A plastic pelletizing system is equipment that creates plastic pellets and is one of the most important intermediate processes in plastics. There are four main processes: strand pelletizing, underwater, hot ring, and hot cut. The technology has not changed significantly in recent years and used plastic pelletizing equipment offers a high return on investment. The typical life of a new plastic pelletizing system from a reputable manufacturer will exceed 20 years if properly cared for and maintained. The most important considerations when buying a new or used plastic pelletizing system are cost, quality and delivery time.
How Plastic Pelletizing Systems Work
Plastic pelletizing systems add raw materials, often powders, to the barrel of an extruder. Inside the barrel, heat and pressure are applied to melt the powders and a rotating screw mixes it together. This creates a uniform and consistent molten product. The molten product is passed through a screen that creates pressure in the extruder barrel, filters impurities, and controls flow to the die. The diameter and shape of the molten plastic is determined by settings on the die. From this point, four different processes can be applied.
Different Plastic Pelletizing Processes Strand Pelletizing
One option to process compound plastic is strand pelletizing. After the extruder process, a strand die creates a series of spaghetti-like strands that are cooled in water. Once cooled, an air stripper removes excess water. The strand pelletizer then cuts the cooled strands. In the case of the strand die, the number of holes is proportional to the size of the extruder. Another consideration is heat source: electric or oil. Electric systems are cleaner and easier to maintain at a constant temperature, however some applications require oil. The most common manufacturer is Extrusion Dies Industries (EDI). It can be difficult to determine the brand of the die without documentation.
Issues to consider when purchasing a used water bath include the length, width, and depth of the submersion chamber. It’s important to ensure the water bath is big enough to hold the strands. The size of the water bath is generally matched to the throughput of the extruder. Construction material is also important with stainless steel the best choice because it doesn’t rust. Other materials include carbon steel and aluminum.