Faults in the Knitted Fabrics (part 6)

FabricPress Off
Definition:
Fabric press off appears as a big or small hole in the fabric caused due to the interruption of the loop forming process as a result of the yarn breakage or closed needle hooks.

Press off takes place, when the yarn feeding to both the short butt & long butt needles suddenly stops due to the yarn breakage.

At times complete fabric tube can fall off the needles if the needle detectors are not functioning or are not properly set.

Causes:

• End breakage on feeders with all needles knitting.
• Yarn feeder remaining in lifted up position due to which the yarn doesn’t get fed in the hooks of the needles.

Remedies:

• Needle detectors, should be set precisely to detect the closed needles & prevent the fabric tube from completely pressing off.
• Proper yarn tension should be maintained on all the feeders.

SurfaceHairiness & Piling
Definition:
Surface hairiness appears in the form of excess superfluous fibers, on the surface of the knitted fabrics, which have either been reprocessed, or tumble dried.

Pilling appears as, small fiber balls formed on the fabric surface, due to the entanglement of loose surface fibers.

Factors such as, the fiber staple length, low T.P.M. & fabric construction (with long yarn floats) etc. also contribute to pilling.

Causes:

• Abrasion due to the contact with rough surfaces
• Excessive surface hairiness caused, due to the abrasive tumbling action
• Fabric friction in the Tumble Dryer
• Rough Dyeing process & abrasive machine surfaces (Soft Flow Machine tubes, Tumble Dryer drum etc.)
• Reprocessing of the fabric is, also a major cause of piling.

Remedies:

• Avoid using the Tumble Dryer.
• Control shrinkage by maximum fabric relaxation & over feed in the processing.
• Regularly inspect the fabric contact points on all the machines, for any rough & sharp surface.
• Avoid repeated reprocessing of the fabrics.
• Use anti pilling chemical treatments for the fabrics prone to pilling.

Snagging
Definition:
Snagging appears on the knitted fabric surface as a pulled up yarn float showing up in the form of a large loop.

Causes:

• Caused by the pulling or the plucking of yarn from the, fabric surface, by sharp objects.

Remedies:

• Inspect & rectify the fabric contact points on all the machines (Soft Flow Dyeing, Tumble Dryer & Centrifuge etc), on which snagging is taking place.

Bowing
Definition:
Bowing appears as rows of courses or yarn dyed stripes forming a bow shape along the fabric width.

Causes:

• Uneven distribution of tensions across the fabric width while dyeing or finishing the fabric.

Remedies:

• Bowing can be corrected by reprocessing the fabric by feeding it from the opposite end.
• A special machine (MAHLO) is also available for correcting the bowing in the knitted fabrics.

DyeingPatches
Definition:
Dyeing patches appear, as random irregular patches on the surface of dyed fabrics.

Causes:

• Inadequate Scouring of the grey fabric is one of the primary causes of the dyeing patches.
• Improper leveling agent is also one of the causes of dyeing patches.
• Correct pH value not maintained.
• Dyeing machine stoppage due to power failure or the fabric entanglement in the dyeing machine are a major cause of the dyeing patches.

Remedies:

• Scour the grey fabric thoroughly to remove all the impurities from the fabric before dyeing.
• Use appropriate leveling agents to prevent patchy dyeing.
• Maintain the correct pH value during the course of dyeing.
• Use a power back up (Inverter) for the dyeing operation to be completed uninterrupted.

SoftenerMarks
Definition:
Softener marks appear as distinct irregular patches in the dried fabric after the application of softener.

Causes:

• Softener not being uniformly dissolved in water

Remedies:

• Scour the grey fabric thoroughly to remove all the impurities from the fabric before dyeing.
• Ensure that the softener is uniformly dissolved in the water & doesn’t remain un-dissolved as lumps or suspension.
• Use the right softener & the correct procedure for the application.
• Maintain the correct pH value of the softener before application.

Stains
Definition:
Stains appear as spots or patches of grease oil or dyes of different color, in a neat & clean finished fabric surface.

Causes:

• Dyeing Machine not cleaned thoroughly after dyeing a lot.
• Grease & Oil stains from the unguarded moving machine parts like; Gears Shafts Driving Pulleys & Trolley wheels etc.
• Fabric touching the floors & other soiled places during transportation, in the trolleys.
• Handling of the fabric with soiled hands & stepping onto the stored fabric with dirty feet or shoes on.

Remedies:

• Wash & clean the dyeing machine thoroughly after dyeing every dye lot.
• Follow the dyeing cycle of Light- Medium- Dark shades & then the reverse the cycle while dyeing the fabric.
• All the lubricated moving machine parts should be protected with safety guards.
• Make sure that the fabric is neatly packed in or covered with Polythene sheets while transporting or in storage.
• Handle the fabric carefully with clean hands & do not let anyone step onto the stored fabric.

ColorFading (Poor Color Fastness)
Definition:
The color of the garment or the fabric appears lighter & pale in comparison to the original color of the product after a few uses.

Causes:

• Dyeing recipe i.e. the poor fixing of the dyes is a major cause of color fading.
• Using the wrong combination of colors in a secondary or tertiary shade.
• Use of strong detergents & the quality of water are also the common causes for color fading.
• Prolonged exposure to strong light will also cause the colors to fade.
• High level of acidity or alkalinity in the perspiration of individuals also causes color fading.

Remedies:

• Use the correct dyeing recipe i.e. the appropriate leveling, fixing agents & the correct combination of dyes.
• Follow the wash care instructions rigidly.
• Use mild detergents & soft water for washing the garments.
• Don’t soak the garments for more than 10- 15 minutes in the detergent prior to washing
• Turn the wet garments inside out while drying.
• Dry in shade & not in direct sunlight.
• Protect the garments against prolonged direct exposure to strong lights (show rooms or exhibitions etc.).

ShadeVariation
(Roll to roll & within the same roll)

Definition:
Sometimes there appears to be a difference in the depth of shade between the roll to roll & from place to place in the same roll. The defect will show up clearly in the garments manufactured from such fabric.

Causes:

• Shade variation can be as a result of mixing of the, fabrics of two different lots.
• Shade variation is also caused, by the variation in the process parameters i.e. Time, Temperature & Speed etc. from one fabric roll, to the other.
• Shade variation can appear to be, in fabrics with GSM variation, caused due to the uneven stretching, unequal fabric overfeed % etc.

Remedies:

• Ensure that the grey fabric used for one shade is knitted from the same lot of the yarn.
• Ensure that the same process parameters (Width, Overfeed, Temperature & Machine Speed etc.) are used for each roll of a dye lot.

TonalVariation
Definition:
Roll to roll or within the same roll difference in the color perception i.e. Greenish, Bluish, Reddish or Yellowish etc. is attributed as tonal variation in the shade.

Causes:

• Wrong Dyeing recipe
• Wrong leveling agent selection or wrong dyes combinations.
• Improper fabric Scouring.
• Impurities like Oil & Wax etc. not being completely removed in Scouring
• Level dyeing not being done due to the inappropriate leveling agents.
• Variation in the process parameters, e.g. Temperature, Time & Speed etc .

Remedies:

• Use appropriate leveling agents to ensure uniform & level dyeing.
• Scour the grey fabric thoroughly to ensure the removal of all the impurities.
• Ensure that the whole lot of the dyed fabric is processed under uniform process parameters.