Most Common Knitted Fabric Faults and Their Remedies

 Knitted Fabric Faults and Their Remedies:

 

Drop Stitches (Holes):

Drop Stitches are randomly appearing small or big holes of the, same or different size, which appear as defects, in the Knitted fabrics.

Fig 1 : Drop Stitches(Holes)

Causes:

1.          High Yarn Tension
2.          Yarn Overfeed or Underfeed
3.          High Fabric Take Down Tension
4.          Obstructions in the yarn passage, due to the clogging of eyelets, yarn guides & tension discs, with wax & fluff etc.
5.          Defects like; Slubs, Naps, Knots etc.
6.          Incorrect gap between the Dial & Cylinder rings.

Remedies:

Ensure uniform yarn tension on all the feeders, with a Tension Meter.

Rate of yarn feed should be strictly regulated, as per the required Stitch Length.

1.          The fabric tube should be just like a fully inflated balloon, not too tight or too slack.
2.          Eyelets & the Yarn Guides, should not have, any fibers, fluff & wax etc. stuck in them.
3.          The yarn being used, should have no imperfections, like; Slubs, Neps & big knots etc
4.          The gap between the Cylinder & the Dial should, be correctly adjusted, as per the knitted loop size.

 

Barriness:

Causes:

1.         High Yarn Tension
2.          Count Variation
3.          Mixing of the yarn lots
4.          Package hardness variation

Remedies:

1.          Ensure uniform Yarn Tension on all the feeders.
2.          The average Count variation in the lot, should not be more than +- 0.3
3.          Ensure that the yarn being used for Knitting is of the same Lot / Merge no.
4.          Ensure that the hardness of, all the yarn packages, is uniform, using a hardness tester.

 

Streakiness:

Causes:

1.        Yarn slippage on the IRO Pulley, due to the yarn slipping in & out from underneath the IRO Belt, due to a tilted IRO Pulley.
2.          Worn out IRO belts, yarn guides & eyelets etc
3.          Faulty winding of the yarn packages
4.          Yarn running out of the belt, on the IRO Pulley.

Remedies:

1.          Ensure very smooth, clean & obstruction free passage of the yarn, through the eyelets, yarn & tension discs etc.
2.          No cuts or rough surfaces, in the Porcelain Eyelets, Yarn Guides & the Yarn Feeder holes etc.
3.          Flawless winding of the, Yarn Package (The yarn coils should unwind smoothly, without any obstruction)
4.          The yarn should be running under the IRO belt, between the belt & around the IRO pulley.

 

Snarls:

 Snarls appear on the fabric surface, in the form of big loops of yarn getting twisted, due to the high twist in the yarn (Unbalanced twist yarn).

Causes:

1.          High, twist in the, yarn.
2.          Hosiery yarns are soft twisted. High, twist in the yarn, is the cause of snarling.
3.          Snarls cause, fabric defects & needle breakages

Remedies:

1.       .     Ensure using Hosiery Yarns, of the recommended T.P.M. only.
2.             Hold a few inches of the yarn in both the hands, in the form of a ‘U’.
3.            The yarn has a balanced twist, if it doesn’t tend to rotate or turn, in the form of a snarl.
4.             Such yarn can be used for Hosiery applications.

Contaminations:

Causes:

1.         Presence of dead fibers & other foreign materials, such as; dyed fibers, husk & synthetic fibers etc.
2.          Dead Fibers appear in the fabric, as a result of the, presence of excessive immature Cotton fibers, in the Cotton fiber crop.
3.          Dead fibers do not pick up color during Dyeing.
4.          Presence of the foreign materials, in the, staple fiber mixing
5.          Kitty, Husk, Broken Seeds, dyed fibers & fibers like Poly Propylene, Polyester, Viscose etc
6.          Dyed & other types of fibers flying from the adjacent Knitting machines cling, to the yarn being used for knitting & get, embedded in the Grey Fabric.

Remedies:

1.          Use rich fiber mixing for the yarns, to be used for Knitting, in order to have less dead fibers, appearing in the fabric.
2.           Rigid control measures in the Blow Room, to prevent the mixing of foreign matters in the Cotton mixing.
3.          Segregate the Spinning & Knitting Machines, with Plastic Curtains or Mosquito Nets, to prevent the fibers flying from the neighboring machines, from getting embedded in the yarn / fabric.

 

Spirality:

Spirality appears in the form of a twisted garment, after washing. The seams on both the sides of the garment displace, from their position & appear on the front & back of the garment.

Fig 2 : Spirality

Causes:

1.          Spirality is caused, by the Twisting Torque as a result, of the high yarn T.P.M.
2.          Hosiery yarns are soft twisted, whereas the Warp yarns are hard twisted
3.          Uneven Fabric Take down tension, on the Knitting machine.
4.          Unequal rate of Fabric feed on the Stenter, Calender& Compactor machines.

Remedies:

1.          Use the Hosiery yarns of the recommended TPM level for Knitting
2.          Hosiery yarns are soft twisted, in comparison to the Warp yarns
3.           Fabric pull or the Take Down tension, on both sides of the grey fabric tube, on the knitting machine, should be equal.
4.           Ensure uniform rate of feed of the dyed fabric, on both the edges, while feeding the fabric to the Calendar, Compactor or Stenter machines.

Needle Lines:

Causes:

1.          Bent Latches, Needle Hooks & Needle stems
2.          Tight Needles in the grooves
3.          Wrong Needle selection (Wrong sequence of needles, put in the Cylinder or Dial)

Remedies:

1.          Inspect the grey fabric on the knitting machine for any Needle lines.
2.          Replace all the defective needles having, bent latches, hooks or stems.
3.          Remove the fibers accumulated in, the Needle tricks (grooves).
4.          Replace any bent Needles, running tight in the tricks.
5.          Check the Needle filling sequence in the Cylinder / Dial grooves (tricks).

 

Sinker Lines:

Causes:

1.          Bent or Worn out Sinkers
2.          Sinkers being tight in, the Sinker Ring grooves

Remedies:

1.          Replace, all the worn out or bent sinkers, causing Sinker lines in the fabric.
2.          Sinker lines are very fine & feeble vertical lines, appearing in the fabric.
3.          Remove the fibers, clogging the Sinker tricks (Grooves)

 

Oil Lines:

Causes:

1.  Fibers & fluff accumulated in the needle tricks, which remain soaked with oil.
2.  Excessive oiling of the, needle beds.

Remedies:

1.          Fibers, accumulated in the needle tricks, cause the oil to seep into the Fabric.
2.          Some lubricating oils are not washable & cannot be removed during Scouring.
3.          Oil lines appear in the fabric, in the lengthwise direction, even after dyeing.
4.          Remove all the Needles & the Sinkers of the machine, periodically.
5.          Clean the grooves of the Cylinder & Dial of the machine thoroughly, with petrol.
6.          Blow the grooves of the Cylinder, Dial & Sinker ring, with dry air after cleaning.

 

Surface Hairiness & Piling:

Causes:

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

Remedies:

1.          Avoid using the Tumble Dryer.
2.          Control shrinkage by maximum fabric relaxation & over feed in the processing
3.          Regularly inspect the fabric contact points on all the machines, for any rough & sharp surfaces.
4.          Rectify, if found rough
5.          Avoid repeated reprocessing of the fabrics.
6.          Use anti pilling chemical treatments for the fabrics, prone to pilling.

Bowing:

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

Causes:

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

Remedies:

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