what is the difference between extrusion blow mold and stretch blow mold?

Stretch blowing process and injection blowing process

Extrusion blow molding is the largest type of blow molding method, but also came out earlier a type of blow molding method, suitable for PE, PP, PVC, PETG, thermoplastic engineering plastics, thermoplastic elastomers and other polymers and a variety of blends blow molding, mainly used to produce packaging containers, storage tanks and other industrial parts. Extrusion blow molding is first extruded by the extruder tubular embryo, the material in the extruder after melting and plasticizing extrusion from the head; Then, the clamping and sealing mold of the type embryo. When the type embryo reaches the predetermined length, a section of tube embryo is cut off and placed in the blow mold while it is hot. The mold is closed and clamped at the same time. After blowing the type embryo, the compressed air is blown into the type embryo through the blowing nozzle, and the type embryo is blown into the exact shape of the cavity; Finally, the mold is opened and the product is taken out.

Injection blow molding is a combination of injection molding and blow molding. The mold with bottom is first produced by injection molding, and then transferred to the blow mold for blowing molding. Injection blow molding is the first production embryo. The injection agent will inject the melt into the injection mold with the blowing core tube to form the embryo with the bottom, and then transfer to the blow mold at the blow molding station through the mechanical device for blowing expansion; After blowing the mold, the blowing mold is closed, the compressed air is introduced into the mold through the mandrel hole, and the mold is closely fitted with the blow molding cavity under the action of air pressure. After cooling, it is transferred to the demoulding station. Finally, the product is demoulded. At the demoulding station, the product will be pushed out from the mandrel and fall off or sent directly to the packaging position, and then enter the next cycle of production.