Screw Root: Root Diameter Range 20-300 mm, Tolerance ±0.05 mm

Component Specifications

Definition

In extrusion machinery, particularly within the compression and transition sections of single or twin-screw extruders, the screw root refers to the cylindrical core of the screw that extends along its axis. This component serves as the structural backbone, providing mechanical strength to withstand torsional and axial loads during polymer processing. It determines the channel depth between flights, directly influencing material compression, shear rates, and residence time distribution. The root diameter typically increases in compression zones to gradually reduce channel volume, facilitating material compaction and pressure buildup essential for homogeneous melt formation.

Working Principle

The screw root operates by rotating within the barrel, transmitting mechanical energy from the drive system to the processed material. As the root diameter varies along the compression/transition section, it reduces the volumetric capacity of screw channels, compressing the material to eliminate air voids, increase density, and generate shear heat through viscous dissipation. This mechanical compression, combined with barrel heating, transitions solid polymer pellets into a uniform molten state suitable for shaping through the die.

Materials

Typically manufactured from high-strength alloy steels (e.g., AISI 4140, H13 tool steel) with surface hardening treatments like nitriding or hard chrome plating to enhance wear resistance. For corrosive applications, stainless steels (e.g., 17-4PH, 316L) or nickel-based alloys may be used.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Tolerance	±0.05 mm
Surface Hardness	50-65 HRC
Root Diameter Range	20-300 mm
Maximum Torque Capacity	Up to 50,000 Nm
Length To Diameter Ratio (L/D)	20:1 to 40:1

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

ISO 12164, DIN 32711

Parent Products

This component is used in the following industrial products

Compression/Transition Section

The section of an extrusion screw where material is compressed and transitions from solid to molten state.

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Engineering Analysis

Risks & Mitigation

Wear from abrasive fillers
Fatigue failure under cyclic loading
Corrosion in aggressive environments
Thermal stress cracking

FMEA Triads

Trigger: Abrasive polymer compounds
Failure: Progressive root diameter reduction
Mitigation: Apply wear-resistant coatings and monitor screw dimensions regularly

Trigger: Excessive torque or misalignment
Failure: Root fracture or twisting
Mitigation: Implement torque monitoring and precision alignment during installation

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Geometric tolerances per ISO 2768-m, surface finish Ra ≤ 0.8 μm

Test Method

Dimensional inspection via CMM, hardness testing per ISO 6508, NDT for cracks per ASTM E1417

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

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Manufacturers of Screw Root

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Frequently Asked Questions

What is the primary function of the screw root in extrusion?

The screw root provides structural integrity to transmit torque while defining channel depth for material compression and melting in the transition zone.

How does root diameter affect extrusion performance?

Increasing root diameter reduces channel volume, enhancing compression ratio and shear rates, which improves melting efficiency but may raise motor load and melt temperature.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification

This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

Screw Root