Faults in the Knitted Fabrics (part4)

Snarls
Definition:
Snarls appear on the fabric surface in the form of big loops of yarn getting twisted due to the high twist in the yarn.
Causes:

• High twist in the yarn.

Remedies:

• Twist in the yarn should be in required TPM.

Contaminations
Definition:
Contaminations appear in the form of foreign matter such as; dyed fibers, husk, dead fibers etc. in the staple spun yarn or embedded in the knitted fabric structure.
Causes:

• Presence of dead fibers & other foreign materials, such as; dyed fibers, husk & synthetic fibers etc.
• 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:

• Use rich fiber mixing for the yarns to be used for Knitting in order to have less dead fibers appearing in the fabric.
• Rigid control measures in the Blow Room to prevent the mixing of foreign matters in the Cotton mixing.
• 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
Definition:
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.

Causes:

• High T.P.I. of the Hosiery Yarn
• Uneven Fabric tension on the Knitting machine.
• Unequal rate of Fabric feed on the Stenter, Calender & Compactor machines.

Remedies:

• Use the Hosiery yarns of the recommended TPM level for Knitting.
• Ensure uniform rate of feed of the dyed fabric on both the edges while feeding the fabric to the Calender, Compactor or Stenter machines.

Faults in the Knitted Fabrics (part 3)

FinishingRelated Defects:
Defects caused mainly due to the wrong process parameters are;

1. High Shrinkage
2. Skewing
3. Spirality
4. Surface Hairiness & Pilling
5. Tonal variation
6. Snagging (Sharp points in the dyeing machine or trolley etc)
7. Fold Marks
8. Wet Squeezer Marks
9. GSM variation
10. Fabric Width variation
11. Curling of S.J. Fabrics

DropStitches (Holes)
Definition:
Drop Stitches are randomly appearing small or big holes of the same or different size which appear as defects in the Knitted fabrics.

Hole in fabric

Major Causes:

• High Yarn Tension
• Yarn Overfeed or Underfeed
• High Fabric Take Down Tension
• Defects like Slubs, Neps, Knots etc.
• Incorrect gap between the Dial & Cylinder rings.

Remedies:

1. Ensure uniform yarn tension on all the feeders with a Tension Meter.
2. Rate of yarn feed should be strictly regulated as per the required Stitch Length.
3. The fabric tube should be just like a fully inflated balloon, not too tight or too slack.
4. The yarn being used should have no imperfections like; Slubs, Neps & big knots etc
5. The gap between the Cylinder & the Dial should be correctly adjusted as per the knitted loop size.

Barriness
Definition:
Barriness defect appears in the Knitted fabric in the form of horizontal stripes of uniform or variable width.

Causes:

• High Yarn Tension
• Count Variation
• Mixing of the yarn lots
• Package hardness variation

Remedies:

• Ensure uniform Yarn Tension on all the feeders.
• The average Count variation in the lot should not be more than + 0.3
• Ensure that the yarn being used for Knitting is of the same Lot .
• Ensure that the hardness of all the yarn packages is uniform using a hardness tester.

Streakiness
Definition:
Streaks in the Knitted fabrics appear as; irregularly spaced & sized, thin horizontal lines.

Causes:

• Faulty winding of the yarn packages.
• Yarn running out of the belt on the Pulley

Remedies:

• Winding of the yarn package should be proper.
• The yarn should be running between the belt and around the pulley.

Imperfections
Definition:
Imperfections appear on the fabric surface in the form of unevenly placed or randomly appearing Knots, Slubs & Neps, Thick & Thin places in the yarn.

Causes:

• Big Knots, Slubs & Neps in the yarn, Thick & Thin yarn.

Remedies:

• Specify the quality parameters of the yarns to be used for production to the yarn supplier.

Faults in the Knitted Fabrics (part 2)

KnittingElements Related Defects:
Almost all the defects appearing in the vertical direction in the knitted fabrics are as a cause of bad Knitting Elements.These defects are mainly;

1. Needle & Sinker Lines
2. Drop Stitches etc.

MachineSettings Related Defects:
These defects appear randomly in the knitted fabrics due to the wrong knitting machine settings &that of the machine parts. The defects are mainly;

1. Drop Stitches
2. Yarn Streaks
3. Barriness
4. Fabric press off
5. Broken Ends
6. Spirality

DyeingRelated Defects:
The Dyeing related defects are as follows;

1. Dyeing patches
2. Softener Marks
3. Shade variation
4. Tonal variation
5. Color fading (Poor Color Fastness)
6. Dull shade
7. Crease or rope Marks

Faults in the Knitted Fabrics (part1)

Faults in the Knitted Fabrics:

A defect of the knitted fabric is an abnormality which spoils the aesthetics i.e. the clean & uniform appearance of the fabric & effects the performance parameters, like; dimensional stability etc.

There are various types of defects which occur in the Knitted fabrics of all types caused by a variety of reasons. The same type of defects may occur in the fabric due to a variety of different causes e.g. Drop Stitches, Spirality etc.

Category of Defects:
Yarn Related Defects:
Almost all the defects appearing in the horizontal direction in the knitted fabric are yarn related. These defects are mainly;

1. Barriness
2. Thick & Thin lines
3. Dark or Light horizontal lines (due to the difference in dye pick up)
4. Imperfections
5. Contaminations
6. Snarling
7. Spirality