In this technique, crushed plastics melt in an extruder, pass through a filter and leave it through fine orifices. Then, they are cut with a high-speed blade in molten state, and simultaneously, are sucked by a sucker and pass through cold tubes and dry. Next, they enter a big tank and experience pressure drop. Under the influence of this pressure drop, heavy granules fall to the bottom of the tank and air discharges from the top of the tank.

Water-cooled strand granulation is a method in which plastic parts melt in an extruder, pass through metallic filters, and get the form of molten plastic strands. Then, they pass through a water pool and directed to a small grinding machine where they are crushed and dry. This is a simple technique but the produced granules are not similar to the granules of new raw materials and have sharp corners and plastic content. Moreover, the production line, itself, is not stable, the strands are cut, and the production line needs full-time operators.

Recycled plastic materials with sheet form or sharp corners could not be easily used in the input funnel of these machines. In addition, after mixing process they yield heterogeneous shape due to the non-uniformity of their size compared to other materials. Therefore, the consumers of these materials prefer to purchase materials to form of small plastic granules like new materials. This is done by a line called the Granular Production Line.