Structure and Working Principle Analysis of Plastic Pelletizing Machine

The plastic pelletizing machine is an important equipment used to recycle plastic waste into granular plastic raw materials for various applications. This article analyzes its key structural components and working principles.

Structurally, the pelletizing machine consists of a feeding section, melting section, filtering section, pelletizing section and cooling section. The feeding section contains a hopper and screw conveyor to transport the plastic scrap into the barrels. The barrels are heated to melt the plastic using electrical heaters or a hot oil system. To homogenize the melt, the machine has a rotating screw inside the barrel.

The molten plastic then passes through a breaker plate and screen to filter out contaminants. The filtered plastic flows into the pelletizing die which is basically a metal plate with holes that shapes the plastic into strands. The strands are then cooled using air or water systems to solidify the plastic. Pellet cutters like rotary knives cut the strands into small and uniform plastic pellets.

The working principle involves simultaneous melting, mixing and pressurizing of plastic inside the barrel by the rotating screw. This builds pressure and pushes the melt into the die. The die shapes the plastic into spaghetti-like strands which are cooled and cut into pellets.

The pellet shape and size is determined by the die hole design. The screw speed, temperature controls and pellet cutter rpm ensures smooth and continuous production of pellets. If air cooled, a centrifugal drier may be used to dry the pellets. The key to quality pellets is properly controlling the plastic viscosity, temperature, pressure and cooling rate.

Understanding the workings of the pelletizing machine is crucial for equipment selection, efficient operation and maintenance. The components must be made of wear-resistant materials for longevity. By analyzing the structure and principles, manufacturers can also optimize designs for energy efficiency, flexibility and pellet quality.