textile testing quality and control Fibrograph

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Assignment on
FIBROGRAPH
COURSE CODE: TEX-2031
COURSE TITLE: TEXTILE TESTING & QUALITY CONTROL-1
SUBMITTED TO:
S.M. MASUM ALAM
LECTURER
DEPARTMENT OF TEXTILE ENGINEERING
SUBMITTED BY:
SOWPHIE SAROUR
ID- 2016000400007
BATCH- 31ST
SECTION- 1
DATE OF SUBMISSION: 19TH
DECEMBER 2017

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Introduction:
The fibrograph is an optical instrument employing photovoltaic cells for
scanning samples of parallel fibers and tracing a type of length-
frequency curve. The theory is developed for a sample of parallel fiber
in which the fibers are positioned at random. The geometrical
interpretation of a resulting curve, or fibrograph indicates simple length
and area measurements that gives various average lengths and
statistical quantities. Fibrograph measurements provide a relatively fast
method for determining the length uniformity of the fibers in a sample
of cotton in a reproducible manner. Results of fibrograph length test do
not necessarily agree with those obtained by other methods for
measuring lengths of cotton fibers because of the effect of fiber crimp
and other factors.
Fibrograph tests are more objective than commercial staple length
classifications and also provide additional information on fiber length
uniformity of cotton fibers. The cotton quality information provided by
these results is used in research studies and quality surveys, in checking
commercial staple length classifications, in assembling bales of cotton
into uniform lots, and for other purposes. Fibrograph measurements
are based on the assumptions that a fiber is caught on the comb in
proportion to its length as compared to total length of all fibers in the
sample and that the point of catch for a fiber is at random along its
length. (2)

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Objects:
 To know about the fibrograph machine and its different parts
 To know about its operation process
 To know about measurement of fiber length
 To know about span length
 To maintain the buyer requirements
Apparatus:
 Fibro sampler: fibro sampler is used in later models to clamp the
fibers on the comb. Fiber sample is put inside the cylinder
of sampler. Fiber comb, with 13 needles/inch, is rotated around
the fibro sampler, with pressure applied on the cotton, during
which it picks up fibers projecting from the holes of sampler. The

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instrument is consequently insensitive to the presence of very
short fibres, and in practice the Fibrograph has its origin at a point
representing a length of 0.15 inch (3.8 mm).
 Fibro sampler comb holder
 Fibro sampler perforated cylinder
 Handle (1)
Working principle:
In fibrograph, fiber samples are presented in the form of a pair of
carefully prepared fringes. The light transmitted through these fringes
is monitored byphotoelectric current. The amount of light passing
through the fiber sample is linearly proportional to the number of fibers
in the light path. The changes in the photoelectric current are recorded
graphically in the form of a fibrograph. From this fibrograph various
length parameters of practical interest, such as span length, mean
length, upper-half mean length and index of uniformity, given as the
ratio of mean length and half mean length can be analyzed.(5)
Preparation of test specimen:
 A laboratory sample of weight 100g is selected and from this a
subsample of 25+5g is prepared
 An empty comb is placed in the fibro sampler comb holder with
the teeth pointing upwards
 And with the left hand the sub-sample is placed in the fibro
sampler cylinder and pressed against the curved perforated
sample plate. With a circular motion of the left hand, the fibers
are pressed so that they protrude through the holes of the sample
plate.

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 Then with right hand and operating handle is rotated in the anti-
clock wise direction.
 When the comb holder reaches the lower rest position, the comb
with its fibers is ready for the measurements
 Then the comb is removed and inspected to see that the comb
with the fiber is kept into the fibro sampler comb holder and a
portion of sub sampler is placed in the fibro sampler cylinder
 Then the operating cylinder is given one complete rotation in the
anti-clock wise direction and the comb is removed and inspected
for the uniform distribution of fibers on the comb teeth
 The card clothing on the fibro sampler is cleaned after the
preparation of each board in order to maintain effective combing
action
 A servo-follower system connected to the photo electric cells
indicates on the amount counter the relative number of fiber is
the sample board at the point where the light beam passed
through them.
 A servo computer remembers the number of fiber at the 0.15 inch
distance from the centre of the comb teeth and computes the
number of fibers corresponding to the different span length
 When a span length is selected the comb carrier move unit the
number of fiber under the lighthouse is equal to the number of
fiber corresponding to that span length
 The span length is than indicated by the length counter which
indicates the movement of the comb carrier in inches (6)

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From the value of 50% span length and 2.5% span length uniformity
ratio can be calculate as,
Percentage of short fibers whose length is less than .5 inch can also be
determined push button in the digital fibrograph,using the formula.
Classification of cottons according to staple length and span length
values:
NO. Category Staple length range in mm
01. Short 19 and below
02. Medium 20 to 21.5
03. Superior of medium 22 to 24
04. Long 24.5 to 26
05. Superior long 27 and above
a. Superior long staple- staple length between 27 and 29.5mm.
b. Extra long staple length- 30mm and above.
According to 2.5% span length values cotton is classified into the staple
length categories as follows:
NO. Category 2.5% span length in inch
01. Short Below 1.00
02. Medium 1.00 to 1.14
03. Long 1.15 to 1.29
04. Extra long Above 1.29

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Graphically fibrograph:
Digital fibrograph may be analyzed graphically to yield various
length parameters of interest to the producers and users of cotton. The
tangent to the curve at its starting point A cuts OY at P and OX at M.
Then OM is the mean length of the fibers in the original population
longer than 0.15 inch (3.8 mm). If OP is bisected at Q and the tangent to
the curve from Q cuts OX at R, then OR is the upper-half mean length,
UHML, and the ratio of OM to OR is a valid index of uniformity.(4)

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Merits:
1. Simulates beard formed by fibres held by back or front roller nip of
a drafting system
2. Very rapid (about 1 - 4 min per sample)
3. Does not depend much upon operator skill.
Limitation:
1. Because of fibre breakages and length involved in clamping,
estimates of length are lower.
2. Holding length calculated mathematically is found to be around 4.06
mm8. Scanning starts at 3.81 mm from comb. As a result actual
scanning starts at 7.87 mm from the comb because of this. The holding
length also varies from cotton to cotton. Krowwicki and Ramay showed
that 50 % span length, 2.5 % span length and Uniformity ratio in Digital
Fibrograph are overestimated as scanning starts at 3.81 mm from
clamping point. 50 % and 2.5 % span lengths are overestimated to the
extent given below:
50% span length = 0.5 L + 1.905
2.5 % span length = 0.975 L + 0.09525
Maximum possible Uniformity Index is increased as a result from 51.28
to 57.6 for 30 mm and 51.28 to 56 for 40 mm cotton. The extent to
which fibrogram is affected by scanning at 4 mm from clamp position
instead of clamp is shown in Fig 1 and Table 1 below. Both 2.5% and 50
% span length are increased but the effect is more on the latter. As a
result uniformity Index is increased.(2)

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Fig 1 : Comparison of Fibrograms with scanning from clamp and scanning from 4mm length
Table-1: Span lengths and uniformity ratios with scanning from clamp
and scanning from 4mm length
Span length Scanning from clamp(mm) Scanning 4mm from clamp
2.5% 31.67 32.05
50% 12.03 14.32
UI% 40 44.7
3. Crimp in the fibre leads to underestimation.
4. Highly unreliable for estimating short fibre content. Precautions
required in fibre sampler for getting reliable beards are discussed by
Carpenter10. 1 Even pressure should be applied on the sample inside

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cylinder 2. The cylinder should be rotated slowly and gently 3 at least
one half of perforations should be covered by sample 4 beard should be
uniform without thick and thin places 5 A fresh sample surface should
be used for each comb 6. Excessive brushing of beard should be
avoided. Yoakum11 reported a higher fibre length with fibro sampler
beards than hand prepared beards. Correlation of yarn strength with
2.5 % span length is as good as the upper quarter length of comb sorter
and upper half mean of servo fibrograph. 2.5 % span length by digital
fibrograph and short fibre % by comb sorter were better related to ring
frame end breakage rate than uniformity ratio by servo fibrograph.(1)
Conclusion:
After completing the experiment we can learn about the samples of
parallel fibers and can be able to tracing a type of length-frequency
curve. Beard of fibres is prepared by picking the fibres randomly from
the sample by a comb and loose fibres brushed aside. The beard is
optically scanned from the base to tip. The comb has 28 needles/inch.
Since long fibres have a proportionally higher probability to be caught
by comb this results in a length biased sample. The instrument based
on this principle was developed to accurate the calculation.(3)

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References:
1. https://www.slideshare.net/tahmidurrahman52/fibrograph
2. http://textilelearner.blogspot.com/2015/07/merits-and-
limitations-of-cotton-fiber-part-1.html
3. http://www.tandfonline.com/doi/abs/10.1080/004050097086585
42
4. https://textilestudycenter.com/fibrograph-method/
5. http://journals.sagepub.com/doi/abs/10.1177/004051755802800
612?journalCode=trjc
6. Lecture sheet.