There are three basic types of die face hot cutting system, airflow granulator, water spray (water ring) granulator and underwater granulator. A typical system includes a die, a cutting chamber, an electric rotary blade, a cooling medium, and a method for drying pellets (if water cooling is used).
The die is an important part of the die surface thermal granulation system. It is installed vertically or horizontally, and is usually heated by oil, steam, or drum or band electric heaters. Electric heating is usually used for smaller dies; but larger dies are usually heated by steam or oil. Die structure materials have different materials, but no matter what material or heating medium is used, the diameter of the die orifice must be uniform; there must be enough heat to maintain the temperature of the polymer during the entire extrusion process; the pair of pelletizing knives The rotating die surface must be tough and smooth-these are necessary to make uniform pellets.
When the molten polymer is extruded from the die, a pelletizing knife rotating at a high speed cuts it into pellets. The pelletizing knife is in contact with or very close to the mold surface. After the pellets are cut, they are thrown away from the knife by centrifugal force and transported to the cooling medium.
The size, shape, material and installation method of the pelletizing knife can be different. In some systems, the pellet cutter has a spring applied load to automatically adjust the distance between the pellet cutter and the die; while in some systems, the distance between the pellet cutter and the die must be manually adjusted. Since the life of the cutting knife depends on the precision of the knife-die centering, the abrasiveness of the polymer and the aggressiveness of the operator, it is advisable to cut the polymer pellets in the molten state.