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1. Single-screw extruder structure
The structure of single-screw extruder is shown in Fig. 2-2. It mainly consists of five major parts: extrusion plasticising system, transmission system, material supply system, heating and cooling system and control system.
Structure of single-screw extruder
1-connecting mould flange 2-diverter plate 3-screw 4-cooling water pipe 5-heater 6-barrel 7-gear pump 8,10-motor 9-roller bearing 11-feed hopper 12-gear reducer 13-rotary joint 14-V-belt pulley 15-main motor 16-reducer body 17-body 18-safety cover
2. Extrusion plasticising system
The plasticising system of the extruder is the main part of the extruder equipment. Its function is to transform the raw material from solid state to plasticised molten state by extrusion and heating, and then extrude it evenly from the manifold (also called porous plate) at the front end of the barrel in equal quantity and pressure into the mould of the moulded products.
(1)Screw
1) Structure of screw.
Screw is an important part of the extruder, its diameter size on behalf of the specifications of the extruder; the choice of its structural type of application is to ensure that the plastic resin plasticising quality of one of the main conditions. Commonly used screw structure type has a gradual change screw and mutation screw.
Commonly used screw structure type
a) Gradual-change screw b) Mutant screw
The structural characteristics of the variable screw are that the pitch of the threaded part of the screw is equal, and the depth of the threaded groove gradually becomes shallower and deeper from the charging section to the homogenising section. There is also a gradual change screw, the depth of the threaded groove in the charging section and homogenising section remains unchanged, while the depth of the threaded groove in the plasticising section gradually becomes shallower from deeper. This type of screw structure is suitable for extrusion plasticisation of non-crystalline plastics such as PVC.
The depth of the threaded groove in the charging section and homogenising section of the mutant screw remains unchanged, while the length of the plasticising section (also called the compression section) of the screw is very short, and the depth of the threaded groove in this section suddenly changes from deep to shallow. This screw structure is suitable for extrusion moulding of crystalline plastics such as polyolefin.
¢Ù Screw diameter.
It is the diameter of the outer circle of the threaded part of the screw, which is expressed by D and the unit is mm. The diameter of the screw can indicate both the specification size of the extruder and the size of the specification size of the plastic products produced by the extruder.
¢Ú length-diameter ratio.
It refers to the ratio of the length of the threaded part of the screw to the diameter, i.e. L/D.JB/T 8061-2011 standard specifies that the L/D ratio of the screw (20~30):1 range. In general, the screw for extrusion plasticisation of non-crystalline plastics such as polyvinyl chloride, the L/D ratio is within the range of (20~25):1; the screw for extrusion plasticisation of polyolefin plastics, the L/D ratio is taken to be within the range of (25~30):1. Extruding plasticising raw materials, take the big value of L/D ratio, is conducive to the plasticising of raw materials, can improve the working speed of the screw, then can improve the output of the extruder; however, too big L/D ratio will make the screw length increase, which brings more difficulties to the screw cutting and heat treatment.
¢ÛSegmentation of the threaded part.
According to the functional role of the screw rotation, the threaded part is divided into feeding section L1, plasticising section L2 and homogenising section L3, feeding section accepts hopper feed, with the rotation of the screw, the raw material is transported to the plasticising section.
Nanjing Suminoe Precision Machinery Co., Ltd.[1] is a collection of scientific research, production, sales in one of the high-tech enterprises, and has always adhered to the integrity of the business philosophy of equality, the interests of the customer first, in order to better improve the quality of the equipment, into a more professional and standardised production track. We set up an independent R & D technology centre and production department for six major types of equipment, such as plastic sheet and plate, casting, bi-directional stretching, non-woven non-woven meltblown cloth, film lamination and renewable granulation environmental protection recycling system. Provide professional full set of technical solutions to meet the special needs of each customer.
The structure of single-screw extruder is shown in Fig. 2-2. It mainly consists of five major parts: extrusion plasticising system, transmission system, material supply system, heating and cooling system and control system.
Structure of single-screw extruder
1-connecting mould flange 2-diverter plate 3-screw 4-cooling water pipe 5-heater 6-barrel 7-gear pump 8,10-motor 9-roller bearing 11-feed hopper 12-gear reducer 13-rotary joint 14-V-belt pulley 15-main motor 16-reducer body 17-body 18-safety cover
2. Extrusion plasticising system
The plasticising system of the extruder is the main part of the extruder equipment. Its function is to transform the raw material from solid state to plasticised molten state by extrusion and heating, and then extrude it evenly from the manifold (also called porous plate) at the front end of the barrel in equal quantity and pressure into the mould of the moulded products.
(1)Screw
1) Structure of screw.
Screw is an important part of the extruder, its diameter size on behalf of the specifications of the extruder; the choice of its structural type of application is to ensure that the plastic resin plasticising quality of one of the main conditions. Commonly used screw structure type has a gradual change screw and mutation screw.
Commonly used screw structure type
a) Gradual-change screw b) Mutant screw
The structural characteristics of the variable screw are that the pitch of the threaded part of the screw is equal, and the depth of the threaded groove gradually becomes shallower and deeper from the charging section to the homogenising section. There is also a gradual change screw, the depth of the threaded groove in the charging section and homogenising section remains unchanged, while the depth of the threaded groove in the plasticising section gradually becomes shallower from deeper. This type of screw structure is suitable for extrusion plasticisation of non-crystalline plastics such as PVC.
The depth of the threaded groove in the charging section and homogenising section of the mutant screw remains unchanged, while the length of the plasticising section (also called the compression section) of the screw is very short, and the depth of the threaded groove in this section suddenly changes from deep to shallow. This screw structure is suitable for extrusion moulding of crystalline plastics such as polyolefin.
¢Ù Screw diameter.
It is the diameter of the outer circle of the threaded part of the screw, which is expressed by D and the unit is mm. The diameter of the screw can indicate both the specification size of the extruder and the size of the specification size of the plastic products produced by the extruder.
¢Ú length-diameter ratio.
It refers to the ratio of the length of the threaded part of the screw to the diameter, i.e. L/D.JB/T 8061-2011 standard specifies that the L/D ratio of the screw (20~30):1 range. In general, the screw for extrusion plasticisation of non-crystalline plastics such as polyvinyl chloride, the L/D ratio is within the range of (20~25):1; the screw for extrusion plasticisation of polyolefin plastics, the L/D ratio is taken to be within the range of (25~30):1. Extruding plasticising raw materials, take the big value of L/D ratio, is conducive to the plasticising of raw materials, can improve the working speed of the screw, then can improve the output of the extruder; however, too big L/D ratio will make the screw length increase, which brings more difficulties to the screw cutting and heat treatment.
¢ÛSegmentation of the threaded part.
According to the functional role of the screw rotation, the threaded part is divided into feeding section L1, plasticising section L2 and homogenising section L3, feeding section accepts hopper feed, with the rotation of the screw, the raw material is transported to the plasticising section.
Nanjing Suminoe Precision Machinery Co., Ltd.[1] is a collection of scientific research, production, sales in one of the high-tech enterprises, and has always adhered to the integrity of the business philosophy of equality, the interests of the customer first, in order to better improve the quality of the equipment, into a more professional and standardised production track. We set up an independent R & D technology centre and production department for six major types of equipment, such as plastic sheet and plate, casting, bi-directional stretching, non-woven non-woven meltblown cloth, film lamination and renewable granulation environmental protection recycling system. Provide professional full set of technical solutions to meet the special needs of each customer.