Views: 0 Author: Site Editor Publish Time: 2022-11-21 Origin: Site
In a basic technical definition, plastic extruder it is the transformation of solid plastic mass converted into a shape. Plastic extrusion is a mass manufacturing process. The raw plastic is about to melt and form a continuous outline.
The basic principle of the plastic extrusion machine
The polymer is molten and pounded and is introduced into the die shell with a constant flow source, temperature control, and a constant turntable speed, and the molten commodity state of the type blank is produced according to the die shell. However, the single-screw extruder Extruder and single-screw extruder structure and principles are different, and their operation and processing standards are also different.
Structure of extruder
In the whole process of plastic extrusion, the plastic is conveyed, compacted, and further melted with the help of an extruder, then extruded from the die under working pressure, molded by molding machinery and equipment, and cooled to make the desired product.
Therefore, the extruder is the leading equipment for plastic extrusion, which determines the quality and output of the extruded products. The extruder consists of an extruder screw, barrel, heating and cooling system, transmission device, and control device. Among them, the extruder screw is an integral part of the extruder. It plays a vital role in the extrusion process, such as conveying, compacting, melting, homogenizing, filling, and pumping raw materials.
The efficacy of each section of the extruder
A typical single-screw extruder Extruder has three stages: feeding, deceleration, and extrusion.
1. Feeding section: extrusion molding generally uses granular materials. The feeding device is a device to ensure continuous feeding to the barrel of the extruder, similar in shape to a Brinell funnel, with two types of cone and square cone, also called hopper. Its bottom end is connected to the barrel and has a feeding port equipped with a disconnecting device to adjust and disconnect the material flow. A refrigeration chuck is provided around the feeding port to prevent the high temperature of the feeding from transferring heat into the hopper and to prevent the plastic in the hopper from becoming sticky when the temperature rises, causing uneven feeding and blocking the feeding process. The hopper has laminated glass viewing holes on the side and a calibration and metering check device. Some hoppers also have a decompression device that heats and dries the vacuum pump to prevent plastic from digesting and absorbing water from the air, and they contain stirring devices to overcome "railroad bridges" caused by powdered plastic, as well as fully automatic feeding devices that allow for periodic quantitative analysis.
2. Shrinkage section: The barrel, a metal drum under heat and pressure. The melting and shrinking of the raw material take place in the barrel. The operating temperature during extrusion is generally 180~290℃, and the internal pressure of the barrel reaches 60MPa. A heating and cooling device is set outside the charging barrel, which generally divides the heating into three or four sections. Common resistance or inductive electric heaters also use far heat radiation. The purpose of cooling is to avoid over-temperature or fast cooling plastic when parking to prevent plastic dissolution. Air cooling or water cooling is generally used for cooling. The gun barrel must be subjected to high pressure and requires sufficient compressive strength and bending stiffness with a clean inner cavity. The barrel is generally made of inches of wear and corrosion-resistant plastic friction so that the plastic superheat. In addition, the surface temperature of the extruder screw slightly lower barrel can prevent the raw materials from sticking to it, which is conducive to transporting raw materials.
3. Extrusion section: The extruder screw is suspended in the middle of the barrel by a thrust bearing, which is in line with the axis of the barrel without obvious error. The clearance between the extruder screw and the barrel is not large, which makes the plastic melt and push forward due to the solid cutting effect.
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