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Company ProfileShaanxi Kunlan Cable Manufacturing Co., Ltd. is a modern professional wire and cable manufacturing enterprise integrating R&D, production, sales and service, with a professional technical R&D team, production team and marketing team.
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Product CenterThe company specializes in producing a variety of "ShanKunLan" brand wires and cables. Main products include: various installation wires, plastic insulated power cables, control cables, cross-linked cables, overhead insulated cables, parallel bundled cables, pre-branched cables, rubber sheathed cables, flame-retardant cables, fire-resistant cables, low-smoke halogen-free cables, and radiation-resistant cables, etc. We can also design and produce various special cables according to customer needs.
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TechnicalThe company boasts a team of professional R&D personnel and skilled industrial workers. It has established a first-class corporate technology R&D center and relies on renowned domestic research institutions such as Shanghai Cable Research Institute, Xi'an Jiaotong University, and Harbin Institute of Technology for technical support. Its strong technical capabilities provide powerful support for product quality control and improvement, as well as new product development.
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BlogThe company boasts a team of professional R&D personnel and skilled industrial workers. It has established a first-class corporate technology R&D center and relies on renowned domestic research institutions such as Shanghai Cable Research Institute, Xi'an Jiaotong University, and Harbin Institute of Technology for technical support. Its strong technical capabilities provide powerful support for product quality control and improvement, as well as new product development.
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RecruitmentThe company boasts a team of professional R&D personnel and skilled industrial workers. It has established a first-class corporate technology R&D center and relies on renowned domestic research institutions such as Shanghai Cable Research Institute, Xi'an Jiaotong University, and Harbin Institute of Technology for technical support. Its strong technical capabilities provide powerful support for product quality control and improvement, as well as new product development.
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Online mallThe company boasts a team of professional R&D personnel and skilled industrial workers. It has established a first-class corporate technology R&D center and relies on renowned domestic research institutions such as Shanghai Cable Research Institute, Xi'an Jiaotong University, and Harbin Institute of Technology for technical support. Its strong technical capabilities provide powerful support for product quality control and improvement, as well as new product development.
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Knowledge sharing on the extrusion process of wires and cables
Knowledge sharing on the extrusion process of wires and cables
Publish Time:
2025-05-08
Source:
The main insulating and sheathing materials for plastic wires and cables are plastics. Thermoplastic plastics have superior properties and good processing performance
The main insulating and sheathing materials for plastic wires and cables are plastics. Thermoplastics have superior properties and good processing performance, especially for the simple process of extruding insulation and sheathing for wires and cables. The basic method for producing plastic insulation and sheathing for wires and cables is continuous extrusion using a single-screw extruder. Because extruders have the characteristic of continuous extrusion, the production process of plastic insulation and sheathing is also continuous.
In terms of wire and cable production, differences in product specifications and extrusion components often determine certain changes in extrusion equipment and process parameters. However, in general, the extrusion and coating processes for various products and components are similar. The following is a summary of information on extrusion principles, processes, and die types compiled from the internet for your reference.
1 PART
Basic Principles of Plastic Extrusion
The working principle of an extruder is: using a screw of a specific shape, rotating in a heated barrel, to extrude the plastic fed from the hopper forward, making the plastic uniformly plasticized (i.e., melted), and through the die head and dies of different shapes, extruding the plastic into continuous plastic layers of various required shapes, wrapping around the core wire and cable.
1. Plastic Extrusion Process
The plastic insulation and sheathing of wires and cables are produced using continuous extrusion, generally using a single-screw extruder.
2. Three Stages of the Extrusion Process
The most important basis for plastic extrusion is the plasticity of the plastic. The process of plastic forming in an extruder is a complex physical process, including mixing, breaking, melting, plasticizing, degassing, compacting, and finally shaping and setting.
The first stage is the plasticization stage, also known as the compression stage. It is completed in the extruder barrel, and through the rotation of the screw, the plastic changes from a granular solid to a plastic viscous fluid.
The second stage is the forming stage. It takes place in the die head. Due to the rotation and pressure of the screw, the viscous fluid is pushed to the die head, and through the die in the die head, the viscous fluid is formed into the required size and shape of the extruded coating material, and coated on the core wire or conductor.
The third stage is the setting stage. It is carried out in a cooling tank or cooling pipe. After cooling, the extruded plastic layer changes from an amorphous plastic state to a fixed solid state.
3. Changes in Plastic Flow during the Plasticization Stage
In the plasticization stage, during the movement of the plastic along the screw axis towards the die head, it undergoes changes in temperature, pressure, viscosity, and even chemical structure. These changes are different in different sections of the screw.
In the feeding section, the first step is to provide a softening temperature for the granular solid plastic, and then the shear stress generated between the rotating screw and the fixed barrel acts on the plastic particles to break up the softened plastic.
In the melting section, the broken, softened, and preliminarily mixed solid plastic moves towards the die head along the screw channel due to the pushing action of the screw, entering the melting section from the feeding section.
In the homogenization section, there are several prominent process characteristics: the screw thread depth in this section is the shallowest, that is, the screw channel volume is the smallest, so this is the working section where the pressure between the screw and the barrel is the greatest.
4. Flow State of Plastics during Extrusion
During the extrusion process, the rotation of the screw pushes the plastic, while the barrel is stationary. This creates relative motion between the barrel and the screw, and this relative motion creates friction on the plastic, causing the plastic to be dragged forward.
1) Forward flow - refers to the flow of plastic along the screw channel towards the die head. It is generated by the pushing force of the screw rotation and is the most important of the four flow forms.
2) Reverse flow - also known as backflow, its direction is exactly opposite to the direction of forward flow.
3) Transverse flow - it is the flow of plastic along the axial direction, that is, perpendicular to the screw channel.
4) Leakage flow - it is also generated by the resistance of the die, screen, and filter in the die head. However, it is not the flow in the screw channel, but the reverse flow formed in the gap between the screw and the barrel.
The four flow states of plastic do not appear in isolation. For a certain plastic particle, there is neither true reverse flow nor closed circulation. The actual flow of the melt plastic in the screw channel is a combination of the above four flow states, a forward flow in a spiral trajectory.
5. Extrusion Quality
Extrusion quality mainly refers to whether the plasticization of the plastic is good and whether the geometric dimensions are uniform, that is, whether the radial thickness is consistent and whether the axial outer diameter is uniform. In addition to the plastic itself, the factors determining the plasticization situation are mainly temperature, shear strain rate, and action time.
Under the condition of ensuring the required extrusion amount, the screw channel depth can be increased by increasing the speed. In addition, the gap between the screw and the barrel also affects the extrusion quality. When the gap is too large, the reverse flow and leakage flow of the plastic increase, not only causing extrusion pressure fluctuations and affecting the extrusion amount, but also causing the plastic to overheat due to the increase in these backflows, leading to plastic scorching or difficult forming.
2 PART
Operating Procedures for Plastic Extruders
A plastic extrusion unit consists of an extruder (main machine) and multiple auxiliary equipment. During production, the unit personnel should cooperate closely. Operators must be familiar with the growth process and operating procedures.
1. Extrusion Process of Plastic Extruder
A plastic extruder is a hot extrusion device. The coiled cable or cable core is placed on the payout device and ensures a certain tension. After passing through the tension straightening device, it enters the extruder head to extrude the insulation layer or sheath layer.
Plastic pellets are fed into the extruder barrel via a hopper. The rotating screw conveys the pellets into the barrel where they are heated and mixed, promoting plasticization. The screw then pushes the plasticized plastic towards the die head, extruding a continuous, tight sheath around the wire or cable core.
To control the thickness of the plastic layer and extrusion pressure, the annular gap between the core and sleeve of the die should be adjusted to ensure a uniform plastic layer.
Select appropriate dies according to the process-specified control temperature. Regularly monitor changes in the heating system, outer diameter, and speed to prevent phenomena such as plastic layer eccentricity, burning, and poor plasticization.
Keywords:
Insulating material,eccentricity
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