PET bottle blowing process is divided into four stages: stretching, pre blowing, bottle blowing and cooling. After the temperature adjustment process is completed, the machine transfers the bottle blank from the conveying chain of the heating furnace to the bottle blowing mold. When the mold is closed, the stretching rod moves downward to stretch the bottle blank along the axis. The lowering speed of the stretching rod is controlled by the stretching cam. The material distribution along the axis of PET bottle is formed at this moment. The stretching speed is one of the key parameters affecting the axial distribution of material. If it is very fast, the material on the top of the bottle is easy to be too much, resulting in insufficient material distribution on the upper part of the bottle body and reduced overall mechanical properties. Perhaps if it is very slow, the material on the top of the bottle is easy to be too small, which may also lead to the decline of the overall mechanical performance, and the ideal bottle will not be blown out.
Oral liquid pharmaceutical PET bottle t001-60ml
The function of pre blowing is to ensure that a certain distance is maintained between the pet preform material and the stretching rod during the stretching process, so as to avoid the contact between the preform wall and the stretching rod. During the stretching process, if the bottle blank is higher than the contact between the material and the stretching rod, the material will be cold in the stretching rod. In addition, the friction of the stretching rod and the adhesion of the hot PET material will directly lead to the failure of the contacted part to be stretched as expected and the failure of blowing qualified bottles. Therefore, the pre blowing process is very important.
The pressure and time setting in the pre blowing process of PET bottle blowing is also very important. The pre blowing pressure is generally adjusted about 6-10bar. If the pre blowing is not enough, the purpose of separating the stretching rod from the bottle wall material will never be achieved. If the pre blowing is too much, the bottle wall material will contact the inner wall of the mold in advance without being fully stretched, which will also affect the distribution of the material in the direction of the highest point, The expected material distribution is never achieved.