Choosing the right screw barrel for plastic extrusion has a direct impact on output, plasticizing quality, energy consumption, and service life.

Many buyers focus only on screw diameter when ordering a replacement screw and barrel. However, diameter is only one part of the specification.

At Juyuan, we manufacture screw barrels for different extrusion applications. Based on our experience, the following factors should be checked before manufacturing a replacement set.

1. Confirm the Screw Diameter and L/D Ratio

The first step is to confirm the screw diameter.

Common extrusion screw diameters include:

• 45 mm
• 55 mm
• 65 mm
• 75 mm
• 90 mm
• 120 mm
• 150 mm
• 180 mm

The L/D ratio is also important.

For example, a 90 mm screw with an L/D ratio of 30:1 has a different working length from a 90 mm screw with an L/D ratio of 25:1.

Never order a replacement screw based only on diameter.

2. Tell the Manufacturer What Material You Process

Different plastics require different screw designs.

Typical materials include:

• HDPE
• LDPE
• PP
• PVC
• ABS
• PC
• PET
• PA
• Recycled plastics

The screw compression ratio, flight depth and mixing section should be designed according to the material.

For recycled plastics or materials containing fillers such as calcium carbonate or glass fiber, wear resistance becomes especially important.

3. Choose the Correct Screw Barrel Material

Material selection affects the lifetime of the screw and barrel.

A common option is 38CrMoAlA nitrided steel. After nitriding treatment, the surface obtains good hardness and wear resistance and is suitable for many standard extrusion applications.

For more abrasive materials, a bimetallic screw barrel is often a better choice.

A bimetallic barrel has a wear-resistant alloy layer on its inner surface, while the screw can also receive alloy treatment on the flight surface.

This can significantly improve service life when processing recycled or highly filled plastics.

4. Check the Existing Screw for Wear

Before replacing the screw barrel, inspect the old components.

Common signs of wear include:

• Reduced extrusion output
• Unstable pressure
• Poor plasticizing
• Higher melt temperature
• Increased motor load
• Excessive clearance between screw and barrel

When the clearance becomes too large, molten plastic can flow backward over the screw flights.

This reduces conveying efficiency and production output.

5. Provide Drawings or Measurements

The safest way to manufacture a replacement screw barrel for plastic extrusion is to provide the original technical drawing.

If no drawing is available, accurate measurements are required.

Important dimensions normally include screw diameter, total length, working length, connection dimensions, keyway dimensions, barrel outside diameter, flange dimensions and heater positions.

Photos of the existing screw and barrel are also helpful.

For complicated components, sending the old sample to the manufacturer for measurement can reduce the risk of dimensional errors.

6. Consider Your Required Output

Output requirements should also be discussed before manufacturing.

For example, two extrusion lines may both use a 90 mm screw but have different production targets.

The screw geometry can be optimized according to:

• Material
• Required kg/h
• Screw speed
• Motor power
• Die resistance
• Extrusion pressure

A properly designed screw can improve output without simply increasing screw speed.

7. Do Not Choose Only by Price

A low-priced screw barrel may reduce the initial purchasing cost, but premature wear can result in much higher production losses.

The real cost includes downtime, reduced output, energy consumption, maintenance and replacement frequency.

For continuous production lines, service life and stable performance are often more important than the lowest purchase price.

Conclusion

Choosing the correct screw barrel for plastic extrusion requires more than confirming the screw diameter.

The manufacturer should understand your machine specifications, processed material, production capacity and wear conditions before recommending the screw design and material.

If you need a replacement screw and barrel, send us your machine model, screw diameter, drawings or photos, processed material and required output.

Juyuan can manufacture customized screw barrels for extrusion and injection molding machines according to your actual production requirements.