What are the types of filter mesh?
Extruder filter mesh can be classified from multiple dimensions such as shape, material, weaving process, structure, and precision to suit different equipment and process requirements. The main classification methods are as follows:
By shape: adapting to different equipment interfaces
The shape of the filter mesh must fit tightly against the breaker plate inside the extruder to prevent material leakage. Common shapes include:
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Round: The most common standard shape, suitable for most single-screw and twin-screw extruders.
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Square/Rectangular: Commonly found in some specific designs or large extrusion systems.
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Oval/Waist-shaped: Often used in equipment requiring specific fluid channels.
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Annular: A hollow ring structure, specially used for special filtration components in chemical fiber, film, and other fields.
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Cap-shaped/Special-shaped: Customized shapes to meet special installation or filtration requirements.
In addition, there are special shapes such as kidney-shaped. They can also be divided into single-layer, double-layer, and multi-layer by the number of layers to meet different strength or precision combinations.
By material: dealing with different materials and working conditions
Material selection directly determines the corrosion resistance, temperature resistance, and applicable scenarios of the filter mesh.
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Stainless steel: The most commonly used material. Main grades are 304 and 316/316L. 316L, due to its excellent acid and alkali corrosion resistance, is an ideal choice for high-end applications such as food and medical.
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Special alloys: Used for extreme conditions. For example, nickel-based alloys resist corrosion from fluoropolymers or PVDC; titanium alloys are suitable for highly corrosive seawater or chemical environments.
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Black wire cloth: Made of low-carbon steel wire, low cost, high hardness, suitable for coarse filtration of general plastics.
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Other metals: Such as galvanized mesh, copper mesh, etc., used for specific needs.
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Special types: Sintered metal mesh is sintered from multiple layers of metal mesh, offering high strength, high precision, long life, and can be backwashed and regenerated. Wedge wire mesh is wound from wedge-shaped wires, with uniform gaps and not easily clogged, especially suitable for melts with high impurity content.
By weaving process: affecting filtration precision and method
The weaving method determines the filtration mechanism and structural stability of the filter mesh.
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Plain weave: The most basic and commonly used weaving method. Warp and weft wires alternately interweave over and under one another, providing stable structure and high strength, suitable for most conventional filtration.
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Twill weave: Warp and weft wires interweave in a pattern of two over two under or three over three under, resulting in clearer openings, good permeability, and a smoother surface, suitable for applications requiring slightly higher filtration precision.
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Dutch weave: A dense weave with fine warp and coarse weft, forming a unique “non-straight-through” flow path, offering extremely high filtration precision and effectively capturing fine particles, often used for fine filtration.
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Other weaves: Also include herringbone weave, Dutch weave (also known as “Dutch weave”), etc., all variations of the above basic weaves to achieve specific filtration performance.
By mesh count/precision: determining filtration coarseness
Mesh count is the core indicator of filter mesh fineness, referring to the number of openings per square inch. The higher the mesh count, the smaller the openings, and the higher the filtration precision.
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Coarse filter mesh (20 mesh): Used for filtering larger particles or as a support layer, low resistance, suitable for rough processing with low impurity requirements.
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Medium filter mesh (40–60 mesh): The most widely used range, effectively removing common impurities while balancing filtration effect and output.
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Fine filter mesh (80–150 mesh): Used for producing high-quality films, optical fibers, etc., capable of removing tiny gels or impurities, but with high resistance and easy clogging.
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Ultra-fine filter mesh (200–800 mesh): Used for high-end applications such as chemical fiber spinning, requiring special weaving processes (e.g., Dutch weave), capable of filtering micron-sized particles.
By product form: adapting to different screen changing methods
According to the usage method, there are two main forms:
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Mesh disc type: The most common form, mostly round discs, manually changed, lower cost.
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Mesh belt type: Long strip shape, used for automatic screen changers, allowing continuous or intermittent automatic screen changes, achieving non-stop production and significantly improving efficiency.
Selection key points and combination use
In actual production, filter mesh selection is not a single dimension but a comprehensive consideration of multiple factors. It is usually necessary to combine factors such as raw material characteristics, product quality requirements, equipment configuration, and cost control to determine the most suitable filter mesh type.
In particular, multi-layer combination is a standard practice in the industry. The most common configuration is the “coarse-fine-coarse” structure, for example, 20 mesh / 80 mesh / 20 mesh. The advantage of this structure is that the coarse mesh on both sides provides support and protection, preventing the fine mesh in the middle from being burst by high-pressure melt, thus balancing filtration precision and mechanical strength.