Blow molding, or hollow (blow) molding, is a plastic forming process that involves inflating a heated thermoplastic parison within a mold to form a hollow product. There are three primary types of blow molding, each with its unique characteristics and applications.
1.extrusion blow molding. This method is primarily used for unsupported parisons. In this process, a tube of heated plastic is extruded through a die and then clamped between the two halves of a mold. Air pressure is then introduced into the tube, causing it to expand and take the shape of the mold cavity. Extrusion blow molding is characterized by its high production efficiency and relatively low equipment costs. However, it may have limitations in terms of product thickness control and material distribution.
2.injection blow molding, primarily used for parisons supported by a metal core. In this process, a plastic mass is injected into a mold cavity to form a parison, which is then inflated to form the final product. Injection blow molding offers better control over product wall thickness and material distribution, resulting in higher product quality. However, the equipment costs are higher, and it may be less suitable for large-scale production.
3.stretch blow molding, which combines extrusion or injection molding with stretching to produce biaxially oriented products. This method significantly reduces production costs and improves product performance. Stretch blow molding is commonly used to produce bottles and other containers that require high strength and clarity.
