KB Series Kneading Blocks Shear Twin Screw Extruder Parts W6Mo5Cr4V2 6542 HRC 58-HRC 62

KB Series Kneading Blocks & Shear Mixing Elements | Twin Screw Extruder Mixing Segments

KB kneading blocks are core modular mixing shear elements specially designed for intermeshing co-rotating twin screw extruders, matched perfectly with SK series forward/reverse conveying screw elements to form a complete screw layout system. Composed of multiple independent kneading discs arranged at staggered angles, KB blocks provide controllable shear force, strong material folding, stretching and homogenizing capacity, realizing uniform pigment dispersion, filler wetting, polymer melting and reaction compounding.

All KB mixing segments adopt unified standard multi-tooth internal splined bore, fully interchangeable with SK series screw shafts. We provide multiple wear-resistant alloy material solutions with two-stage integral gas nitriding treatment, reaching uniform surface hardness HRC 58–62 for long-cycle continuous compounding production.

According to disc stagger angle, rotation direction and width specification, KB series are divided into 30° low-shear, 45° medium-shear, 60° high-shear three core angle types; each angle supports forward conveying, neutral zero thrust and reverse back-pressure three rotation modes, plus wide/narrow disc width options to freely adjust mixing intensity, residence time and melt pressure.

1. Adjustable shear intensity by disc stagger angle

   30° small angle delivers gentle low shear, avoids polymer degradation for heat-sensitive materials; 45° medium angle balances mixing effect and material residence time for universal masterbatch; 60° large angle generates strong high shear for high-filler, hard agglomerate breaking and full dispersion.

2. Three-way thrust design for flexible pressure control

   Forward KB blocks push melt downstream for smooth conveying after mixing; neutral kneading discs generate no axial thrust, stabilize barrel filling length; reverse KB segments create local back-pressure to extend material residence time and strengthen homogenization.

3. Split multi-disc stacked combination

   Single kneading block consists of 3–5 kneading discs, customers can stack multiple KB blocks in series to customize mixing length without replacing screw shafts.

4. Universal spline interchange system

   Consistent splined hole standard with all SK conveying elements, one screw shaft compatible with full set conveying + mixing segments, reduce spare part inventory cost.

5. High wear & corrosion resistance metallurgy

   Optional W6Mo5Cr4V2 high speed steel, 1.2343 hot work steel, HIP powder alloy and Hastelloy anti-corrosion alloy, meet production demands of glass fiber, talc, carbon black, corrosive additives and food-grade raw materials.

6. Smooth polished disc surface

   Mirror polishing after nitriding eliminates melt stagnation dead zones, prevent carbon deposition and material discoloration during long-time running.

Gentle mixing, minimum shear heat generation.

Application: PLA/PBAT biodegradable plastic, PVC heat-sensitive material, low-melt-strength polymer, color masterbatch with fine pigment, food & medical grade extrusion.

Balanced dispersion & distribution mixing, most universal model.

Application: General PP/PE color masterbatch, glass fiber reinforced PA/PC, mineral filled plastic, recycled plastic granulation, standard compounding production lines.

Powerful cutting & breaking capacity, strong agglomerate dispersion.

Application: High-concentration carbon black masterbatch, high talc/calcium carbonate filling, carbon fiber composite, hard additive agglomerate dispersion, reactive extrusion.

1. Forward KB Kneading Block: Axial forward conveying force, melt flows smoothly to next barrel zone, used in main mixing zone without pressure accumulation.
2. Neutral KB Kneading Block: No axial push/pull force, lock material residence time, stabilize barrel filling length, matched before vacuum vent section.
3. Reverse KB Kneading Block: Backward thrust to build local melt back-pressure, extend mixing time, installed after main mixing zone for deep homogenization.

• Wide kneading disc: Longer material contact time, strong distribution mixing, for uniform blending of multiple components.
• Narrow kneading disc: Short residence time, concentrated shear force, focused dispersion for hard agglomerates.

Standard Process: Two-stage gas nitriding + precision mirror polishing

Complete extrusion screw zone order:

1. Feed section: SK96/96 + SK96/48 large pitch conveying elements
2. Melting pre-transport: SK72/72 medium pitch conveying blocks
3. Main mixing zone: Stacked KB kneading blocks (match shear angle based on raw material)
4. Mixing post buffer: SK64/64 medium-small pitch conveying
5. Vacuum vent front sealing: SK64/32 short conveying + SK reverse sealing R series
6. Metering & die front: SK48/SK36/SK24 small pitch conveying elements

Matching Tips:

• Heat-sensitive material: Adopt 30° forward KB blocks, reduce stacked quantity, add neutral KB before vent to avoid over-shear.
• High-filler masterbatch: Use 60° high shear KB groups, match reverse KB to extend mixing residence time.
• Vacuum degassing formula: Place neutral KB after mixing zone to stabilize melt filling ratio, prevent vent surging.