Yarn, fabric Defects And Fabric blends APAREL DESIGNING AND CONSTRUCTION, SEMESTER II
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.