Many customers mistake the serrated openings on the outer edge of spiral blades for processing defects, but this is actually a targeted structural design rather than a defective product. The serrated openings are mostly applied to single-piece welded spiral blades and can be used on partial shaftless and shafted screw conveyors. Designed for complex material working conditions, they solve conveying problems that cannot be addressed by ordinary solid blades.
I. Four Core Functions of Serrated Outer Edge Blades
1. Cutting Fibrous Materials to Prevent Winding and Agglomeration
When ordinary integral blades convey long-fiber materials such as cloth strips, crop straw, hemp ropes, chemical fibers and domestic waste, the fibers tend to continuously wind around the outer edge of the blades and accumulate layer by layer, leading to increased load and material blockage shutdowns.
The serrated outer edge forms a circle of cutting edges. When materials pass through, the serrations can cut off long fibers, avoiding fiber winding between blades and cylinder walls and reducing the probability of machine jamming.
2. Breaking Caking Materials to Disperse Material Masses
Moist caked powder, pasty agglomerates and wet mineral materials easily form solid masses when entering the conveyor. These masses are pushed forward integrally, which reduces conveying efficiency and causes partial overload.
The serrated edges can cut and pound caked materials, breaking large material masses into loose materials. This improves material fluidity and ensures smoother conveying.
3. Scraping Adherent Materials off Cylinder Walls to Reduce Wall Deposition
Wet and viscous materials easily adhere to the inner wall of the conveyor shell. Over time, thick material layers form on the inner wall, narrowing the effective conveying space and continuously lowering the conveying capacity.
The serrated outer edge fits closely to the inner wall of the cylinder. As the blade rotates, the serrations can scrape off adherent materials on the cylinder wall, achieving a simple self-cleaning effect, reducing material accumulation and lowering maintenance frequency.
Note: Serrated blades cannot fully replace professional wall-cleaning scrapers. Rubber cleaning plates are still required for working conditions with severe material adhesion.
4. Reducing Friction Resistance Between Blades and Shell
For integral round blades with a small gap between the outer edge and the cylinder wall, hard particles mixed in materials will cause direct friction between the blade outer edge and the shell, resulting in loud noise and rapid wear.
The open serrated structure reduces the contact area between the blade outer edge and the cylinder wall. Hard particles can escape through the serration gaps, preventing hard materials from jamming between the blade outer edge and the machine shell, lowering friction and wear, and mitigating the risk of overload seizure.
II. Applicable Working Conditions for Serrated Blades
✅ Applicable Scenarios
1. Conveyance of materials containing cloth strips, crop straw and fibrous impurities
2. Easily damp-caked powder materials, mineral residues and leftover materials
3. Highly viscous materials prone to adhering to and depositing on shell walls
❌ Non-recommended Scenarios
1. Fine dry powder and grain particles: Fine materials are likely to be trapped in serration gaps and form residual deposits, causing inconvenient cleaning and sanitation problems.
2. Highly abrasive sand and gravel working conditions: Serrated tips are weak points and wear rapidly, losing their functions once worn flat.
3. Sanitation-critical food and pharmaceutical working conditions: Gaps tend to trap materials and breed impurities. Smooth solid blades are preferred for such scenarios.
III. Common Selection Misconceptions
1. More serrations do not mean better performance: Excessively large serration openings reduce the strength of blade outer edges and may cause serration tip fracture under heavy loads; excessively small serrations weaken the cutting and dispersing effect. The height and spacing of serrations need to be customized according to material characteristics.
2. Serrated blades cannot increase conveying capacity: They are mainly designed to solve problems of material winding, caking and wall adhesion, rather than improve conveying efficiency. Solid blades deliver higher conveying performance for pure granular materials.
3. Serrated tips are vulnerable wearing parts: Long-term conveyance of hard materials will gradually blunt the serrated tips and eliminate their cutting function. Blades need to be replaced once severely worn.
IV. Selection Summary
The serrated outer opening is a functionally improved structure, featuring cutting fibers, breaking caked materials and scraping adherent materials off cylinder walls.
Ordinary solid single-piece spiral blades are suitable for clean and loose granular materials.
Serrated outer edge blades are recommended for materials with abundant impurities, fibers, or prone to caking and wall adhesion, which can effectively reduce conveyor faults such as material blockage and winding.
When purchasing and customizing spiral blades, inform the manufacturer of actual material conditions to confirm the necessity of serrated outer edges and avoid blind selection.
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