Yarn, fabric Defects

And Fabric blends

APAREL DESIGNING AND CONSTRUCTION, SEMESTER II

YARN DEFECTS

Introduction:

Yarn quality is influenced by various types of yarn faults which also affects the quality of

fabric produced. During the yarn manufacturing process various types of irregularities are

generated in the yarn diameter regularly or at intervals which are known as yarn faults .

These faults are mainly categorized as below:

1. Frequently Occurring Faults( Analyzed by Uster Evenness Tester)

2. Seldom Occurring Faults( Scanned by Uster Classimat Tester)

Frequently Occurring Faults;

Thick Places

Thin Places

Neps

Thin places and thick places are produced due to drafting irregularities and neps are

generated due to immature fibers in raw material.

Neps are small, tangled, ball-like masses of fiber. They result from the mechanical

processing of the cotton.

Seldom Occurring Faults;

Slubs

Spun in fly

Long thin places

Slubs- A yarn defect consisting of a lump or thick place on the yarn caused by lint or small.

Lengths of yarn adhering to it.

Spun in fly- Fly or fluff either spun along with the yarn or loosely embedded on the yarn, due

to malfunctioning of humidification point, fanning by workers or accumulation of fluff on

parts of the machine.

Why these yarn faults should be avoided:

Causes breaks during post spinning operations.

Detract aesthetic appeal of the fabric, if allowed to pass.

Objectionable yarn faults can be categorized in three groups:

1. Faults due to raw material

2. Faults due to piecing

3. Faults due to Spinning machine

Bad piecing.

Faults due to raw material: The number of objectionable faults due to raw material varies

from 16% to 30% with different yarns.

Faults due to piecing: The number of objectionable faults due to piecing varies from 9% to

16% of the total objectionable faults.

Faults due to Spinning machine: The spinning frame (R/F) is responsible for about 50%

to 60% of the total objectionable yarn faults.

FABRIC DEFECTS

Fabric faults are responsible for major defects found by the garment industry. Due to the

increasing demand for quality fabrics, high quality requirements are today greater since

customer has become more aware of “Non-quality” problems. In order to avoid fabric

rejection, mills have to produce fabrics of high quality, constantly. Often inspectors are

given the responsibility of inspecting finished garments without adequate training in fabric

defects and their causes. The ultimate solution, of course, is to provide actual examples or

photographs of both major and minor defects.

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.

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

Knitting Elements 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.

Machine Settings 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

Dyeing Related 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

Finishing Related 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

Drop Stitches (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.

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

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

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

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.

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.

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.

Needle Lines

Definition:

Needle lines are prominent vertical lines along the length of the fabric which are easily

visible in the grey as well as finished fabric.

Causes:

Bent Latches, Needle Hooks & Needle stems

Wrong Needle selection (Wrong sequence of needles, put in the Cylinder or Dial)

Horizontal lines

Causes:

Fault in bobbin

Irregular tension on cams.

Broken Needles/ Laddering

Definition:

Defects caused by the broken needles show prominently as vertical lines parallel to the

Wales. There are no loops formed in the Wale which has a broken needle.

Causes:

High Yarn Tension

Bad Setting of the Yarn Feeders

Old & Worn out Needle set

Cylinder Grooves are too tight restricting needle movement

Breakage of hook or butt in needle

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.

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.

GSM Variation

Definition:

The fabric will appear to have a visible variation in the density, from roll to roll or within the

same roll of, the same dye lot.

Causes:

Roll to roll variation in the, process parameters, of the fabric, like; Overfeed & Width

wise stretching of the dyed fabric, on the Stenter, Calender & Compactor machines.

Roll to roll variation in the fabric stitch length.

Measurement Problems

Definition:

The measurements of the garments totally change after, a few hours of relaxation & after

the first wash. The arm lengths or the front & back lengths of the garments may vary, due

to the mix up of the parts.

Causes:

Shrinkage caused due to the inadequate relaxation of the knitted fabrics, before

cutting.

Mixing of the garment parts cut from, different layers or different rolls of the knitted

fabric.

Woven Fabrics Defects or Faults:

1. Bad Selvedge

Causes: A defect in a fabric because of faulty weaving, warp ends being set too far apart

for the thickness of the yarn or in finished fabric, an appearance in which the

underlying structures is not connected to the degree required.

2. Burl Mark

Causes: When a slub or extra piece of yarn is woven into the fabric, it is often removed by a

"burling tool." This will usually leave an open place in the fabric.

3. Drawbacks

Causes: Caused by excessive loom tension gradually applied by some abnormal restriction.

When the restriction is removed the excess slack is woven into the fabric. Usually the ends

are broken.

4. Dropped Pick

Causes: Caused by the filling insertion mechanism on a shuttle less loom not holding the

filling yarn, causing the filling yarn to be woven without tension. The filling yarn appears as

"kinky." There will also be areas of "end out."

5. End out

Causes: Caused by yarn breaking and loom continuing to run with missing end.

6. Jerk-in

Causes: Caused by an extra piece of filling yarn being jerked part way into the fabric by the

shuttle. The defect will appear at the selvage.

7. Knots

Causes: Caused by tying spools of yarn together.

8. Mixed End (Yarn)

Causes: Yarn of a different fiber blend used on the wrap frame, resulting in a streak in the

fabric.

9. Mixed Filling

Causes: Caused by bobbin of lightweight yarn or different fiber blend used in filling. Will

appear as a distinct shade change.

10. Open Reed

Causes: Results from a bent reed wire causing wrap ends to be held apart, exposing the

filling yarn. Will be conspicuous on fabrics that use different colored yarns on wrap and

shuttle.

11. Slub

Causes: Usually caused by an extra piece of yarn that is woven into fabric. It can also be

caused by thick places in the yarn. Often is caused by fly waste being spun in yarn in the

spinning process.

12. Smash

Causes: Caused by a number of ruptured wrap ends that have been repaired.

13. Soiled Filling or End

Causes: Dirty, oil looking spots on the wrap or filling yarns, or on package-dyed yarn.

14. Stop Mark

Causes: When the loom is stopped, the yarn elongates under tension; when loom starts

again' the slackness is woven into the fabric.

15. Thin Place

Causes: Often caused by the filling yarn breaking and the loom continuing to run until the

operator notices the problem.

16. Holes

Causes: Bad needle, take down mechanism too tight, high tension on yarn, bad yarn needle

too tight in their slots, dial height too low or too high, badly tied knots, improper stitch

setting.

17. Drop Stitches

Causes: Takedown mechanism too loose, defective needles, too loose yarn tension not

sufficient, wrong needle timing set, needle tricks closed.

18. Loop Distortion

Causes: Bad and bent needles, bent trick walls, uneven yarn tension, needle timing set

wrong, yarn carriers set wrong.

Faults in Sewed Fabrics:

Seam Pucker:

When the smooth fabric appearance turned wrinkled by the way of seam is called Pucker. It

is generally happened when there is too much fabric and not enough thread in the seam.

Pucker is one of the most repeatedly occurring sewing defects on fabric. Seam puckering

in garments is the combination of many causes. Generally seam puckering in cloth is seen

after sewing and washing.

Reasons of seam puckering:

1. Puckering due to differential fabric stretch

2. Puckering due to differential fabric dimensional instability

3. Puckering due to tension of sewing thread

4. Puckering due to shrinkage of sewing machine

5. Puckering due to structural jamming

6. Puckering due to unmatched pattern

FABRIC BLENDS

Blended fabrics are created when two or more different kinds of fibers are mixed together

to create a new fabric with unique properties. Throughout history, blended fabrics have

been developed to cater to specific needs, combining the attributes of different fibers to

achieve a desired outcome.

The blending of cellulosic fibers with man-made fibers to produce fabrics with improved

characteristics has long been accepted throughout the world. The use of blended fabrics

has been tremendously increased even in India. The price structure and multi-fiber policy of

government have increased the use of cellulosic blended fabrics.

The properties of the fibers blended are combined and made into a modified state in a

blended fabric. If blending is done carefully the good qualities of the fibers are emphasized

minimizing the poor qualities.

Blending requires knowledge of both fiber science and art. It enables the technician to

produce a perfect fabric for perfect use.

Reasons why fabrics are blended

1. The important reason for blending fibers is to produce better performance. By

blending we can improve the characteristics that are poor in one fiber, by blending it

with another type of fabrics that excel in those characteristics For example

polyester when blended with cotton, the resultant fabric has moderate absorbency

which is almost nil in polyester.

2. To improve the texture: Hand or feel and appearance of fabrics blending of wool

fibers with polyester produce the desired texture for suiting materials. Viscose,

when blended with cotton, improves its luster and softness and thereby enhances its

appearance.

3. To reduce the cost: This is sometimes one of the important reasons for blending of

fibers. The cost of a very expensive fabric can often be reduced by blending with

another cheap fiber. For example, expensive wool is blended with cheaper polyester

to reduce the cost.

4. To produce cross-dyed effects: Fibers with unlike dye affinity are combined and dyed

together so that it produces interesting cross dyes effects as one fiber take up

the color and the other retains its original color.

5. To improve the spinning, weaving and finishing efficiency for example the spinning

efficiency of polyester is improved by blending with cotton to produce spun yarns.

Blending may be done before or during spinning. It can be done at the opening and blending

stage. Though it facilitates perfect blending it poses problems and so it is not of much use.

Even at the sliver stage overdrawing or roving or spinning frames blending can be done.

Blending overdrawing frame is most commonly used today. Slivers of different fibers are

combined overdrawing frame depending on blend ratio. They are drawn to get single silver

which is later processed into yarn.

Types of Blended Fabrics

Among the various types of blends available today, the most popular fabrics are terry

cotton, terry wool, and polyester viscose. Polyester cotton viscose blends are most

common. Various effects and combinations of properties are produced from these blends

depending on the fibers used and the percentage of these fibers used in each

blend

Terry Cotton

Fabrics of various blend ratios are available in the market today. A blend of 65% polyester

and 35% cotton is common. The other blend ratios are 67/33, 70/30, 50/50, 45/55, 52/48,

80/20 polyester and cotton respectively is also available.

A blend of 65/35 polyester and cotton produces satisfactorily a fabric for daily wear. 59/50

blend produces softer and more absorbent fabric. Polyester, when blended with cotton,

contributes more strength wrinkle resistance and shape; retention, cotton produces

comfort as it provides absorbency and heat conduction. The polyester cotton

a blend is most suited for not only India but also for other tropical countries.

Terry-wool Suiting Fabrics

The excellent shape retention of polyester is the foremost contribution to worsted fabrics

which show poor shape retention.

Polyester provides excellent wrinkle resistance and crease retention that contributes to

shaping retention whether wet or dry. Depending on the blend ration polyester increases

the strength of wool fabrics. Wool provides warmth resiliency, drapability, and absorbency

depending on the blend ratio.

Blends of polyester and wool are available in ranges from 65% polyester and 35% wool to

60/50, 55/45, 5/50 respectively. A blend of 65/35 will be suitable to produce a light weight,

all season suiting. For medium worsteds 60/40 blend is suitable. When more warmth is

required 50/50 blends should have opted.

Polyester Viscose Rayon

The blend of polyester with viscose contributes durability, resiliency and shape retention.

The wet strength of the resultant fabric is also improved, viscose provides absorbency, soft

texture, and variety of color. A blend of polyester and viscose generally ranges from 65%

of polyester and 35% viscose to 55/45, 45/55, 48/52 respectively. Among these blend levels,

48/52 and 65/35 are commonly used for school

uniforms and suiting materials.