Air Jet Loom

The process where the weft yarn is passed through the shed using air is called air jet weaving. In an air jet loom, the weft insertion is achieved by propelling the weft yarn through the shed with the help of a high-velocity air stream.

Features of Air Jet Weaving Machine:

  1. High Weft Insertion Performance:
    • Air jet weaving machines excel in weft insertion performance.
  2. Productivity for Light to Medium Weight Fabrics:
    • Most productive for manufacturing light to medium-weight fabrics.
    • Ideal for cotton and certain man-made fibers (sheets, shirting fabrics, linings, taffetas, and satins in staple yarns of man-made fibers).
  3. Versatility in Fabric Production:
    • Positive results with heavy-weight fabrics like denims.
    • Some models cater to terry production.
  4. Customization and Bulk Production:
    • Ideal for bulk production of customized fabric styles.
  5. Weaving Widths:
    • Weaving widths generally range from 190 to 400 cm.
  6. Multicolor Weft Carrier:
    • Supports up to 8 different wefts for multicolor fabric production.
  7. Energy Consumption:
    • Requires high energy consumption for compressed air preparation.
    • Consumption increases with wider loom width and higher running speed.
  8. Robust Frame Structure:
    • Features a robust frame structure for durability.
  9. Essential Productivity Factors:
    • Smooth warp shed for efficient operation.
    • Well-balanced beating system.
    • Best weft insertion system.
  10. Low Vibrations:
    • Minimizes vibrations during operation.
  11. Free Drum Pooling System:
    • Equipped with a free drum pooling system in the yarn-advancing reel as standard.
    • Stabilizes insertion with reduced yarn breakage, especially at high-speed or extra-wide weaving.
  12. Computerized Controlling System:
    • Utilizes a computerized controlling system for easy operation and supervision.

Working Principle:

  1. Yarn Package (Cone): The journey begins with the yarn wound on a cone package, providing a convenient way to store and transport the yarn.
  2. Tension Device: As the yarn unwinds from the cone, it passes through a tension device crucial for maintaining consistent tension, ensuring yarn stability.
  3. Accumulator: The yarn progresses to the accumulator, storing a length to manage yarn supply and regulate flow effectively.
  4. Balloon Breaker: Continuing its path, the yarn encounters the balloon breaker, preventing balloon formation during insertion and ensuring a smooth process.
  5. Weft Break Sensor: Next, the yarn passes through the weft break sensor, designed to grip and halt the machine if the weft yarn breaks, preventing issues.
  6. Fixed Main Nozzle: After the weft break sensor, the yarn advances to the fixed main nozzle, a key component in the weft insertion process.
  7. Movable Nozzle: Subsequently, the yarn moves to the movable nozzle, a dynamic component contributing to the precise insertion of the weft.
  8. Shed with Profile Reed: The yarn then passes through the shed, utilizing a profile reed to control airflow according to velocity, enhancing the weaving process.
  9. Relay Nozzle: Following the shed, relay nozzles release air sequentially, contributing to the controlled insertion of the weft and ensuring uniformity.
  10. Cutter: A cutter comes into play, cutting the yarn after proper insertion.
  11. Waste Cutter and Suction Nozzle: Finally, a waste cutter trims any extra yarn, and a suction nozzle is employed to remove waste yarn, maintaining a clean process.
Sketch

Quality of compressed air:

1. Moisture: a. Complete Removal of Liquid: Ensure that any liquid is entirely removed from the compressed air. b. Moisture Removal: It’s essential to eliminate moisture from the air. The dew point of the compressed air should be 10°C or lower. The recommended dew point is between 4°C to 10°C. c. Consequences of Moisture Retention: – Corrosion of metallic components in equipment and piping. – Adhesion of impurities such as dust in the compressed air pipe. – Increased passage resistance and pressure loss, resulting in pinholes in the pipe wall and air leakage. – Reed soiling, leading to inefficient weft insertion and fabric quality impairment.

2. Grease: a. Removal of Oil Aerosol and Larger Grease Particles: Ensure the removal of oil aerosol (0.8 to 0.01 micron particles) and larger grease particles. b. Consequences of Incomplete Removal: – Corrosion of metallic parts in equipment and piping. – Adherence of foreign particles to the pipe. – Soiling of woven cloth. – Reed soiling and inefficient weft insertion. Certain types of grease may damage the reed. – Unhygienic operational environment.

3. Foreign Particles and Carbon:
a. Removal of 0.3 Micron or Larger Particles and Carbon: Remove particles with a size of 0.3 microns or larger, as well as carbon.
b. Consequences of Retaining Particles and Carbon: – Reduction in nozzle efficiency. – Compromised valve operation security. – Soiling of the reed due to particles mixed with grease and moisture. – Equipment malfunction caused by the presence of foreign particles and carbon.

Air Preparation for Air Jet Weaving:

  1. Receive:
    • Natural air is received in this section.
  2. Filtration:
    • Filtration removes dust particles and large foreign matter from the air.
  3. Compressed Air:
    • The air is compressed to a pressure of 6 bars.
  4. Drying:
    • Moisture in the air is removed in the drying section.
    • Cooling is done, and water and oil particles are condensed.
  5. Separation:
    • Separation of condensed water and oil particles occurs in this section.
  6. Micro Filtration:
    • Very fine water, oil, and dust particles are removed through microfiltration.
  7. Reserve:
    • The clean and saturated compressed air is reserved in a reservoir.
    • The air pressure in the reservoir is maintained at 8 to 10 bars.

Attempts to control uniform air jet pressure in air jet weaving involve several strategies:

  1. Auxiliary Jet:
    • Importance: The pressure in the jet is crucial for accurate picking.
    • Approach: An auxiliary jet is employed along with the main jet to maintain uniform pressure.
    • Adjustment with Loom Width: The number of auxiliary jets per unit length increases with the width of the loom.
  2. Special Construction of Jet Path:
    • Structural Enhancement: Two metal plates are positioned both upward and downward of the warp line, forming a horizontal placement.
    • Triangular Flow Path: The design creates a wider flow path in the jet’s feed position, forming a triangular passage.
    • Deflection Control: Deflection within the triangular passage helps in regulating the air pressure.
    • Thin Metal Plates: Some looms use a series of thin metal plates at regular intervals, placed at right angles with the weft line.
    • Triangular Passage: The plates have holes, wider and gradually lower at the ejecting side, forming a triangular passage. This structure controls the air jet, and a slit in the plate releases the weft during beat-up.
  3. Hollow Rapier Insertion:
    • Configuration: Two hollow rapiers are inserted on each side of the loom.
    • Air Jet Passage: The air jet passes through this hollow tube.
    • Weft Control: Weft yarn passes uniformly with this jet, ensuring regular control of the air jet.
  4. Relay Nozzle/Supplementary System:
    • Advanced System: The relay nozzle system is a modern and active approach.
    • Nozzle Placement: Relay nozzles are strategically placed at regular intervals on the sley.
    • Weft Transportation: The jet from relay nozzles carries the weft from one side to another, contributing to regular and controlled air jet action.
  5. Profile Reed:
    • Component Addition: A suction pipe is incorporated at the off end of the loom.

Defects in air-jet weaving:

  1. Pile-Up and Buckle Tip of Yarn:
    • Cause: Defects may occur due to air resistance, leading to the piling up and buckling of the yarn.
  2. Loop Formation Along Weft Direction:
    • Cause: Variations in air pressure can result in the formation of loops in the weft yarn along the weft direction.
  3. Snarl Formation:
    • Cause: Excessive main nozzle pressure combined with low filling tension can lead to snarl formation, which is considered a fabric fault.
  4. Miss Pick or Broken Pick:
    • Cause: Excessive air pressure from the main nozzle can cause misses or breaks in the insertion of the pick.
  5. Filling Stop:
    • Cause: Variations in air pressure can lead to filling stops, representing a defect in the weaving process.
  6. Double Pick:
    • Cause: Improper setting of air pressure may result in double picks, where two picks are inserted instead of one. This is a defect in air jet weaving.
  7. Untwisting of Weft:
    • Cause: The air jet weaving process may lead to the untwisting of the weft yarn, impacting the overall quality.
  8. Buckling or Cockling:
    • Cause: Buckling or cockling may occur as a result of variations or inconsistencies in the air jet weaving process.

Advantages of Air-Jet Loom:

  1. High Productivity:
    • Air-jet looms exhibit high productivity, contributing to efficient weaving processes.
  2. Low Initial Outlay:
    • The initial investment required for air-jet looms is relatively low compared to other types of looms.
  3. High Filling Insertion Rates:
    • Air-jet looms can achieve high rates of filling insertion, enhancing efficiency in fabric production.
  4. Weft Insertion Performance:
    • The weft insertion performance is notably high, typically reaching speeds of 600 picks per minute (pm).
  5. Simple Operation and Reduced Hazard:
    • Air-jet looms feature simple operation with few moving parts, reducing operational hazards.
  6. Reduced Space Requirements:
    • These looms have compact designs, requiring less floor space in the weaving facility.
  7. Standard Width:
    • The standard width of air-jet looms is typically 190cm, providing versatility in fabric production.
  8. Low Noise and Vibration Levels:
    • Air-jet looms operate with low noise and vibration levels, contributing to a quieter and smoother working environment.
  9. Low Spare Parts Requirement:
    • The maintenance of air-jet looms is facilitated by a low requirement for spare parts.
  10. Low Power Consumption:
    • Air-jet looms consume minimal power, contributing to energy efficiency.
  11. Reliability and Minimum Maintenance:
    • These looms are known for their reliability, requiring minimal maintenance efforts.

Disadvantages of Air-Jet Loom:

  1. Broken or Miss Pick:
    • Excess air pressure from the main nozzle can lead to broken or miss picks in the weaving process.
  2. Pile Up and Buckle Tip of Yarn:
    • Air resistance in air-jet looms may result in the formation of pile up and buckle tips in the yarn.
  3. Double Pick:
    • Air-jet looms may experience issues like double picks, impacting the quality of woven fabric.
  4. Loop Formation Along Weft Direction:
    • Variations in air pressure can lead to the formation of loops in the weft yarn along its direction.

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