The feed extruder sends the crushed and mixed materials to the conditioner to give them a certain amount of moisture and temperature. The quenched and tempered mixed materials are sent to the expansion bin. The materials pass through different areas driven by the high-speed rotating screw. The temperature and pressure of the materials gradually increase due to friction, and the pressure control locks between the areas further adjust the pressure.

                     Expansion temperature and pressure reach a certain level at the outlet of the conical spiral of the extruder head. The temperature of the material rises to 135~160 degree and the pressure is 15~40 atmospheres. At this time, although the temperature of the water is higher than 100 degree , the pressure is also far higher. The pressure is higher than one atmosphere, which avoids the occurrence of boiling phenomenon. When the material enters the atmospheric pressure environment through the ring die hole, the pressure suddenly decreases and the steam escapes rapidly, causing the material to expand violently.