Extrusion blow molding

Plastic pellets [1] are supplied via a hopper into a rotating screw [2] whose spiral shape moves the pellet forward through a heated chamber [3].The pellets are heated gradually and turns into a homogeneous plastic melt as it approaches the end of the helical screw.

The molten mass is extruded through a die [4] into a tubular profile, in which a cavity is created by the center core comprising a tube.

A: The profile then passes between two separated mold halves.

B: When the profile reaches the mold halves the bottom of the molds are closed which pinch the lower end of the profile and the mold clamps the center of the die core. Then the extruded profile is pressurized from the inside through the center core allowing it to expand and finally conform to the mold walls.

After the mass solidifies the mold halves are separated and the part is removed and the process is repeated.