What is the difference between blow molding process and injection molding process
Blow molding products are hollow; Injection molding because there is an injection port, there will be a small part of the molded product that is not needed. There will be a process to cut it off, but it can be found if you observe it carefully.
Injection molding: a method in which thermoplastic or thermosetting molding materials are uniformly plasticized in the heating barrel, and then pushed into the mold cavity of the closed mold by the plunger or moving screw.
Injection molding is applicable to almost all thermoplastics. In recent years, injection molding has also been successfully used to form some thermosetting plastics. The molding cycle of injection molding is short, and the molding volume can range from a few grams to tens of kilograms. It can form molded products with complex shape, accurate size and metal or non-metal inserts at one time. Therefore, this method has strong adaptability and is suitable for production.
Blow molding: it is a method to blow the hot parison closed in the mold into hollow products by gas pressure, or blow the tube parison into tube membrane without mold. The method is mainly used for manufacturing various packaging containers and tubular films.
Those with melt index of 0.04 ~ 1.12 are excellent hollow blow molding materials, such as polyethylene, polyvinyl chloride, polypropylene, polystyrene, thermoplastic polyester, polycarbonate, polyamide, cellulose acetate and polyacetal resin, among which polyethylene is widely used.
Injection blow molding: the plastic is first made into a bottomed parison by injection molding, and then the parison is moved to the blow mold to blow into a hollow product.
Extrusion blow molding: the plastic is first made into a bottomed parison by extrusion method, and then the parison is moved to the blow mold to blow into a hollow product.
Stretch blow molding: stretch blow molding is a kind of blow molding of biaxial directional stretching. Its method is to stretch the mold longitudinally, and then blow it with compressed air to achieve transverse stretching. Stretch blow molding can greatly improve the transparency, impact strength, surface hardness and rigidity of products. It is suitable for blow molding of polypropylene and polyethylene terephthalate.
Blown film method: a method of forming thermoplastic film. The plastic is extruded into a tube by extrusion method, and then it is continuously expanded to a certain size of tubular film with the help of air blown into the tube. After cooling, it is folded and wound into a double-layer flat film.
