The blow molding process is used to produce hollow bodies such as canisters and barrels, as well as household items such as watering cans or PET bottles.

Blow molding combines two plastic processing methods. First, a hot plastic tube must be formed using extrusion.

1. For this purpose, the granular starting material is liquefied as in classic plastic extrusion and pressed out vertically downwards through an extrusion tool (also known as a die). Care must be taken to ensure that the tube has a certain degree of dimensional stability, but at the same time is not too cold to be moulded. The tube now descends from above between the two open parts of the blow moulding tool, which only forms the outer contour of the blow moulded part. The wall thickness of the blow moulded part is determined by the thickness of the tube and the ridge of the stretching during inflation.
2. The hose must be long enough so that it can be squeezed together at the top and bottom when the mould is subsequently closed.
3. A needle is inserted into the heated hose from above, through which air is blown into the hose. The resulting overpressure inflates the hose like a balloon until the hose, which is still hot, completely touches the wall of the cooled mould.
4. There, the plastic material cools and solidifies until it is sufficiently dimensionally stable.
5. After opening the mould, the blow-moulded part can be demoulded.

After demoulding the hollow body, a processing step follows in which the remains of the tube are removed. In the case of hollow bodies with handles, the excess squeezed material in the handle area is ideally also punched out. Depending on the customer's requirements and the degree of automation of the process, further manual steps can follow, such as reworking the crimped seam with a deburring knife.

Due to its larger dimensions, the blow-moulded part generally takes up considerably more space for storage and shipping.due to its larger dimensions, the blow-moulded part generally takes up considerably more space for storage and shipping.