1. The polymer is transported, melted, kneaded, and pumped out to form a parison in the extruder. At this stage, the factors affecting the wall thickness distribution are: 1. The molecular weight distribution of the material and the average molecular weight; 2. The temperature control system and screw speed of the blow molding machine, among which the temperature control system includes the temperature of the hopper, the temperature of the zone 1, 2, 3, and 4 of the barrel, the temperature of the flange, and the zone 1 and 2 of the storage die. , Zone 3, zone 4 temperature.
2. The stage where the parison is extruded from the gap between the die lip and the die core is called the blanking stage. At this time, common phenomena are the swelling of the embryo and the vertical extension of the embryo. The factors affecting these two phenomena are: the die diameter and wall thickness control system of the blow molding machine, where the control system includes the axial wall thickness control system and the circumferential wall thickness control system, which are used to adjust the gap between the die lip and the core of.
3. Pre-blowing stage of preform In order to avoid contact and adhesion of the inner surface of the preform, and to improve the uniformity of the wall thickness of the product, pre-blowing of the preform is required. During the pre-blowing stage of the embryo, air is sprayed from below the embryo to the embryo to protect the embryo and reduce its vertical extension. At this stage, the factors affecting wall thickness distribution are: pre-blowing pressure and pre-blowing time.
4. In the stage of high-pressure blow of the parison, the parison is inflated under high pressure to make it close to the mold cavity to achieve plastic molding of the product. At this stage, the common phenomenon is that the embryo is deformed by high pressure inflation, and the embryo is deformed by contact with the cavity. The factors that affect this kind of situation are: the shrinkage of the material; the pressure and time of blowing; the material and structure of the mold; the mold exhaust system and the mold cooling system, such as the distribution of the cooling water channel, the cooling water inlet temperature, etc.