Extrusion Screw for Food Extruders

Product Specifications

Technical details and manufacturing context for Extrusion Screw

Definition

The Extrusion Screw is a critical rotating component within an industrial food extrusion and forming machine. It is typically a long, helically-flighted shaft housed inside a stationary barrel. Its primary function is to transport raw food ingredients, such as dough or cereal mix, from the feed hopper, apply mechanical shear and compression to plasticize and cook the material, and finally force the homogeneous melt through a die to form the final product shape. The screw's geometry, including pitch and channel depth, is designed to progressively compress, shear, and heat the material through mechanical energy and often external barrel heating, transforming it into a viscous, homogeneous plastic mass before extrusion. The screw operates within a specified range of parameters: screw diameter from 20 to 200 mm, length-to-diameter ratio (L/D) from 20 to 40, screw speed from 30 to 300 rpm, throughput capacity from 50 to 2000 kg/h, operating temperature from 100 to 250 °C, and operating pressure from 1.0 to 1.6 MPa. Materials on file include nitrided steel (e.g., 38CrMoAlA per GB/T 3077) and bimetallic alloys with a steel base and hard-facing alloy. Surface hardness ranges from 60 to 65 HRC, surface roughness from Ra 0.4 to 0.8 µm, and screw weight from 10 to 500 kg. These values are directory reference ranges and must be verified for the specific model and application. The screw is a wear-prone component; regular inspection for wear, corrosion, and dimensional changes is essential. When selecting or replacing a screw, verify the exact dimensions, material grade, and surface treatment with the legal manufacturer or supplier. Always confirm that the screw meets the required standards and is compatible with the extruder's design and food safety requirements.

Working Principle

The screw rotates within a stationary barrel. Raw material is fed into the flights. As the screw turns, the material is conveyed forward. The geometry of the screw (pitch, channel depth) is designed to progressively compress, shear, and heat the material through mechanical energy (and often external barrel heating), transforming it into a viscous, homogeneous plastic mass before it is extruded through the die. The screw's speed and design determine the shear rate and residence time, affecting the final product quality.

Common Materials

Nitrided Steel, Bimetallic Alloy (e.g., steel base with hard-facing alloy)

Technical Parameters

Parameter	Typical range	Notes & selection driver
Screw Diameter	20–200 mm	Determines throughput and machine size.
Length-to-Diameter Ratio (L/D)	20–40	Higher L/D improves mixing and melting.
Screw Speed	30–300 rpm	Affects shear rate and residence time.
Throughput Capacity	50–2000 kg/h	Matches extruder size and product demand.
Operating Temperature	100–250 °C	Typical range for food extrusion.
Screw Material	38CrMoAlA	Nitrided steel for wear resistance.GB/T 3077
Surface Hardness	60–65 HRC	Nitriding depth 0.4–0.6 mm.
Surface Roughness	Ra 0.4–0.8 µm	Smooth finish reduces food adhesion.
Screw Weight	10–500 kg	Depends on diameter and length.

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

Components / BOM

Feed Section Part
Conveys solid feedstock from the hopper into the barrel and begins compaction.

Material: Steel
Compression/Transition Section
Gradually reduces channel depth to compress, shear, and melt the material.

Material: Hardened Steel Alloy
Metering Section
Provides final homogenization and steady pressure to pump the melt towards the die.

Material: Hardened Steel Alloy
Flight Part
The helical ridge that conveys and shears the material.

Material: Wear-Resistant Alloy

Manufacturers of Extrusion Screw

Manufacturer profiles associated with Extrusion Screw.

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Frequently Asked Questions

What are the typical materials used for food extrusion screws?

Common materials include nitrided steel (e.g., 38CrMoAlA per GB/T 3077) and bimetallic alloys with a steel base and hard-facing alloy. The choice depends on the application and required wear resistance.

How do I determine the correct screw diameter and L/D ratio for my extruder?

The screw diameter and L/D ratio must match the extruder's barrel and processing requirements. Directory reference ranges are 20–200 mm for diameter and 20–40 for L/D. Always consult the extruder manufacturer or a qualified engineer for exact specifications.

What maintenance is required for an extrusion screw?

Regular inspection for wear, corrosion, and dimensional changes is essential. Check surface hardness and roughness periodically. Replace the screw when wear affects performance or product quality.

Can the operating pressure range be used for all food extrusion applications?

No, the pressure range of 1.0–1.6 MPa is a typical reference. Actual operating pressure depends on the material, screw design, and process conditions. Verify with the manufacturer for your specific application.

Data Basis

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Preliminary Technical Classification

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pressure:	Up to 100 MPa (1000 bar) maximum
flow rate:	0.1-10,000 kg/h (varies by screw diameter and speed)
temperature:	50-300°C (depending on material and screw design)
slurry concentration:	Up to 80% solids by weight (for food-grade applications)

Extrusion Screw

Product Specifications

Industrial Ecosystem & Supply Chain Structure

Application Fit & Sizing Matrix

Reliability & Engineering Risk Analysis

Compliance & Manufacturing Standards