What does it mean to blow bottles in plastic? The equivalent of blowing a balloon, but in the balloon when the balloon added a mold. Of course, this intuitive explanation is too far fetched.

PET bottles can be divided into two categories, one is the pressure bottle, such as filling carbonated beverage bottle; the other is no pressure bottle, such as filling water, tea, oil bottle. Tea beverage bottle is the mixing of the polynaphthalene acid ester two B two (PEN) modified PET bottles or PET with thermoplastic poly aryl ester compound bottle, bottle is hot in the classification, can heat more than 80 DEG C; water bottle is a bottle of cold, no requirement for heat resistance. In the forming process, the hot bottle is similar to the cold bottle. The paper mainly discusses the forming process of the pressure beverage bottle in the cold bottle.

1 equipment

With the continuous progress of science and technology and the scale of production, PET bottle blowing machine automation is becoming more and more high, the production efficiency is also getting higher and higher. Equipment production capacity continues to increase, from the previous production of thousands of bottles per hour to the current production of tens of thousands of bottles per hour. The operation of the past by the manual button type development for the present full computer control, greatly reducing the difficulty of the process, increased the stability of the process.

At present, the injection stretch blow moulding equipment manufacturers are mainly French SIDEL company, KRONES company of Germany, Taizhou, Huangyan Chinese Lange Machinery Mould Co., ltd.. Although different manufacturers, but its equipment are generally similar in principle, including blank supply system, heating system, blowing system, control system and auxiliary equipment of five parts.

2 blow molding process

PET bottle blow molding process.

The important factors that affect the PET bottle blow molding process are bottle blank, heating, pre blowing, mould and environment.

2.1 bottle blanks

Preparation of bottles, first PET slice injection molding for the preform, it requires two times the proportion of recycled material is not too high (below 5%), recovery of not more than two times, and the molecular weight and viscosity can not be too low (molecular weight of 31000-50000, viscosity of 0.78-0.85cm3 / g). Injection molded bottles need to be stored at the top of the 48h to be used. After heating, not run out of the bottle blank, must be stored at the top of the 48h can be used to re heating. Preform storage time can not be more than six months.

The advantages and disadvantages of the preform are largely determined by the merits of the PET material, which should be selected to be easy to blow up and easy to form the material, and to make reasonable bottle blank forming process. Experiments show that the same viscosity of the PET material molding preform, imported raw materials than domestic materials easily blow molding; and the same batch of bottles, production date is different, blow molding process may also have a greater difference. The preform determines the blow molding process difficult, preform requirement is pure and transparent, no impurities, no color, length and halo around the injection point right.

2.2 heating

The heating oven is heated by the heating oven, and the temperature is set by the manual. A far infrared radiation heating bottle blank by far infrared lamp baking oven, oven bottom by the wind turbine thermal cycle, the even temperature in the oven. The bottle body rotates at the same time during the forward movement of the baking oven, so that the wall of the bottle body is heated evenly.

Tube layout in the oven in the general form of "zone", two more, the middle less. The oven heat from the tube opening number, the overall temperature setting, oven power and different heating than common control. The opening of the lamp tube must be adjusted with the pre blowing bottle.

To make the oven to play a better role, the height and the adjustment of the cooling plate is very important, if improper adjustment, inflation prone to blow when the bottle (bottle bigger), stiff neck (cervical material pull open defects).

2.3 pre blow

Preblowing is a very important step two step blowing method, it also refers to the decline in the stretching rod of the blow molding process began preblow, begun to take shape of the bottle blanks. Preblowing position, pre blow pressure and air flow are three important factors in the process of this process.

The advantages and disadvantages of the shape of the pre blow bottle decide the difficulty of the blow molding process and the performance of the bottle. The normal pre bottle shape for the spindle, abnormal, dumbbell, handle shape, as shown in figure 2. The cause of abnormal shape of the local heating of improper pre blow pressure or gas flow shortage, but the size of pre blowing depends on pre blow pressure and preblowing position. In order to maintain the size and shape of all pre blown bottles of the whole equipment in production, if there are differences, it is to look for the specific reasons.

The size of pre blow pressure varies with the bottle size and equipment capacity, the general capacity is big, the pre blow pressure is small, the equipment production capacity is high, and the pre blow pressure is also high.

Even if the same equipment used to produce the same specifications of the bottle, due to the differences in the performance of PET materials, the required pre blow pressure is not the same. Glass fiber reinforced PET material, the smaller the pre blow pressure can make the big molecule bottle at the bottom of the correct orientation; some other improper or inappropriate material forming process of preform, there are a lot of stress concentration is not easy to fade, if the blow injection point nearby, often at the injection point blow or stress testing from the point of injection, burst leakage. According to the orientation condition, the lamp can be removed from the 2-3 branch to the top of the injection point to be opened at the top of the injection point, and the full heating at the point of the injection point is provided.

The bottle blank heating bottle blank two use or exceed the standard storage time, temperature effect due to the two arithmetic, forming process is similar, compared with the normal preform, less than the requirements of heat, it may be appropriate to reduce pre blow pressure.

2.4 auxiliary equipment and mould

Auxiliary equipment mainly refers to maintain the mold temperature. Mold temperature