Granulation Most polymers must be blended before they are made into the final product and then pelletized to become a marketable raw material. There are many different granulator designs, but all granulators can be divided into two major categories: cold-cut pelletizing systems and die-surface hot-cut pelletizing systems. The main difference between the two is the timing of the pelleting process. The cold pelletizing system cuts pellets from the solidified polymer at the end of the process; whereas in the hot die pelletizing system, the pellets are pelletized when the molten state polymer emerges from the die, and the pellets are processed downstream. cool down. Both pelletizing systems have their own advantages and disadvantages.
Cold pelletizing system The cold pelletizing system includes a die, a cooling zone (air-cooled or water-cooled), a drying zone (if water-cooled) and a pelletizing chamber. There are two major types of cold pelletizing systems, namely pellet pelletizers and strip pelletizers.
The pellet melter melts the polymer from a mixing apparatus through a belt die or roll mill to a thickness of polymer pellets. The flakes are solidified and cooled by a distance during transportation and then cut into round or square granules with a guillotine knife in one compartment.
Tablet granulation is the oldest method of producing pellets and can be used for various polymers from nylon to polyvinyl chloride.
Heavy weight. It is reported that the accuracy is quite good and the granulation ability can reach 1843.69 kg/h. This is a cold-cut method, and the noise emission is higher than the method of pelletizing from the molten polymer. The life of solidified cutting polymer blades is short, and the generation of powder often becomes a problem. Some "polymer chains" can be seen for some polymers.
The use of strip pelletizers is almost as old as pellet pelletizers. Including die, cooling section (bath or blower), drying section (if water-cooled) and slicing knife. Extruded molten polymer is extruded through a horizontally mounted die using an extruder or gear pump (a modern die is precision machined and uniformly heated to produce a consistent quality bar). After the strip is discharged from the die, it is cooled with a blower or air/vacuum facility or cooled with a water bath. If water cooling is used, the strips must pass through a drying section where they are blown with forced air and the strips are sent to the pelletizing chamber. Using the shear action of a pair of fixed and rotary knives, the strip is precisely cut to the desired length.
The pellets have a diameter of 3.175 mm and a length of 3.175 mm with clear edges and corners.
The traditional method of drawing the strip is to stretch the strip through the cooling section (most commonly a water bath), sometimes causing the strip to fall or inconsistent dimensions. This is most common in polymers with poor strength in the molten state, such as polypropylene, polyester, and nylon. When the strip falls, the material is scrapped, so operators must pay close attention. If the strips are drawn inconsistently, the downstream pellets must be sieved.
Other methods of striping can be monitored without the operator's close attention. The solution is to use a motor-driven slotted feed conveyor to support and divide the strips from the die to the pelletizer. This kind of strip material conveyed by the screw is relatively uniform in size, does not fall down and is therefore less discarded. Some of these methods can have a production capacity of 6803.89 kg/h, compared with about 1814.37 kg/h for the method of stretching into strips, because operators can only watch a limited number of strips.
Strip production line is not costly, easy to operate, and easy to clean. This has advantages for colorant compounding because replacement of two batches of different colorants must thoroughly clean the equipment. However, the defect of the strip forming method is that the cooling section needs to occupy space, and its length is determined according to the temperature requirement of the polymer.
Die surface hot cutting system Die surface hot cutting system has three basic types, namely air flow granulator, water spray (water ring) granulator and underwater granulator. Although this type of system can be designed differently, typical systems include a die, a cutting chamber, an electric rotary blade, a cooling medium, and a method of drying the pellets (if water cooling is used).
The die is an important part of the hot die pelletizing system. It is mounted vertically or horizontally and is usually heated with oil, steam or cartridge or belt heaters. Electric heating is usually used for smaller dies; however, larger dies are usually heated with steam or oil. The die structure materials have different materials, but no matter what kind of material or heating medium is used, the die orifice diameter must be uniform; there must be enough heat to maintain the temperature of the polymer during the entire extrusion process; The rotating mold surface must be tough and smooth - these are necessary to make uniform pellets.
When the molten polymer is extruded through a die, it is cut into pellets using a guillotine knife that rotates at a high rotational speed. The typical situation is a pellet cutter or contact or very close to the die surface. After the pellets are cut off, they are thrown off the knife by centrifugal force and transported to the cooling medium. The size, shape, material, and mounting of the pellet cutter can vary. In some systems, the cutting knife has a spring applied load to automatically adjust the spacing between the cutting knife and the die; some systems must manually adjust the spacing of the cutting knife to the die. Since the life of the cutting knife depends on the accuracy of the alignment of the tool, the abrasiveness of the polymer and the aggressiveness of the operator, it is advisable to cut the polymer pellets in the molten state.
Air flow granulators are recommended for polymers that are sensitive to heat and long residence times, such as polyvinyl chloride, TPR, and crosslinked polyethylene. The pelletizing rate is up to 4989.52 kg/h. The flow path of the polymer from the extruder to the cutting chamber should be kept as short as possible and the minimum amount of heat should be used. When the polymer is extruded through the die, the rotational force of the die surface rotates it into pellets. After the pellets are cut, they are thrown away from the rotary knife and trapped in the air that is forced to circulate in the specially designed cutting chamber. The air stream initially quenches the pellet surface and brings it out of the pelletizing chamber to the cooling zone. Fluid bed dryers are often used to cool pellets. The pellets slide down an adjustable ramp while the circulating fan blows through the pellets. Adjusting the bevel angle can extend or shorten the dwell time of the pellets in the dryer. Another common method of cooling is to discharge the pellets from the cutting chamber into a water bath and remove the water using a fluid bed dryer or a centrifugal dryer.
Water-spray granulators are suitable for most polymers except for polymers with low melt viscosity or stickiness. This type of equipment is also known as a water ring pelletizer. The granulation rate is 13607.77 kg/h.
The molten polymer was extruded from the hot die and cut into pellets by a rotating knife rotating with the die surface. This granule system features a specially designed water jet cutting chamber. The water flows spirally until it flows out of the granule chamber. After the pellets are cut, they are thrown into the water stream for preliminary quenching. Pellet water slurry is further cooled into a pellet slurry tank and then sent to a centrifugal dryer to remove moisture.
The underwater pelletizer is similar to the air pelletizer and the water jet granulator except that it has a steady flow of water through the die surface and is in direct contact with the die surface. The cutting chamber is sized just enough to allow the cutter to rotate freely over the die surface without limiting the flow of water. The molten polymer is extruded from the die, the rotary knife cuts the pellets, and the pellets are brought out of the pelletizing chamber with tempered water and into a centrifugal dryer. In the desiccator, water is drained back to the tank, cooled and recycled; the pellets are removed by a centrifugal dryer.
Underwater pelletizers use a die with uniform heat distribution and special insulation. Small pelletizers use electric heating; large pellet cutters require oil- or steam-heated dies. Process water is normally heated to its maximum temperature, but its heat should not be sufficient to have a detrimental effect on the free flow of the pellets. Underwater pelletizers are used for most polymers, and some models can achieve a pelleting capacity of 22,679.62 kglh. The way water flows through the die face when used for pelleting low viscosity or sticky polymers is a great advantage, but the characteristics of some polymers such as nylon and certain brands of polyester may cause the die to freeze . Other advantages include: because of pelletizing in the molten state, the water plays a role of acoustical barrier and emits less noise; the replacement of the pelletizing knife is less frequently compared to the cold cutting system.
Centrifugal Granulators Centrifugal Granulators Because the die only uses or requires only a minimum amount of heat, rather than a hot die face pelletizer, and because it is a pellet of molten polymer, it is not a cold cut system. Self-contained. The granulator of this type is characterized by the use of a cylindrical die, with the extrusion holes distributed along its circumference. The molten polymer is fed at atmospheric pressure. The extrusion pressure is formed by the depth of the melt on the rotor, the rotor speed, and the relative density of the polymer. As the cylindrical die rotates with its mandrel at a high speed, the centrifugal force acts to evenly flow the molten polymer to the individual orifices on the die. As the polymer exits the extrusion orifice, the rotating die forces the outgoing ribbon toward the guillotine. The slicing knife can be fixed and the area is often in the form of a "band saw" to make it rotate very slowly on both turrets. Such a slow turn helps to make the cutting knife wear even and keep it cool. After the pellets are cut, the pellets are thrown into a chamber and sprayed along a straight path for cooling due to their own momentum. The pellets are then dried using methods similar to those used for other hot die pelletizers. Granulators
The crushing granulator can reprocess the thermoplastic scrap and granulate the material to a suitable size. Many thermoset plastics and composites manufacturers also use pelletizers to trim and rework.
Today, the use of waste is very important, and environmental protection advocates demand that plastic manufacturers reuse all of their products. Therefore, the manufacturer has no choice but to reprocess the discarded parts and scrap with the granulator. This process can reduce product costs and increase resin utilization. Many municipalities also use pelletizers and shredders to sell plastic scrap to plastic product manufacturers to compensate for the cost of landfill disposal.
The equipment can be designed and manufactured according to the special requirements of the size, shape, quantity and type of plastic scrap. The number and design of the slicing knife, as well as the speed of the granulator, the type of rotor and the size of the screen, are crucial for obtaining high quality scrap recycled articles. The granulator should be placed next to or underneath the plastic machine or placed in the center to handle several plastic machine scraps. Therefore, it is better to choose the granulator reasonably according to the type and position of the scrap to be processed. Depending on the application, such as films, profiles, tubes, and plates, extruders can use machine-side granulators or central granulators.
For automatic injection molding and in-line thermoforming, the use of press-type pelletizers is more common. The sprue residue in the injection molding process falls into the granulator and the product is collected and transported by the conveyor belt to the central area for packaging. The thermoforming granulator is located under the punching machine and removes the remaining material after punching out of the workpiece. The border material enters the granulator and the parts are sent to the packing station. The central granulator generally has a large volume and the motor power is usually 55kw, which is suitable for pipes, films, plates and large parts.
Unlike milled scraps, scraps used for recycling pellets must meet tighter requirements. If the size of the scrap is too large, the throat of the extruder may be clogged, or the melt may be too slow to reduce the amount of extrusion. However, if the size of the scrap is too small, melting will occur too quickly, resulting in thermal degradation. The size of the regrind must be uniform in order to ensure melting at a constant rate within the extruder. Not all thermoplastic scraps can be recycled and pelletized. Some lighter materials, such as thermoformed sheet roll trim, must be compacted by off-line regranulation before it is mixed with other pure resins.
The power of the granulator ranges from 0.37 to 735.5 kw, but their working principles are similar. The cutter mounted on the rotor (approximately 400 to 700 r/min rotation speed) moves relative to the fixed cutter installed outside the cutting stock. The granulator generally has 1 to 6 fixed cutters, depending on the rotor, the number of rotary cutters can reach 32. The granulators used were equipped with a sieve under the fixed cutter. The screen passes the regrind of the desired size and leaves the regrind of large size until they are cut to a sufficiently small size in the cutting chamber.
The granulator's auxiliary equipment includes a muffler (which lowers the noise level to the OSHA requirements), a hopper to prevent backlash from flying back, and a vacuum cleaner. Although the fly-back of the scrap material (the scrap material is returned from the hopper) cannot be completely stopped, the specially designed hopper can minimize the degree of flyback.
Rotor rotor types are open, closed, and spiral. The open type is mainly used for general purposes, closed type for central applications, and spiral type for engineering plastics.
The open rotor sucks the air into the artificial grain compartment, which not only helps clean up the scrap in the cutting compartment, but also transports the scrap to the screen and allows it to pass through. It also cools the granulator. Overheated granulators will soften the plastic causing plugging and product degradation. When the scrap is fed into the granulator by air, an open rotor is usually required to pass the air through the machine. The closed rotor is more robust and therefore it can withstand greater impact loads. Open rotors are generally used for extrusion and injection molding scraps, while closed rotors can be used for central grinding systems and thick cross-sections. Helical rotors and other special rotors, such as a revolving parabolic rotor, combine the robustness of a closed rotor with the air suction action of an open rotor.
When using a pelletizer to handle heavy materials and remove waste, consider the impact of high impact loads on bearings and transmissions. In order to increase the service life of the granulator, most large granulators use 227-681 kg of flywheels to reduce the impact load and reduce the occurrence of failures. Because of the large mass of the enclosed rotor, some flywheel devices are also available.
Knife A typical pelletizer has two or three or five cutters mounted on the rotor and one or two fixed cutters with a 180° mounting angle. However, some models of pelletizers have 30 or more cutters on their rotors. The purpose of the cutter is to ensure uniform stress on the drive and to reduce the frequency of cutter replacement.
Shredding machines In order to extend equipment life and reduce power requirements, many manufacturers use a two-step granulation process to treat recycled large scrap. The first step in the two-step granulation process usually uses a shredder to cut the large scrap into smaller sizes and then feeds the scrap to the granulator. The power required by the shredder is very low compared to a pelletizer of a corresponding size, and the stress problems often encountered by expensive high-power pelletizers in processing large scraps can be avoided.
Recycled film rolls, large extruded profiles and tubes, and difficult-to-treat materials often require the use of a shredder to facilitate pelletizing.
The power required by the granulator is proportional to the amount of extrusion and is exponential to the size of the screen. For example, a pelletizer with a 4.76 mm screen requires 3 times the power of a 9.52 mm screen at the same throughput.
Cold pelletizing system The cold pelletizing system includes a die, a cooling zone (air-cooled or water-cooled), a drying zone (if water-cooled) and a pelletizing chamber. There are two major types of cold pelletizing systems, namely pellet pelletizers and strip pelletizers.
The pellet melter melts the polymer from a mixing apparatus through a belt die or roll mill to a thickness of polymer pellets. The flakes are solidified and cooled by a distance during transportation and then cut into round or square granules with a guillotine knife in one compartment.
Tablet granulation is the oldest method of producing pellets and can be used for various polymers from nylon to polyvinyl chloride.
Heavy weight. It is reported that the accuracy is quite good and the granulation ability can reach 1843.69 kg/h. This is a cold-cut method, and the noise emission is higher than the method of pelletizing from the molten polymer. The life of solidified cutting polymer blades is short, and the generation of powder often becomes a problem. Some "polymer chains" can be seen for some polymers.
The use of strip pelletizers is almost as old as pellet pelletizers. Including die, cooling section (bath or blower), drying section (if water-cooled) and slicing knife. Extruded molten polymer is extruded through a horizontally mounted die using an extruder or gear pump (a modern die is precision machined and uniformly heated to produce a consistent quality bar). After the strip is discharged from the die, it is cooled with a blower or air/vacuum facility or cooled with a water bath. If water cooling is used, the strips must pass through a drying section where they are blown with forced air and the strips are sent to the pelletizing chamber. Using the shear action of a pair of fixed and rotary knives, the strip is precisely cut to the desired length.
The pellets have a diameter of 3.175 mm and a length of 3.175 mm with clear edges and corners.
The traditional method of drawing the strip is to stretch the strip through the cooling section (most commonly a water bath), sometimes causing the strip to fall or inconsistent dimensions. This is most common in polymers with poor strength in the molten state, such as polypropylene, polyester, and nylon. When the strip falls, the material is scrapped, so operators must pay close attention. If the strips are drawn inconsistently, the downstream pellets must be sieved.
Other methods of striping can be monitored without the operator's close attention. The solution is to use a motor-driven slotted feed conveyor to support and divide the strips from the die to the pelletizer. This kind of strip material conveyed by the screw is relatively uniform in size, does not fall down and is therefore less discarded. Some of these methods can have a production capacity of 6803.89 kg/h, compared with about 1814.37 kg/h for the method of stretching into strips, because operators can only watch a limited number of strips.
Strip production line is not costly, easy to operate, and easy to clean. This has advantages for colorant compounding because replacement of two batches of different colorants must thoroughly clean the equipment. However, the defect of the strip forming method is that the cooling section needs to occupy space, and its length is determined according to the temperature requirement of the polymer.
Die surface hot cutting system Die surface hot cutting system has three basic types, namely air flow granulator, water spray (water ring) granulator and underwater granulator. Although this type of system can be designed differently, typical systems include a die, a cutting chamber, an electric rotary blade, a cooling medium, and a method of drying the pellets (if water cooling is used).
The die is an important part of the hot die pelletizing system. It is mounted vertically or horizontally and is usually heated with oil, steam or cartridge or belt heaters. Electric heating is usually used for smaller dies; however, larger dies are usually heated with steam or oil. The die structure materials have different materials, but no matter what kind of material or heating medium is used, the die orifice diameter must be uniform; there must be enough heat to maintain the temperature of the polymer during the entire extrusion process; The rotating mold surface must be tough and smooth - these are necessary to make uniform pellets.
When the molten polymer is extruded through a die, it is cut into pellets using a guillotine knife that rotates at a high rotational speed. The typical situation is a pellet cutter or contact or very close to the die surface. After the pellets are cut off, they are thrown off the knife by centrifugal force and transported to the cooling medium. The size, shape, material, and mounting of the pellet cutter can vary. In some systems, the cutting knife has a spring applied load to automatically adjust the spacing between the cutting knife and the die; some systems must manually adjust the spacing of the cutting knife to the die. Since the life of the cutting knife depends on the accuracy of the alignment of the tool, the abrasiveness of the polymer and the aggressiveness of the operator, it is advisable to cut the polymer pellets in the molten state.
Air flow granulators are recommended for polymers that are sensitive to heat and long residence times, such as polyvinyl chloride, TPR, and crosslinked polyethylene. The pelletizing rate is up to 4989.52 kg/h. The flow path of the polymer from the extruder to the cutting chamber should be kept as short as possible and the minimum amount of heat should be used. When the polymer is extruded through the die, the rotational force of the die surface rotates it into pellets. After the pellets are cut, they are thrown away from the rotary knife and trapped in the air that is forced to circulate in the specially designed cutting chamber. The air stream initially quenches the pellet surface and brings it out of the pelletizing chamber to the cooling zone. Fluid bed dryers are often used to cool pellets. The pellets slide down an adjustable ramp while the circulating fan blows through the pellets. Adjusting the bevel angle can extend or shorten the dwell time of the pellets in the dryer. Another common method of cooling is to discharge the pellets from the cutting chamber into a water bath and remove the water using a fluid bed dryer or a centrifugal dryer.
Water-spray granulators are suitable for most polymers except for polymers with low melt viscosity or stickiness. This type of equipment is also known as a water ring pelletizer. The granulation rate is 13607.77 kg/h.
The molten polymer was extruded from the hot die and cut into pellets by a rotating knife rotating with the die surface. This granule system features a specially designed water jet cutting chamber. The water flows spirally until it flows out of the granule chamber. After the pellets are cut, they are thrown into the water stream for preliminary quenching. Pellet water slurry is further cooled into a pellet slurry tank and then sent to a centrifugal dryer to remove moisture.
The underwater pelletizer is similar to the air pelletizer and the water jet granulator except that it has a steady flow of water through the die surface and is in direct contact with the die surface. The cutting chamber is sized just enough to allow the cutter to rotate freely over the die surface without limiting the flow of water. The molten polymer is extruded from the die, the rotary knife cuts the pellets, and the pellets are brought out of the pelletizing chamber with tempered water and into a centrifugal dryer. In the desiccator, water is drained back to the tank, cooled and recycled; the pellets are removed by a centrifugal dryer.
Underwater pelletizers use a die with uniform heat distribution and special insulation. Small pelletizers use electric heating; large pellet cutters require oil- or steam-heated dies. Process water is normally heated to its maximum temperature, but its heat should not be sufficient to have a detrimental effect on the free flow of the pellets. Underwater pelletizers are used for most polymers, and some models can achieve a pelleting capacity of 22,679.62 kglh. The way water flows through the die face when used for pelleting low viscosity or sticky polymers is a great advantage, but the characteristics of some polymers such as nylon and certain brands of polyester may cause the die to freeze . Other advantages include: because of pelletizing in the molten state, the water plays a role of acoustical barrier and emits less noise; the replacement of the pelletizing knife is less frequently compared to the cold cutting system.
Centrifugal Granulators Centrifugal Granulators Because the die only uses or requires only a minimum amount of heat, rather than a hot die face pelletizer, and because it is a pellet of molten polymer, it is not a cold cut system. Self-contained. The granulator of this type is characterized by the use of a cylindrical die, with the extrusion holes distributed along its circumference. The molten polymer is fed at atmospheric pressure. The extrusion pressure is formed by the depth of the melt on the rotor, the rotor speed, and the relative density of the polymer. As the cylindrical die rotates with its mandrel at a high speed, the centrifugal force acts to evenly flow the molten polymer to the individual orifices on the die. As the polymer exits the extrusion orifice, the rotating die forces the outgoing ribbon toward the guillotine. The slicing knife can be fixed and the area is often in the form of a "band saw" to make it rotate very slowly on both turrets. Such a slow turn helps to make the cutting knife wear even and keep it cool. After the pellets are cut, the pellets are thrown into a chamber and sprayed along a straight path for cooling due to their own momentum. The pellets are then dried using methods similar to those used for other hot die pelletizers. Granulators
The crushing granulator can reprocess the thermoplastic scrap and granulate the material to a suitable size. Many thermoset plastics and composites manufacturers also use pelletizers to trim and rework.
Today, the use of waste is very important, and environmental protection advocates demand that plastic manufacturers reuse all of their products. Therefore, the manufacturer has no choice but to reprocess the discarded parts and scrap with the granulator. This process can reduce product costs and increase resin utilization. Many municipalities also use pelletizers and shredders to sell plastic scrap to plastic product manufacturers to compensate for the cost of landfill disposal.
The equipment can be designed and manufactured according to the special requirements of the size, shape, quantity and type of plastic scrap. The number and design of the slicing knife, as well as the speed of the granulator, the type of rotor and the size of the screen, are crucial for obtaining high quality scrap recycled articles. The granulator should be placed next to or underneath the plastic machine or placed in the center to handle several plastic machine scraps. Therefore, it is better to choose the granulator reasonably according to the type and position of the scrap to be processed. Depending on the application, such as films, profiles, tubes, and plates, extruders can use machine-side granulators or central granulators.
For automatic injection molding and in-line thermoforming, the use of press-type pelletizers is more common. The sprue residue in the injection molding process falls into the granulator and the product is collected and transported by the conveyor belt to the central area for packaging. The thermoforming granulator is located under the punching machine and removes the remaining material after punching out of the workpiece. The border material enters the granulator and the parts are sent to the packing station. The central granulator generally has a large volume and the motor power is usually 55kw, which is suitable for pipes, films, plates and large parts.
Unlike milled scraps, scraps used for recycling pellets must meet tighter requirements. If the size of the scrap is too large, the throat of the extruder may be clogged, or the melt may be too slow to reduce the amount of extrusion. However, if the size of the scrap is too small, melting will occur too quickly, resulting in thermal degradation. The size of the regrind must be uniform in order to ensure melting at a constant rate within the extruder. Not all thermoplastic scraps can be recycled and pelletized. Some lighter materials, such as thermoformed sheet roll trim, must be compacted by off-line regranulation before it is mixed with other pure resins.
The power of the granulator ranges from 0.37 to 735.5 kw, but their working principles are similar. The cutter mounted on the rotor (approximately 400 to 700 r/min rotation speed) moves relative to the fixed cutter installed outside the cutting stock. The granulator generally has 1 to 6 fixed cutters, depending on the rotor, the number of rotary cutters can reach 32. The granulators used were equipped with a sieve under the fixed cutter. The screen passes the regrind of the desired size and leaves the regrind of large size until they are cut to a sufficiently small size in the cutting chamber.
The granulator's auxiliary equipment includes a muffler (which lowers the noise level to the OSHA requirements), a hopper to prevent backlash from flying back, and a vacuum cleaner. Although the fly-back of the scrap material (the scrap material is returned from the hopper) cannot be completely stopped, the specially designed hopper can minimize the degree of flyback.
Rotor rotor types are open, closed, and spiral. The open type is mainly used for general purposes, closed type for central applications, and spiral type for engineering plastics.
The open rotor sucks the air into the artificial grain compartment, which not only helps clean up the scrap in the cutting compartment, but also transports the scrap to the screen and allows it to pass through. It also cools the granulator. Overheated granulators will soften the plastic causing plugging and product degradation. When the scrap is fed into the granulator by air, an open rotor is usually required to pass the air through the machine. The closed rotor is more robust and therefore it can withstand greater impact loads. Open rotors are generally used for extrusion and injection molding scraps, while closed rotors can be used for central grinding systems and thick cross-sections. Helical rotors and other special rotors, such as a revolving parabolic rotor, combine the robustness of a closed rotor with the air suction action of an open rotor.
When using a pelletizer to handle heavy materials and remove waste, consider the impact of high impact loads on bearings and transmissions. In order to increase the service life of the granulator, most large granulators use 227-681 kg of flywheels to reduce the impact load and reduce the occurrence of failures. Because of the large mass of the enclosed rotor, some flywheel devices are also available.
Knife A typical pelletizer has two or three or five cutters mounted on the rotor and one or two fixed cutters with a 180° mounting angle. However, some models of pelletizers have 30 or more cutters on their rotors. The purpose of the cutter is to ensure uniform stress on the drive and to reduce the frequency of cutter replacement.
Shredding machines In order to extend equipment life and reduce power requirements, many manufacturers use a two-step granulation process to treat recycled large scrap. The first step in the two-step granulation process usually uses a shredder to cut the large scrap into smaller sizes and then feeds the scrap to the granulator. The power required by the shredder is very low compared to a pelletizer of a corresponding size, and the stress problems often encountered by expensive high-power pelletizers in processing large scraps can be avoided.
Recycled film rolls, large extruded profiles and tubes, and difficult-to-treat materials often require the use of a shredder to facilitate pelletizing.
The power required by the granulator is proportional to the amount of extrusion and is exponential to the size of the screen. For example, a pelletizer with a 4.76 mm screen requires 3 times the power of a 9.52 mm screen at the same throughput.
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