This presentation contain about fiber length and various type of length and also the ways to measure span length , effective length,mean length etc.

1. DEPARTMENT
OF
TEXTILE
PRESENTATION ON
FIBRE LENGTH

2. Why fibre length?
• Quality assessment, Fibre breakage study, machine
settings, combing efficiency, etc.
• Length of staple fibre is one of the most important
characteristics. In general a longer average fibre length is
to be preferred because it confers a number of
advantages. Firstly, longer fibres are easier to process.
Secondly, more even yarns can be produced from them
because there are less fiber ends in a given length of
yarn. Thirdly, a higher strength yarn can be produced
from them for the same level of twist.
• The length and fineness are sometimes related in
natural fibres whereas for man-made fibres, length and
fineness can be controlled separately.

3. DEFINITIONS OF FIBRE LENGTH PARAMETRES:-
• Mean length : The arithmetic mean of the length
of all the fibres present in a small but representative
sample of cotton, based on weight-length
distribution or relative number-length distribution.
• Upper Quartile Length: The length for which 75
per cent of all the observed values are lower and 25
per cent higher, by weight or by number

4. • Effective Length : It is difficult to give a clear
scientific definition for effective length. It may be
defined as the upper quartile of the numerical length
distribution from which some of the shortest fibres
are eliminated by an arbitrary construction. The
fibres eliminated are those shorter than half the
effective length.
• Span Length : The distance spanned by a
specified percentage of the fibres in the test
beard. 2.5% span length is the distance from the
clamp on a fibre beard to a point upto which only
2.5% of the fibres extend.

5. MEASUREMENT OF FIBRE LENGTH :-
• 1. HAND STAPLING METHOD.
• 2. COMB SORTER METHOD.
• 3. PHOTO ELECTRIC METHOD (FIBRO GRAPH).
• 4. SHIRLEY PHOTO ELECTRICAL METHOD.
• 5. WIRA FIBRE LENGTH MACHINE.

6. HAND STAPLING METHOD :
(By trained classers)
• Selecting a sample and preparing the fibres by hand doubling
and drawing to give a fairly well straightened tuft of about ½
inch wide.
• This is laid on flat black background and the staple length is
measured.
• The shorter fibres will lie in body of the tuft and extreme ends
(tips) will not be the limits used for measurement of staple
length.
• The classer chooses the length where there are reasonably
well defined edges
• Subjective in nature, so difference in results between classers.

7. Comb Sorter Method:

8. In the diagram
OQ = 1/2 OA
OK = 1/4 OP
KS = 1/2 KK’
OL = 1/4 OR
Short fibre percentage = (RB/OB) × 100%
LL’ = Effective length (because many m/c settings are
related with this length)
LL’-MM’ = NL’=Inter-quartile range
Dispersion% = NL’/LL’
(For flatter middle zone, dispersion is minimum)
Frequency distribution in opposite way, i.e. the curve is
known but the frequency distribution is to be obtained.

10. Comb sorter diagram analysis:
Staple length US'' + 3/32'' = EL'' (34/32'' -
39/32'')
Staple length US''+ 1/8'' = EL'' (longer cotton)
Staple length US'' + 1/16'' = EL'' (shorter cotton)
Staple length US'' = 0.91 × EL''
Staple length Uk''- 1/32'' = EL'' (long staple)
Staple length Uk'' + 1/32'' = EL'' (medium staple)
Mean length
(x 1/8) in.
= (Sum of base line readings / Base
line length)
= (453.2 / 64) = 7.1
Mean length
(x 1/32 in.)
= 4 x 7.1 = 28.4

11. Photoelectric method (Fibro graph):
• Optical method of measuring the density along the
length of a tuft of parallel fibres.
• Samples are prepared by “fibro sampler”.

14. • The point where it is caught is at random along its
length.
• Distance traveled from base line
• Floating fibre (%) = [2.5%SL / L – 0.975} × 100
• U.R. = (50%SL / 2.5% SL) × 100 [apprx. 40-50% for
normal cotton]
• Where L = avg. length of fibre

15. Shirley photoelectric stapler:
• For quicker measurement of length (staple length).
• Objective measuring technique of earlier staple
length measuring method. (Classer judges by eye).

17. WIRA MACHINE :
The WIRA fibre length machine [13] is an attempt to automate
the proces of single fibre measurement and is intended
mainly for measuring wool fibres. The equipment shown in
Fig. 3.11 involves a rotating shaft with a spiral groove
machined in it. One end of the fibre to be measured is gripped
by a pair of tweezers whose point is then placed in the moving
spiral. This has the effect of moving the tweezers to the right
and so steadily drawing the fibre through the pressure plate.
This ensures that the fibre is extended under a standard
tension. A fine wire rests on the fibre and is arranged so that
when the far end of the fibre passes under the wire it allows it
to dropinto a small cup of mercury and thus complete an
electrical circuit.

18. causes the shaft to stop moving, so halting the
tweezers; at this point the tweezers are then raised to
lift the counter immediately above where it has
stopped. The counters are arranged in 0.5 cm sections
and each time one is lifted it adds a unit to the
appropriate length group so contributing to a
cumulative total.

20. THANK YOU