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Defected and Defect-free Fabric..
What is a Fabric Defect?
A Fabric Defect is any abnormality in the Fabric that
hinders its acceptability by the consumer.
What is a Defect-Free Fabric?
1. A Fabric that exhibits a consistent performance within
the boundaries of human use & human view.
2. A Fabric that exhibits a consistent appearance within
the human sight boundaries.
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Measurement of Bias ..
Skew or Bias - Measure the skewin three places spaced as widely
as possible along the length of the
fabric or along a minimum of 1
linear yard. If possible,
make no measurement closer to
the ends of the roll or piece of
fabric than 1 yard. Draw a line
perpendicular to the selvage
across the fabric from a point C
where the marked yarn or course
meets one selvage, meeting the
other selvage at point B. Measure
the distance between points A and
B or D and B, and B and C, as
shown in Fig. 2. Record the threeor more skew or bias
measurements. Calculate the
maximum skew or bias as a
percentage of the fabric width
using the equation:
"% Skew = Distance AB or DB x 100 /
width BC"
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Machine-Related Factors:
Failure of spinning preparation to eliminate or minimize short
and long-term variation Failure of opening and cleaning machines to completely
eliminate contaminants and trash particles
Failure of the mixing machinery to provide a homogenous blend
Excessive machine stops particularly during spinning
Excessive ends piecing during spinning preparation
Poor maintenance and housekeeping
Knitting-related defects
Dyeing and Finishing-related defects
What are the factors that
could lead to fabric defects?
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Material-Related Factors:
Fiber contaminants
Excessive neps and seedcoat fragments Excessive short fiber content
Excessive trash content
High variability between and within-mix
Clusters ofunfavorable fiber characteristics
Weight variation
Twist variation
Excessive Hairiness
What are the factors that
could lead to fabric defects?
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Some other Fabric Defects..
Small bits of
contaminants spun
into the yarn
Whitespecs
Synthetic fibre
contaminant
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Pointers focussing on the Defected area..
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Another Fabric Defect..
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Another Fabric Defect..
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Knit-in Contaminants..
There can be certain defects
which arise during the knit-in
process thus are shown here.
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Modelling Fabric Defects-The
Problem Theory..
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DEFECTS SEVERITY Barre Usually major
Askewd or bias Could be major or minor
Birdseye Major
Bowing Major or minor
Broken colour pattern Major
Crease streak Major or Minor
Drop stitches Major
End Out Usually Major
Hole Major
Missing Yarn Major
Mixed Yarn Major
Needle Line Major or Minor
Pin Holes Major
Runner Major
Slub Major or Minor
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Industry Practise..
PURPOSE
To establish a uniform method for determining, quantifying and measuring
the quality of warp knit elastomeric fabrics; and a method for measuring
length, width, and other physical properties.
METHOD Four-Point System - Penalty points are attributed to a piece of fabric
according to the length of its defects measured in inches. The following
schedule of penalty points is based on fabrics 60/62 inches in width for
defects visible when inspected on face side of fabric only:
Length of Defects:3 inches or less
Over 3, but not over 6 inches
Over 6, but not over 9 inches
Over 9 inches
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Industry Practise..
Number of Penalty Points
1
2
3
4
Four penalty points per linear yard are the maximum assessable for fabrics
up to 60/62 inches in width.
For fabrics over 60/62 inches in width, maximum allowable penalty pointsare to be increased in proportion as the width exceeds 60 inches.
Regardless of the length of fabric, the quality shall be expressed in the
number of penalty points per 100 yard length. (Example: A 40-yard piece
width six penalty points is to be rated as 15 points per 100 yards.)
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Industry Practise..
Identification and Rating Defects:
Examples of defects in evaluating quality are these:
Knitting defects, including holes other than pinholes
Grease/oil spots
Dye spots
Stains
Slubs-except where they are an inherent part of the yarn
Picks
Bowing and Skewing (bias): bowing and skewing may not exceed 5% of overall
width. Examples: 60" width - 3" tolerance and 72" width - 3.5" tolerance
Any yard containing bowing or skewing in excess of these limits shall be penalized
four points.
Fabrics are to be examined for these defects only on the agreed upon selling face
(which may be the technical face, or technical back).
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Facts about Fabric Defects..
99% of Fabric-Defects can be diagnosed with minimum or no testing if
every involved personnel from the fiber to the fabric sector is willing to
honestly tell his/her side of the story. Fabric-defect diagnostic work has
become more of detective work because of missing facts.
Poor Cotton Mixing is a Sure Defect-Causing Factor & Good Mixing alone
does not always guarantee a Defect-Free Fabric. Machine-Related Factors
cannot be emphasized enough.
High cost yarn testing equipments available today reveal minimum or no
prediction of potential fabric defects. Indeed, there is a significant gap
between yarn quality as tested in the yarn raw form and corresponding
yarn quality as it exists in the fabric.
There is a great loss of fabric as well as money due to fabric defects so
care should be taken to minimize them as much as can be done.
Fabric faults or defects are responsible for nearly 85% of the defects foundin the garment industry.
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Current Usual method of Detection and
Optimal measure..
Present Scenario-
Inspection is done manually, ie., when a significant
amount of fabric is produced,the fabric roll isremoved from circular knitting machine and then
sent to an inspection frame.
Optimal Solution-
To automatically inspect fabric as it is being produced
and to encourage maintainence personnel to prevent
production of defects or to cahnge process
parameters automatically and consequently improvefabric ualit .
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Flowchart of Defect
Segmentation..
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On-line Fabric Defect Detection..
Circular Knitting Machine
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..THANK YOU..