Blow Molding Process Types: EBM, IBM, and SBM

The three common blow molding processes are extrusion blow molding, injection blow molding (IBM), and stretch blow molding (SBM). Each process forms hollow plastic products, but the way it creates and blows the preform or parison is different, so the right choice depends on product shape, material, precision, and production volume.

Extrusion blow molding makes hollow plastic products by extruding a hot tube called a parison, closing the mold around it, and blowing compressed air into the parison. It is used for bottles, containers, industrial parts, products with handles, complex hollow shapes, and multi-layer structures. Common materials include PE, PP, PVC, PETG, EVOH, TPE, TPV, Nylon, and related grades.

Injection blow molding combines injection molding and blow molding. The process first injection molds a small preform, then transfers it to a blow station where it is heated and blown into the final container shape. IBM is commonly used for small, precise containers such as pharmaceutical bottles, cosmetic packaging, and single-serve containers. It offers good surface finish and tight dimensional control.

Stretch blow molding is mainly used for PET bottles and containers. A preform is first injection molded, then reheated, stretched axially and radially, and blown into the mold. SBM is known for lightweight, strong, clear bottles with uniform wall thickness, especially beverage bottles and carbonated drink containers that require pressure resistance.

Extrusion blow molding is often chosen for design flexibility, lower tooling cost, broader material options, and the ability to make handles, larger containers, complex hollow parts, and multi-layer structures. IBM and SBM have advantages for small precise bottles or PET beverage bottles, but EBM is usually more practical for varied shapes, larger products, and industrial hollow parts.