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Research progress of plastic extrusion blow molding process

Update:20 Dec 2019
Summary:

Extrusion blow molding is one of the main molding metho […]

Extrusion blow molding is one of the main molding methods for the production of plastic hollow parts. It is suitable for polymers and various blends such as PE, PP, PVC, thermoplastic engineering plastics, and thermoplastic elastomers. It is mainly used for molding packaging containers. Flower pots, storage tanks and vats can also be shaped for industrial parts such as the automotive industry. Extrusion blow molding is the same as other plastic hollow molding. Its main advantages are low product cost, simple process and high efficiency, but its outstanding disadvantage is that the wall thickness and uniformity of the product are not easy to control.

Extrusion blow molding is the process of extruding a semi-molten plastic pipe blank (parison) into a mold of various shapes while hot, and then blowing compressed air into the pipe blank to inflate it, so that It is tightly formed on the cavity wall, and the hot forming process of the hollow part is obtained after cooling and demolding. Its entire forming process can be divided into three stages: parison formation, parison inflation, and cooling and solidification.

Researchers at home and abroad have tried to use different methods to study the various stages and the entire process of extrusion blow molding from the 1960s to the present, but in general can be divided into two categories: experimental research and numerical analysis technology . The numerical analysis method is based on the three basic equations of the continuity equation, the motion equation, and the energy equation. A large number of assumptions must be made to simplify the equation, and the finite difference or finite element method is used to solve it. Moreover, some rheological parameter data in the constitutive equation are not easy to obtain. For complex shapes of work-in-progress, it takes a lot of computer time. Experimental research is the simplest and most direct method.