Reciprocating Screw: Diameter 18-200 mm, L/D Ratio 20:1 to 25:1

Component Specifications

Definition

A reciprocating screw is a precision-engineered rotating and axially moving component within the injection unit of plastic injection molding machines. It performs three primary functions: plasticizing solid polymer pellets through shear heating and barrel conduction, homogenizing the melt through mixing elements, and injecting the molten material into the mold cavity under controlled pressure. The screw rotates to melt material while simultaneously retracting, then moves forward axially (without rotation) to inject the accumulated melt.

Working Principle

The reciprocating screw operates through simultaneous rotation and axial movement. During plasticizing phase, rotation generates shear heat through friction against the barrel wall, melting polymer pellets while retracting to accumulate melt in front. During injection phase, the screw stops rotating and moves forward axially like a plunger, forcing the accumulated molten plastic through the nozzle into the mold cavity under high pressure. This dual-action combines the melting efficiency of a rotating screw with the precise injection control of a plunger.

Materials

Typically manufactured from high-grade alloy steels (AISI 4140, H13 tool steel) with surface hardening treatments (nitriding, chrome plating) for wear resistance. Specialized variants may use bimetallic construction with wear-resistant alloys in high-wear zones.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Diameter	18-200 mm
L/D Ratio	20:1 to 25:1
Flight Depth	Varies along length
Surface Hardness	58-62 HRC
Compression Ratio	2:1 to 3:1
Injection Pressure	100-250 MPa

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 294, DIN 16773

Parent Products

This component is used in the following industrial products

Injection Unit

The component of a silicone molding machine responsible for melting and injecting silicone material into the mold cavity.

View Product Details

Engineering Analysis

Risks & Mitigation

Wear and corrosion reducing efficiency
Material degradation from overheating
Inconsistent melt quality
Mechanical failure under high pressure
Backflow during injection phase

FMEA Triads

Trigger: Abrasive polymer additives
Failure: Excessive screw and barrel wear
Mitigation: Use hardened surfaces, bimetallic barrels, and proper material selection

Trigger: Overheating due to excessive back pressure
Failure: Polymer degradation and black spec formation
Mitigation: Optimize temperature profiles and back pressure settings

Trigger: Improper screw design for material
Failure: Poor melting and mixing quality
Mitigation: Match screw geometry to material characteristics and processing requirements

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

±0.05 mm diameter tolerance, ±0.1 mm straightness over full length

Test Method

Dimensional inspection with micrometers and dial indicators, hardness testing, material composition verification, pressure testing under simulated conditions

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

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Reciprocating Screw

Manufacturer profiles associated with Reciprocating Screw.

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Frequently Asked Questions

What is the difference between reciprocating screw and two-stage screw systems?

Reciprocating screws combine plasticizing and injection in one unit, while two-stage systems separate these functions with a plasticizing screw feeding a separate injection plunger, allowing independent optimization of each function.

How does screw L/D ratio affect injection molding performance?

Higher L/D ratios (typically 20:1 to 25:1) provide longer residence time for better melting and mixing, improved temperature homogeneity, and reduced pressure drop, but require more torque and longer barrels.

What maintenance is required for reciprocating screws?

Regular inspection for wear, cleaning to prevent material degradation, checking for corrosion, monitoring torque requirements, and periodic measurement of critical dimensions to ensure proper clearance with barrel.

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.

Reciprocating Screw