What Is Crowding Out?
It is also called extrusion molding or extrusion in plastic processing, and it is also called extrusion in rubber processing. It refers to a processing method in which materials pass through the action between the barrel of the extruder and the screw, are plasticized under heat, are pushed forward by the screw, and are continuously passed through the head to make various cross-section products or semi-products.
- Chinese name
- Squeeze out
- Foreign name
- extrusion
- Pinyin
- jch
- nickname
- Extrusion or extrusion
- It is also called extrusion molding or extrusion in plastic processing, and it is also called extrusion in rubber processing. It refers to a processing method in which materials pass through the action between the barrel of the extruder and the screw, are plasticized under heat, are pushed forward by the screw, and are continuously passed through the head to make various cross-section products or semi-products.
Squeeze out word definitions
- Extruders are also used in the chemical fiber industry to feed spinnerets for melt spinning. Extrusion is used for the addition of thermoplastics and rubber
- Squeeze out
Extrusion equipment
- The main body is the extruder and head, in addition to auxiliary equipment such as feeding, shaping, cooling, traction, cutting and winding (see color picture). In rubber processing, vulcanization equipment is also included. In actual production, the main body and auxiliary equipment are often connected into a unit.
- Extruder
- Single screw extruder and twin screw extruder according to the number of screws
- Single screw extruder
- The single screw extruder is equipped with a rotating screw in a heating cylinder. The cylinder is equipped with a heating and cooling device on the outer partition. One end has a radial feeding port and the other end is axially connected to the head. The screw is a key component of the extruder. The main technical parameters of single screw extruder are screw diameter, aspect ratio (ratio of screw length to diameter), screw speed range, drive motor power, barrel heating power and machine production capacity. The diameter of the screw determines the production capacity of the extruder and the maximum cross-section of the product. Different materials require different geometries of screw and aspect ratio. Modern plastic extruders widely use combined screws, distribution mixing screws, and adding barriers or pins on the screws to improve plasticization, production capacity and product quality [2] .
- Twin screw extruder
- The twin-screw extruder has two screws rotating in an -shaped heating barrel. The screw can be divided into meshing and non-meshing types; combined and non-combined; co-rotating and non-rotating. It is more commonly used in the same-mesh type and the different-mesh type. The former is used for plastic blending, filling and reinforcement to produce various batches; the latter is used for processing rigid polyvinyl chloride products.
- Head and die
- The die head and die are located at the front end of the barrel, which is the warm flow and modeling part of the extruder. By changing the die head and the die shape, semi-finished products of different specifications and shapes can be extruded [3] .
- (1) The machine head is located at the front of the fuselage and is installed between the end of the screw and the mouth. The function of the machine head is to change the rubber material from the state of screw movement to the state of linear movement, while forming the necessary pressure and a certain shape of the semi-finished product.
- (2) The mouth shape is located at the front of the machine head, which is used to shape the semi-finished product and control its size. By changing the mouth shape, one extruder can prepare semi-finished products with different specifications and shapes. The requirement for the mouth shape is to work hard to ensure that the rubber material is laminar, without dead spots, and strive to minimize the pressure drop. The mouth shape mainly includes ordinary mouth shape and special mouth shape.
- There are two types of common mouth shapes: one is a steel plate with a certain geometric shape, which is used to extrude solid and sheet-shaped semi-finished products, such as treads, rubber strips, and rubber sheets; the other is composed of mouth shape, core shape, and core. Composed of type bearings, used for extruding hollow semi-finished products, such as inner tubes and hoses.
- Special lip shapes are mainly double-roller head lip shapes and orientation lip shapes, which are a new type of lip design.
Extrusion process
- Generally, according to the type of polymer processed and the shape of the product or semi-finished product, the extruder, head and die, as well as corresponding auxiliary devices such as shaping and traction are selected, and then the extrusion process conditions such as screw speed and head pressure , Material temperature, and setting temperature, traction speed, etc. In the extrusion process, the materials are generally plasticized, but the shaping method is different. For example, extruded plastics often need to be cooled and shaped to solidify them, while semi-finished products of extruded rubber need further vulcanization. Using different extrusion equipment and processes, different products can be obtained.
- 1.Pellet
- After the polymer is mixed with various additives, it is sent to the extruder to be melted, and further mixed uniformly. Through the porous die, a plurality of strips are formed, and then cut into pellets. The cut is divided into hot and cold pellets. After the former strip leaves the die, it is immediately cut with a rotary knife while cooling with air or water. The latter is to cool all the strips and feed them to the pelletizer for pelletizing.
- 2.Pipe
- The material passes through a ring-shaped space composed of a die and a core mold to form a tube, and then is shaped and cooled to obtain a tube with a smooth surface, accurate size and geometric shape. The commonly used shaping method is to use outer diameter shaping, that is, the extruded tubular material passes through a shaping sleeve with the same inner diameter as the outer diameter of the product, and the pressure is used to make the tubular material close to the inner wall of the shaping sleeve, so as to obtain a pipe with an accurate outer diameter. In order to cause a pressure difference, compressed air can be introduced into the tube, and negative pressure can also be caused outside the tube.
- Sheets and films
- Flat products with a thickness of more than 0.25mm and a length greater than the width are called sheets; those with a thickness of less than 0.25mm are called films. For example, the film formed by the flat die is cooled and shaped by a cooling drum with a very smooth surface, and a flat film can be obtained. This method is also called extrusion casting method. This is a common method for making polypropylene films. If the obtained flat film is fed into a tenter and stretched 4 to 10 times simultaneously in the longitudinal and transverse directions (or longitudinal stretching and then transverse stretching), a biaxially oriented film can be obtained. Because the macromolecules are oriented during stretching, the strength of the film is high, but the water permeability and air permeability are reduced. Commonly used in the manufacture of polypropylene and polyester films. If foaming agent is added to the material, and special screw and die are used, low-foam plastic sheet can also be made.
- 4. Covering line
- When the bare metal wire passes through a T-shaped die, the molten plastic forms a covering layer around the bare wire. After the covered wire is cooled and wound, various wire and cable products are obtained.
- 5, blown film
- Most films are made by inflation. In this method, the tube-shaped object blown out from the die is blown with compressed air, and the formed bubble is cooled by the air blown by the wind ring, and then led out by the guide roller (or plywood), and then wound into a roll to obtain a blow. Plastic film. A large number of packaging bags and agricultural films are made into cylindrical films by this method, and then further welded and cut to make them.
- 6. Composite products
- Several extruders are used to supply several plastics at the same time, which are then extruded through a common die to form an integrated composite product. For example, coextrusion with three plastics A, B and C can produce various composite films, composite sheets, plates, profiles and pipes.
- 7, rubber filtration
- In the manufacture of thin-walled rubber products, in order to prevent air leakage and water leakage from the product, the rubber compound must not contain impurities. Generally, the rubber compound is filtered with an extruder before the vulcanizing agent is added, that is, one or more layers of filter screens are placed at the head. To filter out impurities in the plasticized material.
- 8.Tire tread and inner tube manufacturing
- The tread is extruded as a whole or in layers. For the overall extrusion, one extruder can be used to extrude a rubber compound through a flat die; it can also be co-extruded by two extruder with two rubber compounds (tire crown material and sidewall material). The inside of the head is combined into a whole tread. For layered extrusion, two extruders are used to extrude the two rubber compounds into the tire crown and the sidewall, respectively, and then heat-laminated on the conveyor belt, and then rolled into a whole by multi-disk flexible rolling. Tube extrusion is similar to tube extrusion. After the tire tube is extruded, it is cut and then jointed.
- 9.Melt spinning
- Some melted resins are usually melted by an extruder when melt spinning. The melted material directly enters the spinneret through the filter, or is driven into the spinneret by a spinneret pump.
Extrusion stability control system
- Features of extrusion die temperature machine:
- Pipeline explosion-proof device
- Air blowback function (optional)
- Return water temperature display table
- Automatic exhaust function at startup
- Heating power switching function
- Instant cooling shutdown function
- Isolated electrical control box. Extend the life of electrical appliances
- RS485 communication function for automatic management. (Optional)
- Hot water BY-PASS pressure relief circuit
- Multi-point temperature control unit can be customized
- Pump horsepower and heating power can be customized
- Appliances use OMRON. FUJI. TE. LG. MOELLER. ABB. WEST.
- Temperature control range: Inlet water temperature + 15 120
- 304 stainless steel integrated pipeline, reducing pipe resistance and rust
- Control method: Imported microcomputer or (optional) PLC control
- Complete safety protection, fault display, repair. No professional required for maintenance
- Machine specifications
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