Extruder Operation and Control - Paulson Training

PaulsonTraining
17 Feb 201001:54

Summary

TLDRThis video script explores the inner workings of an extruder, detailing how plastic raw material moves by gravity into the feed throat and is conveyed forward by a rotating screw through a heated barrel. The decreasing channel depth and shear heating from screw rotation melt the plastic. A screen pack and breaker plate filter contaminants, ensuring the melt is well mixed and at the correct temperature and pressure for extrusion.

Takeaways

  • 🔧 The extruder's function is to process plastic raw material into a melt.
  • 📉 The plastic travels by gravity from the hopper to the feed throat.
  • 🔄 The rotating screw conveys the plastic forward through the heated barrel.
  • đŸ”„ Shear heating, caused by compression and screw rotation, melts the plastic.
  • 📍 The channel depth decreases along the screw, forcing the plastic through a smaller area.
  • đŸŒĄïž The barrel heating system works in conjunction with shear heating to melt the plastic.
  • 🔍 A screen pack filters contaminants from the melt.
  • đŸ—ïž The breaker plate supports the screen pack and allows the plastic to pass through.
  • 📉 The screen pack is arranged with the coarsest screen next to the breaker plate for support.
  • ⚙ The screen pack consists of wire mesh filters, typically from 20 to 100 mesh.

Q & A

  • What is the function of the hopper in an extruder?

    -The hopper holds the plastic raw material and allows it to travel by gravity to the feed throat.

  • How does the rotating screw in an extruder contribute to the plastic's movement?

    -The rotating screw conveys the plastic forward through the heated barrel.

  • What is the purpose of the heated barrel in an extruder?

    -The heated barrel helps to melt the plastic as it is conveyed forward by the screw.

  • What is shear heating and how does it occur in an extruder?

    -Shear heating is the generation of heat caused by friction as the plastic is compressed and rotated along the screw.

  • Why does the channel depth decrease along the screw?

    -The channel depth decreases to force the plastic through a smaller area, which helps in melting it by increasing pressure and shear heating.

  • What is the ideal state of the plastic by the time it reaches the end of the screw?

    -By the time the plastic reaches the end of the screw, it should be well mixed, at a proper temperature, and at the necessary pressure for the die.

  • What is the role of the screen pack in an extruder?

    -The screen pack filters contaminants from the melt by forcing the plastic to flow through a set of wire mesh filters.

  • What does the term 'mesh' indicate in the context of screen packs?

    -The term 'mesh' indicates the number of wires per inch in the screen pack filters, typically ranging from 20 to 100 mesh.

  • What is the purpose of the breaker plate in an extruder?

    -The breaker plate is a sturdy metal plate with holes that supports the screen pack and allows the plastic to pass through.

  • Why is the order of screen mesh important in the screen pack?

    -The screen pack must be set with the coarsest screen next to the breaker plate so that each screen can support a finer one, preventing pressure differences from breaking the fine wires.

  • What can happen if the screen pack is not properly set up?

    -If the screen pack is not properly set up, it can contaminate the product, cause damage to the die, and lead to permanent damage.

Outlines

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Mindmap

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Keywords

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Highlights

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Transcripts

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Étiquettes Connexes
Plastic ExtrusionMechanical ProcessShear HeatingThermal MeltIndustrial DesignMaterial HandlingScrew ConveyorFilter SystemContaminant RemovalMelt Mixing
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