SK 72/72 SK 72/36 Forward Conveying Elements Medium Pitch Twin Screw Transition Blocks

SK 72/72 SK 72/36 Forward Conveying Elements | Medium Pitch Twin Screw Transition Blocks

Compact half-length SK72 screw segment

General Overview

SK 72/72 and SK 72/36 are medium 72mm pitch single-flight SK series forward conveying elements, specially engineered for the middle melting & transition barrel zones of Ky co-rotating twin screw extruders, serving as the critical transition link between large-pitch SK96 feed throat blocks and small-pitch 56/44 melting segments.

Both adopt unified standard multi-tooth internal splined bore, fully interchangeable with matching SK series core shafts, and support W6Mo5Cr4V2 high-speed steel, 1.2343 hot work steel and HIP powder alloy with integral gas nitriding (HRC58–62 wear resistance).

The defining functional gap lies in axial length and spiral loop structure, which separates their production positioning completely:

• SK 72/72: 72mm full axial length = one complete 360° spiral loop, designed for continuous, uniform medium-volume melt transportation in main mid-melting zones.
• SK 72/36: 36mm half axial length = half spiral flight, stackable modular short segment for staged mild pressure build-up and narrow barrel buffer conveying.

Unlike large-pitch SK96 series blocks that only fit raw material feed throat, all pitch-72 SK segments focus on downstream melting, mixing transition and pre-devolatilization zones.

SK 72/72 Forward Conveying Element: Full-Loop Continuous Mid-Zone Transport Block

Unique Structural Features

72mm pitch paired with matching 72mm full axial length forms an intact single spiral channel, one full rotation delivers a complete cycle of material axial movement. The widened flat pushing flight maintains stable medium free volume, without the over-large throughput of SK96 series, and avoids the flow fluctuation of segmented short blocks. Single-piece integrated structure eliminates assembly gaps inside the melting barrel.

Exclusive Performance Advantages

1. Stable uniform medium flow: Balanced conveying capacity between high-throughput SK96 feed blocks and low-flow small-pitch melting segments, eliminates sudden flow surges/drops during material phase change from solid to melt.
2. Continuous wipe-free melt transport: Smooth full spiral flight reduces local melt stagnation, lowers carbon deposition risk for long-running engineering plastic production.
3. Simplified mid-barrel layout: Single-piece installation meets standard melting zone length requirements, reduces screw stacking joints that cause material dead zones.
4. Mild baseline pressure generation: Moderate channel compression builds steady low baseline melt pressure, ideal for uniform mixing before KB kneading blocks.

Exclusive Applicable Barrel Zones & Materials

Core working zones: Main mid-melting barrel, post-feed transition section, stable transfer channel before kneading mixing blocks.

Target materials: General PP/PE color masterbatch, unfilled engineering plastic blends, medium-density pellet compounding, non-heat-sensitive universal polymer formulations.

Not suitable: Narrow short barrel gaps, low-density fine powder, vacuum vent front buffer conveying (choose SK72/36 instead).

SK 72/36 Forward Conveying Element: Compact Stackable Modular Gradient Transition Segment

Unique Structural Features

Same 72mm medium spiral pitch as SK72/72, but only 36mm half axial length, carrying half spiral flight per unit. Modular split design allows customers to stack 2–4 pieces freely to customize total conveying length, adapting to shortened modified barrel sections that cannot fit full-length SK72/72 blocks. Miniaturized body fits narrow intermediate barrel gaps between mixing and vent zones.

Exclusive Performance Advantages

1. Multi-stage gradual pressure gradient: Stacked multiple SK72/36 segments create incremental mild compression, prevents sharp pressure spikes that trigger foaming for heat-sensitive filled polymers.
2. Adjustable limited instantaneous flow: Single half-length flight restricts melt throughput, stabilizes flow for low bulk-density powder additives and lightweight fillers prone to overflow.
3. Multi-position compatibility beyond main melting zone: Breaks the single melting zone limitation of SK72/72, works for pre-vacuum vent buffer, side-feeder transfer channel, post-kneading pressure relief section.
4. Fine-tunable residence time: Separate short segments control local melt staying duration, avoid over-shearing degradable biopolymers.

Exclusive Applicable Barrel Zones & Materials

Core working zones: Short modified transition barrels, pre-devolatilization vent front buffer zone, side feeder auxiliary transfer channel, post-kneading pressure stabilization section.

Target materials: Glass fiber filled PA/PC, low-density talc/carbon black powder masterbatch, PLA/PBAT biodegradable plastics, recycled fine powder compounding, high-sensitivity low-shear formulations.

Not suitable: Standard full-length main melting zones requiring continuous long-distance melt transport (choose SK72/72).

Comparative Technical Specification Table

Professional Screw Combination Matching Guide

1. Standard Complete Production Layout (Universal Masterbatch): 1~2 pcs SK96/96 (main feed throat) + 2~3 pcs SK72/72 (mid-melting continuous transport) + KB kneading blocks
2. Modified Shortened Barrel Layout (Compact Extruder): Cancel long SK72/72, adopt stacked SK72/36 multi-segment combination for narrow transition zones
3. Heat-Sensitive Filled Bioplastic Layout: SK96/48 feed transition + stacked SK72/36 gradient compression, no full-length SK72/72 to avoid over-pressure
4. Devolatilization Compounding Layout: Install 2~3 SK72/36 before vacuum vent ports for stable flow buffering; SK72/72 only used far upstream melting zone
5. Stepwise Gradient Screw Transition Standard: SK96 (large pitch feed) → SK72 series (medium pitch melt transport) → SK56/SK44 (small pitch metering)

FAQ

Q1: What is the core difference between SK 72/72 and SK 72/36 conveying elements?

A1: Both share the same 72mm medium spiral pitch for mid-extruder zones, the key distinction is axial length and spiral loop structure. SK72/72 is a full 72mm single-loop integrated block for continuous stable melt transport in standard melting barrels. SK72/36 is half-length 36mm modular short segment, stackable for staged gradual pressure adjustment and narrow barrel buffer conveying, cannot replace SK72/72 for long-distance continuous melt transfer.

Q2: When to select SK 72/72 instead of SK 72/36?

A2: Choose SK72/72 if your extruder has standard full-length mid-melting barrel sections; you produce non-sensitive general-purpose plastic masterbatch requiring long continuous uniform melt transportation; you want to reduce screw stacking joints inside the melting zone.

Q3: When should I use SK 72/36 instead of SK 72/72?

A3: Pick SK72/36 when you have modified short narrow barrel transition gaps; process heat-sensitive, low-density fine filler materials prone to foaming/overflow; need flow buffer conveying before vacuum devolatilization vents; require flexible adjustable total conveying length via modular stacking.

Q4: Can two SK 72/36 segments replace one SK 72/72 element?

A4: Two stacked SK72/36 reach total 72mm length matching SK72/72 dimension, but conveying performance differs greatly. Stacked SK72/36 deliver segmented slow gradient flow with mild multi-stage pressure, while single SK72/72 provides one-piece smooth continuous medium melt throughput. They cannot fully substitute each other for strict uniform melting formulations.

Q5: How do SK72 series elements differ from SK96 pitch-96 conveying blocks?

A5: SK96 large 96mm pitch blocks are exclusively designed for raw solid material feed throat with maximum high throughput. SK72 medium 72mm pitch segments are applied downstream in melting, transition and vent zones for molten plastic transport, with balanced moderate conveying capacity to stabilize solid-to-melt phase transition.

Q6: What is the production lead time for pitch72 SK conveying elements?

A6: Standard W6Mo5Cr4V2 SK72/72 & SK72/36 are in stock for shipment within 3–5 working days. Custom alloy material, special flight chamfer or exclusive spline tooth size orders take 15–25 working days; bulk wholesale orders enjoy tiered volume discounts, free laser engraving of customer part numbers.

CTA

Provide your extruder barrel layout, polymer formulation filler type and target screw assembly scheme for our engineering team. We offer free mid-stage gradient screw stacking design solutions for SK 72/72 continuous transport blocks and SK 72/36 modular transition segments, supply lab test samples and factory-direct bulk pricing for twin screw extruder spare parts. Contact us via WhatsApp or email for complete technical dimension drawings.

Factory View