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2025
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The “heart” of the sheet extrusion machine: The critical roles of the extruder and melt pump
Author:
In the field of plastic processing, sheet extruders are essential equipment for producing various types of plastic sheets. Among the components of this equipment, the extruder and the melt pump are undoubtedly two indispensable key parts. Today, let’s take a closer look at the role and operating principle of the extruder—the “heart” of the sheet extruder—as well as the critical importance of the melt pump in the melting process.
The “heart” of the sheet extruder: The function and principle of the extruder
The extruder is the core component of a sheet extrusion machine. Its primary function is to heat and melt plastic pellets into a uniform melt, which is then extruded through the die head to form the desired sheet. The operating principle of the extruder can be summarized in the following steps:
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Raw material conveying Plastic pellets enter the barrel of the extruder through the feed port.
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Heat and melt In the料筒, plastic pellets are heated to a molten state, forming a flowing melt.
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Mixing and Plasticization Through the rotation and shearing action of the screw, the melt is thoroughly mixed and plasticized, ensuring its uniformity.
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Melt conveyance The melt is extruded through the die to form the desired sheet shape.
The performance of the extruder directly affects the quality and production efficiency of the sheet material. Therefore, it is hailed as the “heart” of the sheet-making machine.
Melt Pump: The Extruder’s “Powerful Assistant”
During the melting process in sheet extruders, melt pumps play a crucial role. The primary function of a melt pump is to stabilize the pressure and flow rate of the melt, ensuring uniformity and stability throughout the melt’s transportation. Below are several key functions of melt pumps:
①、 Stabilize pressure The melt pump can adjust the unstable melt pressure coming from the extruder, ensuring that the melt is delivered to the die at a stable pressure. This is crucial for maintaining uniform thickness of the sheet.
②、 Precise measurement The melt pump can achieve nearly linear flow output, is easy to control, and enables precise regulation of the melt flow rate according to production needs, ensuring uniform thickness and accurate dimensions of the extruded sheet.
③、 Improve product quality By providing stable pressure and flow output, melt pumps can reduce production interruptions and the generation of defective products caused by factors such as pressure fluctuations, thereby improving the quality of sheets and production efficiency.
④、 Reduce energy consumption The melt pump transfers the decompression function of the extruder to a gear pump, enabling the extruder to operate at low pressure and low temperature. This reduces leakage flow and increases production output.
So, what would be the impact if a melt pump isn't installed?
①、 Unstable pressure Factors such as variations in the screw speed of the extruder, differences in material viscosity, and uneven feeding can all lead to fluctuations in melt pressure. This pressure instability directly affects the uniformity of sheet thickness, causing local areas of the sheet to become thicker or thinner, thereby compromising product quality.
②、 Inaccurate traffic control Without a melt pump, controlling the melt flow rate becomes difficult, making it hard to ensure uniform sheet thickness and precise dimensions. This could result in sheets that are either too thick or too thin, not only wasting material but also potentially compromising the physical properties of the product.
③、 Product quality has declined. Due to the instability of pressure and flow, it is difficult to ensure uniform thickness and dimensional accuracy of the sheet, thereby reducing the overall quality of the product. Moreover, the absence of a melt pump may also lead to patterns, waviness, or streak-like defects on the sheet surface, affecting both the appearance and performance of the product.
④、 Reduced production efficiency: A melt pump, by providing stable pressure and flow output, can enhance production efficiency. Without a melt pump, the extruder may need to operate at higher pressures, which not only increases energy consumption but also risks overloading the equipment. Moreover, due to unstable product quality, the defect rate may rise, further reducing production efficiency.
⑤、 Shortened equipment lifespan: Without a melt pump, the extruder needs to operate at higher pressures, which increases wear on the screw and barrel. In the long run, this can shorten the equipment’s lifespan and raise the costs of maintenance and replacement.
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