In the extrusion blow moulding process, thermoplastic resins and colour masterbatch granules are mixed at the intake of a single screw extruder. The thermoplastic resins generally come out of silos while the colour masterbatch granules come out of containers on the machine pedestal. Flash from blow moulding production is ground directly at the machine and the regrind is directed from the grinder over a cyclone and blown into a buffer container. All three components (thermoplast, colour masterbatch and and regrind) are dosed respectively through a dosing axle of the GRAVICOLOR (gain-in-weight). Scrap is generally reground centrally, in some cases it is regranulated afterwards. This material is fed back into the buffer container through a hopper loader and then reintroduced into the process.

Due to the high throughputs in the blow moulding process it makes sense to have a central vacuum system when several machines are involved. In a vaccum line system, the air volume of the conveying blower as well as the vacuum tubing are calculated so that only one hopper loader can convey at a time. This means that the proportion of blowers to the number of conveying units in the line must be chosen so that every point of consumption is supplied with sufficient material at all times. In a central vacuum system several hopper loaders are capable of feeding simultaneously per line or within the entire system. Through the variable allocation, output must not be reserved which results in considerable energy savings. The parallel-operated pumps will shut off automatically (pressure controlled) depending on air requirements. Since full vacuum is present at all time and does not have to be built up after a run-on time as in lines, higher throughput rates can be attained.

In the extrusion blow moulding process, a hose is generated by means of a mould at the end of the extruder. The hose is cut to length and fed to the final blow moulded product for further processing.