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Everything You Need To Know About Kneader Extruder

In industrial manufacturing, achieving a homogeneous and consistent mixture of high-viscosity materials is crucial. A kneader extruder is a sophisticated piece of equipment designed to meet this challenge. By combining the functions of a kneader and an extruder, this machine ensures efficient mixing, kneading, and shaping of various materials. This article aims to provide a comprehensive understanding of kneader extruders, covering their components, working principles, applications, and benefits.

Components of a Kneader Extruder

A kneader extruder consists of two main sections: the kneader and extruder sections.

The Kneader

The Kneader, many people also call it Banbury mixer or Banbury machine, is a type of internal batch mixer used primarily in the rubber and plastics industries for mixing or compounding materials. It was invented by Fernley H. Banbury in 1916 and has since become a critical piece of equipment in these industries due to its efficiency and effectiveness in mixing high-viscosity materials.

Components of the Kneader

  • Mixing Chamber: The Banbury mixer features a robust, enclosed mixing chamber with a figure-eight shape. This chamber houses two counter-rotating rotors that create intense shearing and mixing actions.
  • Rotors: The rotors in a Banbury mixer are typically of a drilling type, which provides a better cooling effect compared to other types of rotors. These rotors turn towards each other at different speeds, shearing the material between the rotors and the chamber walls.
  • Floating Weight (Ram): A floating weight or ram is used to confine the material within the mixing space and exert additional pressure, enhancing the mixing efficiency.
  • Discharge Mechanism: The mixed material is discharged through a drop door at the bottom of the chamber, which opens to release the compound onto a rolling mill or other processing equipment.

Extruder Section

  • Types of Extruders: The extruder section can be either a single screw or twin screw extruder. Single screw extruders are simpler and often used for basic extrusion tasks, while twin screw extruders provide better mixing and are suitable for more complex materials.
  • Extrusion Die: The die shapes the material as it is pushed through, forming it into the desired shape. The design of the die can be customized depending on the final product requirements.
  • Cooling and Cutting Mechanisms: Once extruded, the material may be cooled and then cut into pellets or other shapes for further processing or packaging.

Types of Kneader Extruders

Kneader+Single Screw Extruders

These machines have a single screw in the extruder section and are typically used for simpler compounding tasks. They are effective for basic mixing and extrusion but may not provide the same level of mixing as twin screw extruders.

kneader compound machine

Working Principle

1. Loading Materials

Raw materials, such as polymers, additives, fillers, and other ingredients, are loaded into the Banbury kneader.

2. Mixing and Kneading

The Banbury kneader, equipped with robust rotors, performs intensive mixing and kneading. The high-shear environment within the kneader ensures that the materials are thoroughly mixed, achieving a homogeneous and consistent blend. The kneading action involves folding, stretching, and compressing the materials under controlled temperature and pressure conditions.

3. Material Transfer

Once the materials are mixed in the Banbury kneader, they are discharged onto a bucket conveyor. This conveyor system transports the mixed materials from the kneader to the next stage of the process.

4. Feeding Mechanism

The bucket conveyor feeds the materials into a conical twin screw force feeder. This feeder ensures a consistent and controlled feed of materials into the single screw extruder.

5. Compacting and Pre-Extrusion

The conical twin screws compact the materials, providing a uniform and steady flow into the single screw extruder. This step helps in maintaining consistent pressure and feed rate, crucial for the efficient operation of the extruder.

6. Primary Extrusion

The compacted material from the twin screw force feeder enters the single screw extruder. The single screw rotates, pushing the material forward through the barrel of the extruder. The design of the screw helps in further mixing and homogenizing the material as it moves along the length of the extruder.

7. Heating and Melting

The material is heated within the extruder barrel, allowing it to melt and become more fluid. The heating elements along the barrel ensure the material reaches the desired temperature for optimal processing.

8. Shaping and Forming

As the material reaches the end of the extruder, it is forced through an extrusion die, shaping it into the desired form. This could be a continuous strand or another predefined shape.

9. Cutting Mechanism

After extrusion, the material can be cut into pellets or other forms using one of two systems:
Air Cooling Hot Face Cutting System: The extruded material is cut at the die face by rotating knives while being cooled by air. This method is suitable for materials that solidify quickly upon cooling.
Water Ring Cutting System: The extruded material is cut by rotating knives and immediately quenched in water, forming pellets. This method is effective for materials that require rapid cooling to solidify.

10. Cooling

The cut material is further cooled to solidify completely. In the air cooling system, ambient air or forced air cools the material. In the water ring system, the pellets are immersed in water for rapid cooling.

11. Storage

The cooled and solidified pellets are then transported to a silo for storage. The silo provides a large capacity for holding the finished product before it is packaged or sent for further processing.

12. Final Processing Steps

From the silo, the pellets can be packaged or transported to subsequent processing stages depending on the production requirements.

Benefits and Applications

Kneader extruders are designed to handle high-viscosity materials effectively, which is essential for masterbatch processing since the polymer and additives require robust mixing to achieve homogeneity when forming highly viscous mixtures.

Kneader extruders would be a nice choice for those manufacturers need to produce different masterbatch formulations. They can process a wide range of polymers and fillers, making them suitable for producing various types of masterbatch, including:

  • Color Masterbatch Compound
  • Carbon Black Masterbatch
  • High Filler Masterbatch:PE/PP+over 85%Caco3
  • EVA Foam Masterbatch
  • Stone Paper Masterbatch
  • Non-woven Masterbatch
  • Woven Bag Masterbatch

In addition, the design of kneader extruders allows for continuous processing, which enhances production efficiency. They can mix, knead, and extrude the material in a single operation, reducing the need for multiple processing steps and thereby increasing throughput.

Kneader+Twin Screw Extruders

Twin screw extruders have two intermeshing screws that provide superior mixing capabilities. They are preferred for complex materials that require thorough mixing and are used in more demanding applications.

Kneader (Banbury) Twin Screw Compound Machine

Working Principle

The working principle of this kneader extruder type is the same as the first kneader extruder (kneader+single screw extruder). Just replace the single screw extruder with twin screw extruder when you process the compacted material from the twin screw force feeder. In the first kneader extruder type, you put this material into single extruder, now you put intto twin screw extruder. The rest works the same as the first knead extruder.

Benefits and Applications

Except its ability to efficiently handle high viscosity materials, when you use twin screw extruder instead of single screw extruder in kneader extruders, it will have more advantages:

  • High shear mixing and homogenization: Ensures uniform dispersion of additives and fillers.
  • Precise temperature and process control: Maintains optimal conditions for sensitive materials and reactions.
  • Enhanced mixing capabilities: Improves mechanical properties and quality of the final product.

This type is also mainly used for masterbatch processing. The specific application area are similar to kneader+single screw extruder.

Kneader (Banbury) Two Stage Extruder

In addition to the previous two extruder types, our company GS mach also has a kneader two stage extruder, which is very popular in places like Turkey. This kneader extruder including three parts: kneader+twin screw extruder+single screw extruder.

Kneader (Banbury) Two Stage Extruder

Working Principle

The beginning part of these three parts are the same, you need to use kneader to process the material first. But when you transfer the material from the kneader, the spiral loader transports the uniformly mixed materials from the high-speed mixer to the twin screw extruder. This system ensures a continuous and consistent flow of material, preventing any interruption in the processing line.

The material will first be processed in twin screw extruder for primary extrusion, enhanced mixing and homogenizing, heating and melting, shaping and forming. An then the partially shaped material from the twin screw extruder enters the single screw extruder. The single screw further processes the material, providing additional mixing, homogenization, and pressure buildup.

The single screw extruder ensures that the material is uniformly and stably extruded through the die at the end of the extruder. This stage finalizes the shape and quality of the extruded material. The rest works the same as the other two knead extruder types.

Benefits and Applications

This kneader extruder not only has the advantages of the other two types, but can also further ensure higher capacity and lower maintenance cost on this basis. Kneader two stage extruders are suitable for following applications:

  • PVC cable compound material
  • Chemical cross-linking cable compound
  • Wood plastic compound
  • High filler masterbatch compound
  • TPE/TPR shoe sole material or filler masterbatch compound

As the first export manufacturer of plastic machinery in China about Two stage/Kneader machine, our strength in producing and developing extruder products is beyond doubt. Welcome to contact us to ask for a quote for the product you want!


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