The molding parameters of each stage are analyzed from the blow molding process. PP Bottle production blow molding process can be divided into four stages 分为


(1) The parison formation stage The polymer is conveyed in the extruder, melted, kneaded, and pumped out into the parison formation stage.

At this stage, the main process parameters affecting wall thickness distribution are:
① Molecular weight distribution and average molecular weight of materials 
②The temperature control system and screw speed of the blow molding machine, where the temperature control system includes the hopper temperature, the barrel 1 zone, 2 zone, 3 zone, 4 zone temperature, flange temperature, and storage die head zone 1, zone 2, Zone 3, Zone 4 temperature.



(2) The parison blanking stage The parison is extruded from the gap between the die lip and the core as the blanking stage. At this time, the two phenomena of parison expansion and parison vertical expansion affect the parison forming. The main process parameters affecting wall thickness distribution are the die diameter and wall thickness control system of the blow molding machine, where the control system includes an axial wall thickness control system and a circumferential wall thickness control system to adjust the gap between the die lip and the core.



(3) In order to avoid contact and adhesion of the inner surface of the parison, to improve the uniformity of the wall thickness of the parison, the parison must be pre-inflated. During the pre-blowing stage of parison, air is sprayed from under the parison to the parison to protect the parison and reduce its vertical extension. At this stage, the main process parameters that affect wall thickness distribution are pre-blowing pressure and pre-blowing time.



(4) High-pressure blow molding stage of the parison. The high-pressure inflation parison is brought into close contact with the mold cavity to realize the plastic molding stage of the product. At this stage, what affects the product molding is that the parison is deformed by high pressure inflation, and the parison is deformed by contact with the cavity. The main process parameters that affect wall thickness distribution are: material shrinkage, blowing pressure, time, mold material, structure, mold exhaust system, and mold cooling system, such as cooling channel distribution, cooling water inlet temperature, and so on. Although there are many factors that affect the quality of blow molded products, once the production conditions and product requirements are determined, adjusting the blow molding process parameters can effectively improve the product quality. Optimized process parameters can improve production efficiency, reduce raw material consumption, and optimize the overall performance of the product.



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