There are three parts in the blow molding process: stre […]
There are three parts in the blow molding process: stretching-first blowing-second blowing. Because these three processes are very short in time, they must be coordinated in place, especially the first two steps have determined the overall distribution of the material, the blow molding machine This is where the quality is. Therefore, the following factors should be adjusted: the timing of the start of stretching, the stretching speed, the timing of the start and completion of the pre-blowing, the pressure and flow of the pre-blowing, etc. It is best to control the temperature of the entire preform and the temperature of the inner and outer walls of the preform. gradient.
The blow molding process 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 tensile, tensile, and impact strength are improved. Very good air tightness. The wall thickness of the preform should not exceed that of the hollow blow molding machine. It is carried out between the glass transition temperature and the crystallization temperature, and is generally controlled between 90-120 degrees. In this interval, PET behaves as a high-elasticity, rapid blow molding, and a transparent mold after cooling and setting. In the one-step method, this temperature is determined by the length of the cooling time in the injection molding process for the hollow blow molding machine, so it is necessary to connect the injection-blowing station.
There is a magnifying glass at the bottom of the bottle: too much material at the bottom of the bottle, too late pre-blowing, and too low pre-blowing pressure. There are wrinkles in the bottom of the bottle: the temperature at the bottom is too high, the cooling at the gate is not good, the pre-blowing is too late, the pre-blowing pressure is too low, and the flow is too small. The whole bottle is turbid: opaque and can't be cooled. Partially whitish: Excessive stretching, the temperature here is too low, or the pre-blowing is too early, or the stretch rod is hit.
The upper thickness of the blow molding machine and the lower thickness: delay the pre-blowing moment or lower the pre-blowing pressure to reduce the air flow. Thick bottom and thin top: the opposite of the above. There are wrinkles under the bottleneck: the pre-blowing is too late or the pre-blowing pressure is too low, or the billet here is not well cooled. White bottom: the preform is too cold, stretched over fire, pre-blowing too early or pre-blowing pressure is too high.