be able to move vertically and steadily up and down 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, that is, the bottle blank thickness is 1/3-1/2. If the gap is too large, the center point of the bottle bottom will shift; The gap is too small, and the center point becomes thinner.
5. High pressure blowing
The role of high-pressure blowing is to make the molten material fully extend, close to the mold wall, make the bottle fully formed, and stop the transverse stretching at the same time to improve its transverse 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 gas. The time between them is the pressure holding time in the molding process. The length of this time has a great impact on the stability of the bottle capacity. Lack of high-pressure gas is easy to cause improper bottle forming and lack of foot blowing.
6. Mold
Mold is one of the important factors that affect the bottle blowing process of the automatic bottle blowing machine. The bottle body is a Huff mold, and the bottle bottom is independent, which is a typical blow molding mold. In the process of consumption, the mold should be kept constant temperature, clean and unblocked.
When the heating and cooling system of the mold is defective, the bottle will be skewed, the bottle will tilt, the volume and height will change, and the bottom will become heavier; Maintaining a constant temperature of the mold can also avoid condensation on the surface of the mold.
The shrinkage of PET after molding is relatively large, generally 1.8%, and slightly decreased after glass fiber reinforcement, but still up to 0.2% - 1.0%. Under normal conditions, the shrinkage at high mold temperature is large, and the shrinkage at low mold temperature is small. In order to maintain the stability of PET bottle volume, the mold temperature must be strictly controlled. Generally, the bottle body temperature is slightly higher, 20-45 ℃, and the bottom temperature is lower, 6-15 ℃. High bottom temperature will make the bottom heavier and the center thicker.
There are also nozzles that will affect the forming of PET bottles in practical consumption.