yarn manufacturing (yarn faults)

Submitted by: Asif Ahmed TonmoyID: 131-23-3505 ; Sec: D(L 3T1)

Assignment topic: Different kinds of yarn faults.

Submitted to: Lecturer

Daffodil International University

Nadim Haider Maruf

Yarn faults

The defects of yarn is called Yarn faults.When an uneven place or impurities or any

other lack of minimum quality is found in a yarn is called yarn defects or faults.

Yarn content in the cop is less

EFFECTEfficiency loss in ring frame

•Drop in winding efficiency •More knots for a given length of wound yarn

CAUSESUnder utilization of bobbin height

Lower number of coils /inch Higher chase length Cop bottom bracket properly not set Improper selection of ratchet Ratchet pawl pushing number of teeth's /movement in the ratchet wheel Spinning empties wall thickness is high

RECTIFICATIONOptimum chase length, coil spacing and wall thickness of empty cops tobe ensured

1. Ratchet/pawl movement to be properly set 2. Free space of only 7.5mm to be maintained at the top and bottom of the

cop 3. Free space only 0.75mm only to be maintained between full cops and the

ring

An abnormally thick place or lump in yarn showing less twist at that

place.

EFFECTMore end breaks in the next process.

Damaged fabric appearance. Shade variation in dyed fabrics.

CAUSES

Accumulation of fly and fluff on the machine parts. Poor carding. Defective ring frame drafting and bad piecing Improperly clothed top roller clearers.

RECTIFICATION1. Machine surfaces to be maintained clean. 2. Proper functioning of pnemafil /roller clearers to be ensured. 3. Broken teeth gear wheel to be avoided and proper meshing to be

ensured. 4. Better fiber individualization at cards to be achieved. 5. Optimum top roller pressure &back zone 6. Setting at ring frame to be maintained.

Yarn containing rolled fibre mass, which can be clearly seen onblack board at close distance; measurable on Usterimperfection Indicator.

EFFECTDamaged fabric appearance

•Shade variation in the dyed fabrics •An abnormally thick place or lump in yarn showing less twist at that place is called slubs

CAUSESAccumulation of fly and fluff on the machine parts

Poor carding. Defective ring frame drafting and bad piecing Improperly clothed top roller clearers.

RECTIFICATIONMachine surfaces to be maintained clean.

1. Proper functioning of pnemafil/roller clearers to be ensured.

2. Broken teeth gear wheel to be avoided and proper meshing to be

ensured.

3. Better fiber individualization at cards to be achieved.

Measurable by Uster Imperfection Indicator and observable on appearance

EFFECTEccentric top and bottom rollers

•Insufficient pressure on top rollers •Worn and old aprons and improper apron spacing •Improper meshing of gear wheels •Mixing of cottons varying widely in fiber lengths and use of immature cottons

CAUSES Eccentric top and bottom rollers Insufficient pressure on top rollers Worn and old aprons and improper apron spacing Improper meshing of gear wheels Mixing of cottons varying widely in fibre lengths and use of immature cottons

RECTIFICATIONEccentric top and bottom rollers to be avoided

1. Top arm pressure checking schedules to be Maintained strictly 2. Wide variation in the properties of cottons used in the mixing to be avoided 3. Better fiber individualization at cards to be achieved. 4. Correct spacers to be utilized

Yarn which is weak indicating lesser twist

EFFECT:

More end breaks in subsequent processes

•Shade variation in dyed fabrics

CAUSES:Slack tapes dirty jockey pulleys

Less twist in the yarn

Bad clearing at the traveller

RECTIFICATION:Vibration of bobbins on the spindles to be avoided

1. Proper yarn clearing to be ensured

2. Periodic replacement of worn rings and travellers to be effected

Yarn stained with oil

EFFECTDamaged fabric appearance

•Occurrence of black spot in fabric

CAUSESCareless oil in the moving parts, over head pulleys etc

Piecing's made with oily or dirty fingers

Careless material handlings

RECTIFICATIONAppropriate material handling procedures to be followed

1. Oilers to trained in proper method of lubrication

2. Clean containers to be utilized for material transportation

Very small snarl-like places in the yarn which disappear when pulled with enough tension or Yarn with spring –like shape

EFFECTMore breaks in winding

•More noticeable in polyester and cotton blended yarns

CAUSES Mixing of cottons of widely differing staple length Closer roller settings Eccentric top and bottom rollers Non optimum temperature and relative humidity in the spinning shed Over spinning of cottons

RECTIFICATIONOptimum top roller pressure to be maintained

1. Mixing of cottons varying widely in fibre length to be avoided

2. Use of optimum roller settings

3. Use of properly buffed rollers free from eccentricity to be

ensured

Short thick place