Nine major problems most likely to occur in the quality of blow-molded plastic bottles and their solutions

Author: MULAN -Plastic Molding Manufacturer

The quality of blow-molded PET plastic packaging drinking water bottles is prone to nine major problems and solutions: Problem 1: If the top is thick and the bottom is thin, it is necessary to delay the pre-blowing time, or reduce the pre-blowing pressure and air flow. Problem 2: The bottom is thick and the top is thin, which is the opposite of the problem that has been solved. Problem 3: There will be wrinkles under the bottleneck, the pre-blowing is too late or the pre-blowing pressure is too low, or the billet cooling here is not good. Problem 4: The bottom is white, the main reason is that the preform is too cold; at the same time, it is stretched too much; the pre-blowing time is too early or the pre-blowing pressure is too high. Question 5: There is a magnifying glass phenomenon at the bottom of the bottle, and there is too much material at the bottom of the bottle; the pre-blowing is too late, and the pre-blowing pressure is too low. Problem 6: There are wrinkles in the bottom of the bottle, the bottom temperature 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 rate is too small. Question 7: The whole bottle looks turbid and less transparent, and the cooling is not enough. Problem 8: Partial whitening: excessive stretching, the temperature here is too low, or the pre-blowing is too early, or the stretching rod is touched. Question 9: The eccentricity of the PET plastic bottle bottom may be related to the preform temperature, stretching, pre-blowing, high-pressure blowing, etc. The solution is to first reduce the temperature of the preform; at the same time, speed up the stretching speed; check the gap between the tie rod head and the bottom mold; delay the pre-blowing, reduce the pre-blowing pressure; delay the high-pressure blowing; check after processing Whether the preform will be eccentric. Hollow blow molding product molding method: (1) parison forming The parison molding method of hollow products can be divided into two types, namely, extrusion molding in extrusion blow molding and injection molding in injection blow molding. Extrusion molding parison is to plasticize and melt the raw materials in the extruder, and then extrude the molten material to form a parison. Injection molding parison is to melt and plasticize the raw material in the plasticizing injection system of the injection molding machine, and then inject it into a blank shape. (2) Blow molding of parison The blow molding of the parison can be divided into stretch blow molding, hot billet blow molding and cold billet blow molding. ①Stretch blow molding Refers to the parison that is extruded or injection molded, mechanically stretched through the internal stretching mandrel or external stretching fixture, and then the middle diameter is inflated with compressed air to obtain transverse stretching and become biaxial stretching hollow products. The products formed by this method, if completed on the extruder, become extruded——to stretch——Blow molding (referred to as extrusion blowing); if it is completed on an injection molding machine, it becomes an injection molding——to stretch——Blow molding (referred to as injection molding stretch blow). ② Hot billet blow molding It means that the stretching and blowing work is performed on this equipment immediately after the parison has not cooled down. It can also be called one-step production. ③Cold blank blow molding It means that the parison is cooled after it is formed. Preheating, stretching and inflation of the parison is done on another piece of equipment. It can also be called two-step production. Compared with cold billet blow molding products, hot billet blow molding has the following characteristics. The production cycle of hot blank blown products is short, and the blown molded products are stretched before the parison is cooled, which saves the heating time of the parison and saves energy. Cold billet blow molding products have no requirement on the processing equipment of the parison. The parison can be processed and produced on the extruder or the injection molding machine. To complete, which is conducive to specialized production. However, this cold blank blow molding product should be heated before blowing, which not only increases the production and molding time of blow molding products, but also wastes energy. Difficult to detect in time.