Used plastic pelletizing systems are a type of equipment that is used for creating pellets out of plastic. It is among the most vital intermediate processes in plastics. There are four primary steps to the complete process, which include: strand pelletizing, underwater, hot ring, and hot cut.
There hasn’t been much change to the technology that is used for these processes over recent years, which means that used plastic pelletizing systems can provide a considerable return on investment. When purchased new, the typical lifespan of equipment from a good manufacturer is greater than 20 years, provided that it has been properly maintained.
Plastic pelletizing systems function by adding raw materials – which usually consist of powders – to an extruder’s barrel. Within that barrel, pressure and heat are used to melt the powders, as they are mixed together by a rotating screw. The result is a consistent and uniform molten product. This substance is then sent through a screen, which generates pressure within the extruder barrel, as it filters out any impurities and controls the flow of the molten product on its way to the die. The die settings will determine the shape and diameter of the molten plastic.
After that point, the four steps of the completed process can occur. The first option is strand pelletizing, Once the molten plastic has been through the extruder, a strand die will form a series of strands (like spaghetti) that are then immersed in water to cool them down. When they’ve cooled, they are then dried of the excess water using an air stripper. The cooled strands are then cut by the strand pelletizer. In this case, the number of holes is proportional to the extruder size.
The heat source is the next consideration when purchasing this equipment. This can be either oil or electric. Those based on electric are easier to achieve constant temperature maintenance and they are cleaner to operate. . At the same time, there are some applications that require oil. Among the manufacturers of plastic pelletizing systems, Extrusion Dies Industries (EDI) is the most common.
When considering the water bath purchase, issues to think about include the depth, length, and width of the submersion chamber, as it needs to be big enough for holding the strands. The water bath size is typically matched to the extruder throughput. It is recommended that preference be given to those made with stainless steel, as they won’t rust, however other materials include aluminum and carbon steel.
When buying the air stripper, make certain that the lip width is great enough to allow the strands to be drawn through and ensure that it has strong enough horsepower.
When a used strand pelletizing system is being considered, make sure that the strand guide and entrance width are appropriate to the number and size of the strands. Look at the rotor type (solid helical or removable blades), and the number of blades in either case. Ensure that the horsepower of the unit is enough to spin the rotor and cut the pellets. Common manufacturers include Cumberland and Conair.
The screens may be rectangular or round, but should match the size of the extruder. Those with more decks produce greater filtration levels. Round screen manufacturers include Kason, Sweeco, and Midwestern, while Rotex and Witte make rectangular screens.
Underwater pelletizing is another processing option, in which an adapter is connected to the extruder either with or without a screen changer, and links it to a system made up of a die, a cutting system, a water system, and a spin dryer. This process involves cutting molten material into pellets after it has moved through the die and into a water slurry. The actual pelletizing process occurs underwater, after which the pellets are sent to a spin dryer and screen-sorted.
These pelletizers must be sized so that the gallons per minute of water flow will match the need for the extruder’s material production rate. Among the most common manufacturers are Farrel and Gala.
The third form of pelletizing is the water ring process. This works in the same way as the underwater process, except that the cut is made while the plastic is still hot, and then the pellets are cooled within a ring of water. As the plastic makes its way through the die, the pelletizer uses water to throw the pellets against the ring wall, where they instantly cool and are then dried in a spin dryer and size-sorted through a screen.
When shopping for a ring pelletizing system, look into the capacity, manufacturer, and model. Common manufacturers are Xaloy, Beringer, and PTI.
The fourth and last processing option is hot cut pelletizing, in which the pellets are cut while they are still hot, and then cooled using a blower before they are size-sorted with a screen. This is the most common process used for making PVC pellets. The manufacturer best known for this equipment is Cincinnati Milacron.
When preparing to purchase used plastic pelletizing systems, keep the manufacturer, age, horsepower, rotor type, and screen holes in mind. Perry Videx has a large inventory of used equipment of this nature. Contact the company today to discuss your unique needs.