Description

The fishbone slot roller shell is a biomimetic design for pellet mill rollers, featuring a surface with herringbone or fishbone-patterned through-groove systems. A central main groove extends along the axial direction, while angled branch grooves on both sides spread outward at symmetrical angles (typically 30°-45°). This structure generates a centripetal converging material pushing force as the roller rotates, moving material from both ends of the roller toward the center, effectively solving the common problems of end material leakage and center material starvation in wide ring dies.

Q: What is the essential difference in material conveying logic between a fishbone slot roller shell and a through oblique slot roller shell?
A: A through oblique slot roller shell generates unidirectional axial thrust, causing material to migrate toward one end. In contrast, the left-right symmetrical branch grooves of a fishbone slot roller shell produce bidirectional centripetal thrust, moving material from both ends toward the center, creating a “self-centering” effect. This makes the fishbone slot roller shell particularly suitable for ultra-wide pellet mills with ring die widths exceeding 400mm, where unidirectional oblique slots would cause severe axial density segregation.

Q: Is there a stress risk at the intersection of the central main groove and branch grooves in a fishbone slot design? How can it be optimized?
A: Yes, the intersection point is a geometric discontinuity zone prone to fatigue crack initiation. Optimization measures include: using large arc transitions (R ≥ 3mm) instead of sharp right-angle intersections; designing gradual groove depth variations (shallower at intersections, deeper at ends); selecting ultra-high toughness alloy steel (e.g., 18CrNiMo7-6) combined with cryogenic treatment. Additionally, shot peening at the intersection points to introduce compressive residual stress layers is recommended.

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