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Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 1
Abstract : - Cotton is a natural fibre available easily and abundant quantity. It is a
most suitable fibre for textile spinning & clothing due to it’s good spinnability &
human friendly characteristics. As cotton is a natural fibre hence it’s properties also
affected with several other factors which create variation in fibre properties, these
variations also affect spinning processes & it’s products Quality in multi dimensions.
Each fibre characteristic impact individually and collectively on spinning process or at
ultimate product quality. Revolutionary changes observed in last two decade in the
field of spinning machineries where processing speeds greatly increased to enhance
production rate. Not only production rate of spinning machines increased but speeds
of it’s downstream processes also increased simultaneously which requires better
quality of yarn for smooth process and without any interruption to get the maximum
efficiency. Hence now it is most important to co-relate fibre properties with respect to
it’s consumer process competency. In this article we will discuss the different cotton
properties and it’s impact on spinning process and product quality in present
prospective and will try to minimize the impact of poor fibre properties on process or
product Quality through better Mixing plan selection.
Introduction : In a spinning mill control over cotton quality requires in three steps i.e.
as below : -
1. Approval of Cotton Bales : - It is very much important to purchase the right
quality cotton bales according to defined quality standards. As cotton is a natural
fibre & commercial commodity hence it’s availability, prices & quality varies
time to time based on supply & market demand, therefore it is very important to
select the require quality cotton bales at reasonable prices which should viable
for spinning industries. Approval of cotton bales should be very strict against
it’s standards otherwise this will result stock of huge quantity of off standard
bales.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 2
2. Grading of Cotton Bales : - After reaching cotton bales in mill, these should be
tested & properly graded according to mill standards. If possible it should be
stack in warehouse grade wise.
3. Mixing Planning : - According to grade wise cotton bales stock and spinning
count pattern cotton bales to be selected for mixing plan with minimum possible
variation.
Major Critical Cotton Fibre Properties : - Followings are most common cotton
properties which measures at the time of selection of cotton bales :
1. Length : - Measured either in inches or in mm.
2. fineness : - Cotton fibre fineness usually measured in micronaire i.e. Weigh of
fibres in microgram per inch.
3. Strength : - Measured as fibre bundle breaking force in Gms per tex.
4. Maturity : - Measured either in term of Maturity coefficient or in Maturity ratio.
5. Uniformity : - Measured either in % or as an index.
6. Short Fibre Content : - Measured as %.
7. Trash Content : - Measured as %.
8. Moisture Content : - Measured as %.
9. Brightness : - Represents as Rd value against degree of reflection.
10. Yellowness : - Represents as + b value.
11. Colour grade : - Colour grade is determined with conjunction of Rd & + b
value.
All in one single value SCI.
Spinning Consistency Index (SCI) : - SCI is a calculated value based on a regression
equation. This equation takes into account all HVI properties and calculates one value
to be used on each sample tested. The SCI is an index derived with data from a large
number of cotton samples having a wide range in properties that is related to test data
from yarn spun from each sample. By multiple regression analysis the contribution of
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 3
each fibre property to yarn properties is revealed. Consequently a single SCI value is
influenced by inherent relationships of cotton micronaire, length, uniformity, strength,
Rd and +b.
The following are SCI equation for the most important HVI measurements including
colour : -
For HVI Calibration Mode :
SCI = - 414.67 + (2.9 x Strength) – (9.32 x Mic.) + (49.17 x Length in inch) + (4.74
x Uniformity Index) + (0.65 x Rd) + (0.36 x +b)
If no colour module is installed then SCI equation are as follows : -
SCI = - 322.98 + (2.89 x Strength) – (9.02 x Mic.) + (43.53 x Length) + (4.29 x
Uniformity Index)
For ICC Calibration Mode :
SCI = - 414.67 + (2.9 x Strength) – (9.32 x Mic.) + (49.17 x Length) + (8.61 x
Uniformity Ratio) + (0.65 x Rd) + (0.36 x +b)
If no colour module is installed then SCI equation are as follows : -
SCI = - 322.98 + (2.89 x Strength) – (9.02 x Mic.) + (43.53 x Length) + (7.79 x
Uniformity Ratio)
Effect of fibre properties on spinning process & Yarn Quality :- Each cotton
characteristic impose their own influence on spinning process & at ultimate yarn
Quality explained as below : -
Fibre Length : - Fibre length is the most important factor for spinning. Selection of
cotton fibre is usually based on fibre length only and it is also main deciding factor for
count range to be spun. Hence this impacts each & every process of spinning
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 4
operation. Following are the main influencing area’s where fibre length impact on
spinning performance & Yarn Quality :
Count pattern and spinning production rate : - Fibre length is main deciding
factor for count patter in spinning mill. Production speeds of spinning
machineries also very much depends on fibre length of cotton. In modern high
production spinning set up cotton fibre length can’t be selected as per old
traditional systems. For modern high production spinning set up cotton fibre
properties requires as below : - Table : 1 : Cotton fibre Properties requires for modern high production spinning set up
(Tested on HVI calibration Mode) Count Range
(Ne) Fibre Length
(mm) Micronaire Strength
(G/Tex) Maturity Index
Karded Yarn
Below 20sNe 26 to 27 mm 4.0 to 4.6 24 to 27 0.85
Combed & Karded Yarn
20s to 32s 28 to 30 mm 3.6 to 4.2 27 to 30 0.84 33s to 45s 30 to 32 mm 3.5 to 3.8 29 to 31 0.84 46s to 60s 32 to 34 mm 3.3 to 3.6 30 to 32 0.84
Definition : Modern High production spinning set up : - Spinning set up running with more than 50 kg. / Hrs
carding production rate, getting 40s Converted GPSS above 110 with a HOK level of below 12 in spinning,
equipped with modern autoconer.
Working performance : - Higher length variation causes poor working
performance of spinning processes, which lead lower production & huge
disturbance in process. Only achieving average fibre properties as per standard
is not guarantee for better spinning performance; hence it should be ensured that
each cotton lot should have minimum length variation. Cotton Lot’s having
higher variation should run in control quantity which given in next chapter i.e.
Mixing Plan.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 5
Higher Irregularity or unevenness : - If cotton length not suit to spin plan or
have higher length variation, e.g. to produce the 30sNE count if cotton selected
below 28 mm length, it will lead high irregularity or unevenness in yarn and will
also causes higher autoconer cuts and fabric defects.
High Hairiness : - Cotton selected of lower fibre length will causes high yarn
hairiness, that lead high fluff generation in department, more tendency of
traveller loading, excessive EYC cuts & cops rejection at autoconer and pilling
or barre problem in fabric.
Fineness / Micronaire of fibre : - The second most important factor for a spinning
mills to decide the count pattern is fineness of cotton fibre that is commonly known
as micronaire. Same as fibe length, it is also deciding factor for cotton selection &
spin plan of a spinning mill.
No of Fibres in Yarn Cross section : - Spinning of a particular fineness of
yarn is based on the fibre length of cotton & it’s fineness which decide how
many fibres will be in the cross section of yarn. It’s seems that below 90 No.
of fibres in cross section of ring spun yarn (for coarse & medium count range)
lead major working problem at spinning with lower yarn strength while no. of
fibres more than 300 in cross section of yarn lead higher unevenness in ring
spun yarn. Hence it is recommended to use right micronaire value for a
particular spin plan. Table : 1 Recommends guideline for micronaire value for
different count range.
Higher Neps Generation : - Low micronaire value causes high neps
generation in blow room & carding, which lead higher neps & imperfection
in final yarn and white spots or dots in dyed fabric. Low fineness cotton
fibres always have tendency to form fibre entanglement or neps, hence it is
recommended to reduce blow room beaters speed and carding production rate
whenever low micronaire value cotton being processed.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 6
Barre or shade variation : - Too much variation in micronaire value lead
barre problem or shade variation in fabric.
Genetic character : - Micronaire value of any cotton fibre strongly exhibits
it’s origin variety genetic character. If a cotton fibre fineness value does not
belongs to normal distribution of it’s origin variety, means either this fibre is
immature or it’s not belong to said variety. This type of cotton lot should be
avoided. Table -2 shows a general trend for critical cotton characteristics for
most common Indian cotton varieties. Table – 2 : General Cotton Properties of Major Indian varieties.
(Measured by HVI testing system by using HVI Calibration Mode)
Cotton Variety Major Producing States Fibre Length (mm)
Micronaire Strength (G/Tex)
Y 1 Maharashtra 22 to 25 4.5 to 6.0 18 to 24
V - 797 Gujrat 23 to 26 4.5 to 5.8 18 to 24
J - 34 Haryana / Rajasthan 26 to 29 3.8 to 4.6 24 to 28
J – 34 /F - 414 Punjab 26 to 30 3.8 to 4.6 25 to 30
H - 4 Madhya Pradesh 27 to 30 3.6 to 4.2 25 to 30
Shankar - 4 / 6 Gujrat 28 to 30 3.6 to 4.4 25 to 30
MECH - 1 Maharashtra 28 to 31 3.5 to 4.2 26 to 31
Bunny Brahma Maharashtra / Andhra 30 to 32 3.4 to 4.0 26 to 32
MCU - 5 Maharashtra / Andhra 31 to 33 3.3 to 3.8 26 to 32
DCH - 32 M. P. / Karnataka 32 to 36 2.8 to 3.2 30 to 34 Note : - Above data represents a general trend of variety followed 2 sigma limits of normal distribution.
Fibre strength : - Fibre strength is important factor for working of spinning
process and yarn strength. Fibre strength is directly proportionate to yarn strength
and working performance of spinning machines. However it seems that strength of
fibre is also related with others cotton properties like fibre length, micronaire &
maturity. Fibre bundle strength is a deciding factor for spinning machine speeds. If
fibre is not adequate stronger, then there have to compromise with production rate
and force to reduce speed of machines. Similarly ultimate yarn strength will be less
as require.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 7
Maturity : - Maturity of cotton fibre is related with it’s growing process. A fully
mature fibre means fibre achieve their complete growth process and developed in
all respects. Mature fibres achieve & exhibit better fibre properties in all respect as
per their origin of variety characteristics, as describe in Table – 2. Fibres which not
grown in a normal condition or picked up before there complete growth will fail to
belong their specific characteristics and will be shorter, weak & fine as compared
to mature fibres.
In HVI testing the maturity index is a relative value that is calculated by using a
sophisticated algorithm including other HVI measurements, such as micronaire,
strength & elongation. It indicates the degree of cell wall thickness within a cotton
sample. Table – 3 shows Avg. test results of total 98241 No. of bales w.r.t. degree of
maturity index. Table – 3 : HVI Test Results of MECH - 1 Cotton Showing Avg. Critical fibre properties
w.r.t. different degree of Maturity Index
(Measured by HVI testing system by using HVI Calibration Mode) Total No. of Bale
SCI Maturity
Index Micronaire UHML SFC% UI Stg
100 76 0.82 2.70 25.8 12.9 76.3 17.5
800 122 0.83 3.20 28.3 8.8 81.0 25.4
9412 128 0.84 3.59 29.5 8.4 81.9 26.6
24777 134 0.85 3.82 30.0 8.1 82.7 27.7
47870 140 0.86 4.06 30.6 7.7 83.4 28.7
13482 141 0.87 4.24 30.8 7.4 83.6 29.4
1800 143 0.88 4.49 31.4 7.2 83.5 30.6
Total observations = 98241 Bales.
Cotton Yarn : Quality Depends on Mixing Strategy
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.
Fig – 1 : Graphical representation of Fibre Length & Strength w.r.t. Maturity Index.
Fig – 2 : Graphical representation of Micronaire & SFC % w.r.t. Maturity Index.
Hence maturity is a key parameter for cotton selection & spinning process.
various testing methods it is represented as maturity coefficient, Maturity index or
as maturity ratio. Higher the numerical value means higher will be maturity of
fibres. Low maturity value impact at spinning process or yarn Quality as below :
25.8
28.3
17.5
25.4
16.017.018.019.020.021.022.023.024.025.026.027.028.029.030.031.032.033.034.0
0.82 0.83
0.820.83
0.84
2.70 3.20 3.59
12.9
8.8
Micronaire SFC %
arn : Quality Depends on Mixing Strategy
Vol. 124, No.-6, March 2014 Edition
Graphical representation of Fibre Length & Strength w.r.t. Maturity Index.
Graphical representation of Micronaire & SFC % w.r.t. Maturity Index.
is a key parameter for cotton selection & spinning process.
various testing methods it is represented as maturity coefficient, Maturity index or
as maturity ratio. Higher the numerical value means higher will be maturity of
fibres. Low maturity value impact at spinning process or yarn Quality as below :
29.530.0 30.6 30.8
25.426.6
27.728.7
29.4
0.84 0.85 0.86 0.87
UHML (mm)
Strength (G/Tex)
0.840.85
0.860.87
3.59 3.824.06
4.24
8.48.1
7.77.4
arn : Quality Depends on Mixing Strategy 2014
Page 8
Graphical representation of Fibre Length & Strength w.r.t. Maturity Index.
Graphical representation of Micronaire & SFC % w.r.t. Maturity Index.
is a key parameter for cotton selection & spinning process. In
various testing methods it is represented as maturity coefficient, Maturity index or
as maturity ratio. Higher the numerical value means higher will be maturity of
fibres. Low maturity value impact at spinning process or yarn Quality as below : -
31.4
29.430.6
0.88
UHML (mm)
Strength (G/Tex)
0.88
4.49
7.2
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 9
Fibre rupture : - Immature fibres breaks into multiple pieces in blowroom &
carding section during metallic action of beaters and carding wires causes increase
in short fibres & microdust which further reduce the effective length of fibre &
strength. This fibre rupture increases yarn breaks, yarn defects, spinning waste &
yarn imperfection level subsequently reduces working efficiency of spinning
machineries causing lower production, yarn recovery with lower yarn strength.
Dead cotton Neps : - Immature fibres create heavy neps during spinning process
which ultimately reflect as white dots in dyed fabric and causing fabric rejection.
Table – 3 & Fig. – 1 showing that fibre maturity is directly proportionate to fibre
length & bundle length of fibres.
Uniformity : - Settings of spinning drafting rollers depends on the length of fibres.
To obtain optimize & correct spinning draft roller settings fibre uniformity is very
important factor. Cotton fibre with low uniformity causes very high variation in
process and creates difficulties for spinners to set the right setting for particular
cotton mixing.
Short fibre content : - Fibre length below half inch i.e. below 12.5 mm consider as
short fibres. High short fibre % in cotton lead many problems in spinning process
such as high end breaks, excessive yarn defects, very high fluff generation, lower
machine efficiency, lower yarn realization and higher worker turn over.
Trash Content : - High trash content in mixing causes higher waste extraction,
high end breaks rate at ring frame & higher yarn imperfection & classimat faults.
It’s also appearing as black dots in greige fabric usually known as kitti particles.
Moisture Content : - Cotton is a hygroscopic fibre, it’s absorb moisture from a
high humid atmosphere and evaporate when store in dry atmosphere. For smooth
spinning operation cotton fibre should have moisture in range of 6 to 8 %. Moisture
content below this limit causes high fluff generation & higher end breaks, while
cotton having high moisture content difficult to open & clean in blow room -
carding, hence creating very high imperfection and yarn slubs which again causing
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 10
end downs at ring frame stage and lowering the production efficiency with increase
in yarn imperfection & defects.
Colour Grade : - Variation in Colour grade is major responsible factor for shade
variation in cotton yarn & fabric.
Grading of Cotton Bales
It is very difficult to grade a cotton Lot base on all 11 parameters as mentioned
above, hence we can decide four major critical parameters for grading of cotton
bales which represent the overall grading of cotton. These parameters may be
utilized for cotton bales procurements, stacking and finally for selecting the cotton
bales for Mixing Plan. If a mill cotton purchasing is strictly from a particular region
then there will be less chances of too much variation in colour grade, hence critical
parameters for them might be as below : -
1. Fibre Length : - Must require to decide the count pattern of spin plan.
2. Micronaire : - Must require to decide the count pattern of spin plan.
3. Maturity : - Requires to control the quality of cotton, it’s also represent to
fibre strength.
4. Short fibre % : - Requires to control the working performance of spinning
mill and yarn realization. it’s also represent to uniformity of cotton. Less the
SFC more the uniformity of fibre.
If cotton procurement of mill is from different - different region, then there
might be possibility of variation in cotton colour grade. Hence in that case colour
grade also to be taken into consideration.
Table -4 : Grading of Medium Long staple Cotton Lot's based on Critical Parameters
(Measured by HVI testing system by using HVI Calibration Mode)
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 11
Grade Fibre Length
(mm) Micronaire
Maturity Index
SFC % Stock %
A + + > 31 3.5 - 4.2 > 0.85 < 7.5 13
A + 30 - 31 3.5 - 4.3 > 0.85 < 8.0 30
A 29 to 30 3.6 to 4.3 > 0.85 < 9.0 35
B 28 to 29 3.6 to 4.3 > 0.84 > 9.0 20
C Out of above Range 2
Stock % based on assumption only for explanation purpose.
Mixing Planning
Object : To Mix cotton fibres of different bales in a homogeneous form to overcome
the variations of cotton properties and maintain the uniformity & consistency in
throughout spinning process and in yarn Quality.
Making a mixing plan may be a tedious job, but spinning performance is totally
depends on it. Hence investing time and skill on mixing plan will pay consistency
in spinning w.r.t. working & quality as a result. A practical mixing plan may be
prepared as below : -
1. First check the availability of grade wise cotton bales and spin plan.
2. Then select grade wise No. of cotton bales in ratio of present cotton bales
stock and as require for spin plan. Stock of cotton bales to be utilized in such
a manner that long staple cotton (i.e. A + + in Table – 4) to be used for fine
count pattern.
3. If present spin plan is not support to fine count range then it should be
preserved for future, if there are possibility in future.
4. To control the length variation in a selected mixing plan either we have to
consume “A++” grade cotton first or we have to preserve it till all the bales of
“B” grade cotton exhausted.
5. Refer to cotton grading system as per Table – 4, in a mixing plan either there
should be top three grade bales (i.e. A ++, A + & A Grade) to be used or
lower three grade bales (i.e. A+, A & B Grade) to be used.
6. In a mixing plan fibre length range should not exceed more than 2.5 mm and
Micronaire range to be maintained below 0.60. Refer Table – 6.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 12
7. Low variation in fibre length require to set right the correct gauges of
spinning drafting rollers and to avoid the fibre rupture and drafting waves.
Variation in fibre length causes poor Quality & working of spinning along
with high fly generation.
8. Low micronaire range must require maintaining the uniform no. of fibres in
cross section of yarn, which ensure better yarn evenness & single yarn
strength.
9. No of cotton lot’s in a mixing plan to be selected in such a manner that
participation of each cotton lot bales should not be more than 5 %. For
example if we are making a mixing plan for 100 no. of bales than there
should be at least 20 No. of Cotton lot’s contributing 5 bales each for each
batch. This is require to avoid wide changes in mixing plan, even if there is
change of one single cotton lot then there will be only 5 % change in
particular mixing plan.
10. Replacement of cotton lot should be in decreasing and increasing order. If
one cotton lot going to exhaust in mixing that should be run out slowly and
replacement lot to be inserted in same way, which ensures minimum variation
in process during replacement of cotton lot’s. Table – 5, shows how one cotton
lot should run out and another should replace it. Table – 5 : Showing Replacement process of cotton Lot in Mixing.
Decreasing Order Increasing Order
Cotton Lot going to exhaust in Mixing Cotton Lot started in Mixing
Date Lot No.
Opening Stock of Bales
No. of Bales issued
Closing Stock Lot
No.
Opening Stock of Bales
No. of Bales issued
Closing Stock
10/09/2013 105 15 5 10
11/09/2013 105 10 4 6 251 100 1 99
12/09/2013 105 6 3 3 251 99 2 97
13/09/2013 105 3 2 1 251 97 3 94
14/09/2013 105 1 1 0 251 94 4 90
15/09/2013 251 90 5 85
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 13
11. This system ensures very little change in mixing on day to day basis. Only
one bale replacement out of 100 bales mixing will be only 1 % change in
mixing plan that is almost negligible.
12. To further minimize the variation during Lot change it should also be
taken care that same grade cotton or cotton lot with same characteristics to be
replaced.
13. If cotton procured from different – different station, then try to replace the
cotton lot with same origin or station. Table – 6 : Acceptable range for Daily Mixing plan.
Parameters Ideal Range Maximum acceptable Range
Fibre Length (mm) 2.0 2.5 Micronaire 0.6 0.8 Rd 5 6 + b 2.0 2.5
Monitoring of colour Grade : - Monitoring of colour grade is also a very
important job to control the shade variation or barre problem in resultant yarn &
fabric. Following guidelines might be useful for better control on colour grade
of cotton : -
Rd value : - Usually in Indian cotton Rd values lying in between 72 to 82. For
better control it is advisable to maintain the Rd value range below 5 in daily
Mixing plan. Refer Table – 6.
+ b : - + b value significantly differ region wise and variety wise. Indian cotton
usually lying + b value in range of 6.0 to 11.0. It is better to maintain the + b
range below 2.5 in one variety cotton mixing. Refer Table – 6.
Colour Grade : - The colour grade is determined by locating the quadrant of the
color chart in which the Rd and +b values intersect. For example, a sample with
Rd value of 72 and +b value of 9.0 would have a color code of 41-3. Colour
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 14
grade is represented in three digits as xx-y. First digit represent to brightness of
cotton. Lower the number higher will be brightness of cotton. Second digit
represents to yellowness of cotton, yellowness increases with increase in second
digit number. There are 25 colour grades and five categories of colour grades.
Indian cotton usually lying in white & light spotted categories with Middling to
good middling colour grade.
To avoid the shade variation or barre problem it is advisable that only four
adjacent cotton grade should select for mixing plan, e.g. 11, 12, 21, 22 may run
together but running 11 with 31 or 11 with 13 should be avoided.
Colour grade categories of spotted, tinged & yellow stained i.e. represented by
3, 4 & 5 number in second digit of colour grade should be strictly avoided.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 15
Chart – 1 : USDA Colour grade chart for cotton short /medium cotton.
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 16
Table – 7 : Categories & Colour Grade for Cotton
Category Color Grades Symbols Code #
White Good Middling GM 11
Strict Middling SM 21
Middling Mid 31
Strict Low Middling SLM 41
Low Middling LM 51
Strict Good Ordinary SGO 61
Good Ordinary GO 71
Light Spotted Good Middling GM LtSp 12
Strict Middling SM LtSp 22
Middling Mid LtSp 32
Strict Low Middling SLM LtSp 42
Low Middling LM LtSp 52
Strict Good Ordinary SGO LtSp 62
Spotted Good Middling GM Sp 13
Strict Middling SM Sp 23
Middling Mid Sp 33
Strict Low Middling SLM Sp 43
Low Middling LM Sp 53
Strict Good Ordinary SGO Sp 63
Tinged Strict Middling SM Tg 24
Middling Mid Tg 34
Strict Low Middling SLM Tg 44
Low Middling LM Tg 54
Yellow Stained Strict Middling SM YS 25
Middling Mid YS 35
Use of off standards bales : - In spinning mills there should be strict control on
purchasing of cotton bales or passing for Quality specification, otherwise there
might be lot of off standard cotton bales accumulate in mill godown which will
never allow spinner to prepare a control mixing plan. However even after better
control there might be chances of some off standard cotton bales which do not
belongs to normal standard either for any single parameter or due to fail of multiple
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 17
parameters. These bales to be utilized in very control manner so it’s bad quality
should not affect spinning process and yarn produced. Based on quality parameters
of off standard bales these may be consumed in control manner (i.e. in a range of 1
to 5% according to quality parameter) as below : -
1. If there is only slight variation in any one or two parameter from standard
then such cotton bales may be considered in mixing with 3 % contribution.
For example if standard for fibre length is above 29 mm & Micronaire is
above 3.6 and actual value of a cotton Lot found 28.5 mm & 3.5 Mic value
then such cotton bales may be considered with 3 % ratio in mixing.
2. If there is significant deviation in a single value such as instead of 29 mm
fibre length observed 27 mm while rest other parameters observed within
range in that case such cotton bales may be consumed with below 2 % ratio.
3. If 2 -3 parameters fail to meet the standard specs then such cotton bales
should be strictly consumed with below 1 % ratio.
Mixing Plan monitored through Spinning Consistency Index : - Instead of
monitoring of several parameter for a mixing plan, it might be more easy to
monitor the “SCI” value of cotton properties obtained from HVI test report.
Following guidelines may be adapted for using “SCI” value in cotton grading &
mixing planning : -
1. Cotton may be graded in five grades & store in warehouse according to their
SCI value i.e. as below : - Table – 8 : Possible Grading system according to Spinning Consistency Index (SCI) (Measured by HVI testing system at HVI calibration mode with Colour Grade Module)
Grade
Spinning Consistency Index (SCI) Value Range
A + + Above 150
A + 140 to 149
A 130 to 140
B 120 to 129
C Below 120
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 18
2. According to stock position a mixing plan to be prepared and Average,
Minimum, Maximum and range should be drawn for SCI value.
3. Average SCI value of daily mixing should be maintain constant and there
should not be more than +/- 2 deviations on daily basis.
4. It should be trying that maximum & minimum range of SCI value should not
be more than 30, for an ideal mixing plan it should be maintain below 20.
5. The total range of maximum & minimum SCI value should also be monitor
on daily basis and there should not be too much variation on daily basis.
Conclusion : - Cotton is most favorable fibre for spinning industries. As cotton is a
natural fibre, hence variation in it’s properties is also an inherent characteristic. To
overcome these variations scientific & systematic control requires on cotton Quality.
Control over cotton quality in a spinning mill recommends in three stages i.e.
Approval of cotton bales, Grading of cotton bales & finally selection of cotton bales
for Mixing plan. Major Cotton fibre properties and it’s impacts on spinning
processes & yarn Quality explained in details with examples, data & graphical
representations. More emphasis has been given on SCI & Maturity of fibres.
Maturity of cotton fibre is an important parameter and also impact on others
parameters such as length, strength, elongation etc. All in one single value derived
from regression equation Spinning consistency index (SCI) is a value influenced by
inherent relationships of cotton micronaire, length, uniformity, strength, Rd and +b,
may helps spinners to monitor only one parameter for decision making.
Mixing planning is a very important function for spinning operation and
investing the time & skill for systematic mixing plan pay return as consistency in
productivity & Quality. A systematic mixing plan by maintaining the lowest possible
variation in cotton quality parameters ensures trouble free yarn production with
consistent yarn Quality. Variation in cotton colour grade is major responsible factor
for shade variation and barre problem in fabric, hence control over cotton colour
Cotton Yarn : Quality Depends on Mixing Strategy 2014
By Mr. Sunil Kumar Sharma Published in The Indian Textile Journal, Vol. 124, No.-6, March 2014 Edition Page 19
grade is most important function of mixing plan, it can’t ignore. Consuming the off
standard Quality bales are a tricky job and it should be used in very control manner
so performance of spinning process & yarn quality should not affect.
References : - Uster HVI 1000 Application Handbook.
Cotton Council International – 2008 Buyer Guide.
USDA – Cotton Classification.
Produced by : Mr. Sunil Kumar Sharma,
Dy. General Manager (QAD, PPC & Customer Care)
Mobile No. : – 09552596742, 09921417107
E_mail : - [email protected] Loknayak Jayprakash Narayan Shetkari Sahakari Soot Girni Ltd.
Kamalnagar, Untawad – Hol, Shahada,
Tal. : - Shahada, Dist. : - Nandurbar (MS)
Pin : - 425409