What is the difference between injection blow molding and extrusion blow molding?

Extrusion blow molding (EBM) is a process in which plastic, or parison, is melted and expelled or extruded to develop a shape in a hollow tube. It thus forms a mold.

The parison is kept and sealed within a metal parent mold. Air is then transferred into the mold facilitating its formation into the intended shape. After the plastic has cooled down, the mold is released and the part is removed.

Extrusion blow molding has two variations: Intermittent and continuous (having a continuous extrusion of the parison).

Injection molding may appear to have similar characteristics to EBM, but it involves a different process. As with EBM, it is a method of manufacturing components and products through the injection of the parison into a mold. Pellets made from plastic are melted and forced (injected) into the mold. Subsequently it cools and becomes a solid, having formed into the shape of the mold. The finished product reflects the exact shape of the mold.

The major difference between injection molding and blow molding is that injection molding is often used for manufacturing solid components, such as tools, kitchen products, and other solid parts. EBM, on the other hand is used to make hollow parts, such liquid soap containers and water bottles.