MILANGE YARNS
Introduction:
History of yarn manufacturing draws our attention to the earliest days
of the 19th century, when practically this was made possible by Ring Spinning. After
this many developments have been made in terms
of technology and improved process techniques have been adopted for the most
efficient and convenient method of yarn manufacturing. So, what in fact the
yarn is? “Yarn is a long continuous length of interlocked fibers, which may
be used in various applications depending upon the intended end use.”
There may be variety of yarns depending upon the manufacturing process
for instance spun yarn, twist less yarn, fancy yarn, slub yarn, mélange yarn
(Dyed yarn) and so on. The below given chart classifies the yarn more
systematically.
Fig. Different Types of Yarn
Indians were the pioneers in making the mélange yarn for the first
time in 1980’s. It may be defined as “the yarn produced by the combination of
at least two or more than two fibers”. Conventionally, the term mélange is used
for such yarns which are produced by the combination of two fibers (whether of
same type but different in color or type of fiber used is different). Further
more, Mélange yarn can be classified into two of its very basic types:
I.
Blended mélange
yarn
II. Non‐blended mélange yarn
I. Blended Mélange Yarn:
Such type of yarn in which different
fibers are mixed/blended together in a certain fixed ratio for instance PC
(Polyester Cotton blend) 50:50, PC 70:30, PV 80:20, CVC 40:60 etc.
II.
Non‐Blended
Mélange Yarn:
Yarn in which there are no different
fibers blended together, but different colored fibers of same type are used to
make the yarn e.g. 100% cotton dyed yarn, 100% bamboo yarn etc.
MANUFACTURING PROCESS:
I.
Preliminaries
Of The Process:
The production of mélange yarn is similar to the simple (Un‐dyed)
yarn, but there are some additional things that need to be discussed here.
Initially, the raw cotton is stored in form of bales in godowns. These bales
after certain time of conditioning are sent to different processing mills for
dyeing. There the bales are opened to flock form and conventionally, disperse
dyes, reactive dyes and VAT dyes are used for fiber dyeing. After this is done,
the bales are returned to the mill; these bales are again opened, well mixed,
conditioned and pressed together in form bales but with a (LOT NUMBER).
This number may vary from mill to mill for identification purpose, but this is
important to discuss because we are not sure that we get the same type of dyed
fibers ( in terms of dye ability, dye affinity, rubbing & washing fastness
) of the fibers every time. This may depend upon the dyeing conditions, dye
quality, recipe, process conditions, fiber used (mature/ immature/ dead fiber content).
These factors are important to consider because these are some unrevealed
factors that causes very common problems in mélange yarn i.e. rejection of the
shade. There comes the importance of making the LOTS, so that we can easily
track from where the error occurs.
This identification leads us to proper issue of bales for particular
order in order to avoid the shade variations. However, another technique may be
used which is termed as “SAMPLING”. For every new LOT or new mixing of
the running order, a sample should be made and get it cross‐checked with the
Customer’s sample. In this way we can
reduce the chances of error and shade variation can be limited and predicted in
advance, so necessary remedies can be taken.
II.
Types Of
Blends:
Normally, we speak of types of blends depending upon the percentage of
shade (colored fibers) in the mixing recipe or yarn. So, this classification
mainly depends upon the Shade percentage, but it can also be done deliberately
to ease and balance the process.
a) Blow room Blend
b) Drawing Blend
a)
Blow room Blend
Shade:
Such shades which are blended through blow room are called “Blow
Room blends”. Normally, darker shades and shades constituents variety of
colored fibers are run as blow room blend shades. Conventionally, shades having
percentage more than 15% are run as blow room blends. This is done to achieve
the maximum blending and uniformity in the shade.
It should be clear that by the term “shade” here we only mean the
total percentage of colored fibers in the yarn. For example let us consider a
shade SC‐30 (this code may vary from mill to mill), it has fiber coding
as:
Sulfur Black‐01
|
=
|
27.5%
|
Green‐09
|
=
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3.00%
|
White
cotton
|
=
|
69.5%
|
So, in above recipe shade SC‐30, total percentage regarded as
shade is 30.5%.
b)
Drawing Blend
Shade:
Such shades which are blended on draw frame in form of alteration in
doublings are termed as “Drawing Blends”. Mostly, lighter shades are
blended on draw frame, as they are easy to blend and provide ease in
balancing the process. In drawing blends, we can blend having 15% shades.
III.
Calculating
the Drawing Blend Shades:
Usually, drawing blends are set in accordance with the need to make
the process easy and some how on shade percentage. This can be made clearer by
considering the example below. Let us consider the shade SGL‐915 (these
codes not holds for all mills) having following recipe:
Olive – 01
|
=
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2%
|
White Cotton
|
=
|
98%
|
This is the
required percentage of shade in the yarn, but this recipe will vary if we make
it drawing blend. Now, this depends upon us, whether in what percentage we need
to blend that and adjust the doublings on the draw frame in accordance with
that. This can be easily under stood by following calculations. Let us say, we
want to run it as 2 carded sliver cans of this Blow room blend shade, and 6
carded sliver cans of the cotton. So the actual recipe will shift in this way,
and that recipe is to be made and mixed in blow room.
Mixing cans of carded sliver
|
=
|
02
|
White
cotton cans of carded sliver
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=
|
06
|
Total doublings
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=
|
08 (on one side of draw
frame)
|
This gives us the blow room recipe as follows:
|
|
|
Olive –
01
|
=
|
8%
|
White
cotton
|
=
|
92%
|
But the question is
how was it done?? There is a simple logic behind that, so let us calculate it.
Say, we are running 65 grains / yard of the sliver on draw frame.
We have, 02 slivers of mixing
|
=
|
65 * 2
|
=
|
130
grains / yard
|
White cotton 06
slivers
|
=
|
65 * 6
|
=
|
390 grains / yard
|
Total (grains/yard)
|
|
|
=
|
520 grains / yard
|
By determining the simple percentage, we have:
Shade %
|
=
|
130/520
|
* 8% =
|
2%
|
White cotton
|
=
|
390/520
|
* 92% =
|
98%
|
This 8% was
blow room recipe, and 6% additional
of olive – 01 fiber was added, which is reduced here on draw frame and
ultimately brought to the 2% which was the required shade in the yarn.
This may be done depending upon the requirement and easing the process, as
drawing blend shades are easy
to run as compared
to blow room blends. There is only one set back, that they require an extra
passage of drawing for proper blending of shade and attaining uniformity ,
which some how effects the sliver quality and adds cost to extra machinery.
IV. Common Problems In Making Mélange Yarn:
There may be lot of problems occurring in the production process, but
we will only highlight such problems which are in particular related to the
mélange yarn. Any of these problem may cause the rejection of production made,
ultimately suffering a major loss. So, in order to get rid of this, we need to
consider some of very basic flaws & focus upon its remedies. These problems
are:
a) Shade variation
b) Variation in ratio (esp. in PC/PV/CVC) yarns
c) Spots in the fabric
a)
Shade
variation:
When ever there is
the difference between the colors of two “LOTS” of the same running order, this
is termed as “Shade Variation”. There will be difference in the color of
the yarn / knitted fabric on the whole, which should be removed in order to
avoid rejection of LOT.
There is variety of
reasons of this variation as far as my knowledge is concerned. Some of them are
listed below:
•
Twist
variation in the yarn over ring frame (T.M / T.P.I variation)
•
Wrong fiber
blended / proportion of fiber is not exactly the same
•
Moisture
content of the yarn
•
Count
variation
•
Dyed fiber
•
Twist
Variation:
There is difference
observed in the shade while the same shades are being run on two frames but
with different T.P.I. it reflects like greater the T.P.I will give the darker
shade as compared to the lower T.P.I. T.P.I checking tests should be followed
strictly to avoid this sort of problem. A clear example is stated below for
clarification.
SGD – 1616 (30/1 Knitting, Non‐Compact)
|
SGD – 1616 (30/1 knitting, Non‐
compact)
|
T.M = 3.75
|
T.M = 3.92
|
Fig. Difference in shade due to T.P.I
•
Wrong Fiber
Blended (Improper Mixing)
The other and very
major flaw that is observed is use of improper fiber/ improper ratio of any
fiber leads to change in “TONE” and “DEPTH” of the knitted
fabric. The following graph shows the percentage contributions to shade
variations. So, the proper selection and exact ratio is very basic requirement
in order to avoid this major flaw. In order to make this concept clearer, we
should be well defined about the two above cited words.
Fig. showing percentage of different causes of shade variation of a
mil
We find variety of black colored fiber which is used conventionally in
the industry. For example, we consider the series of black dyed fibers.
Sr.
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Fiber Code
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Fiber Tone
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|
No.
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||
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|
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1.
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Reactive
black – 01
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(Slight Red)
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|
|
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||
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2.
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Reactive
black – 02
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(Green)
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|
|
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||
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3.
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Reactive
black – 03
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(Reddish)
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|
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||
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4.
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Reactive
black – 05
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(Blue)
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||
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5.
|
Reactive
black – 09
|
(Purple)
|
|
|
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||
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|
|
Fig. fibers with their tones
From above chart, we conclude that for same black fibers, we find
difference in their tones (clearly visible when exposed to sunlight). So, using
the wrong fiber/ fiber in wrong proportion leads to variation in the tone of
the yarn/ fabric. There is calculation, with which we can alter the tones and
play with shade percentages, which are discussed below.
Now, come to the depth of the shade. Depth can be defined as “the
darkness or brightness of shade”. Whenever there occurs the problem of shade,
first check whether the tone is varying or not?? There comes the depth, whether
it is lighter or darker.
Consider example of shade SCD – 502
with following recipe:
Chocolate – 04
|
=
|
4.5%
|
Chocolate – 01
|
=
|
18.5%
|
Brown – 07
|
=
|
44%
|
Yellow – 02
|
=
|
1.75%
|
White cotton
|
=
|
31.25%
|
This gives us the final shade in this color
the change in
proportion of different fibers used is noticeable, then tone of the shade will
vary from the desired tone. So, we have some calculations with the help of
which we can get its desired tone. This is known as “Mixing Conversion”.
Now, let us see, how it is done??
Sr.
|
Fiber
code
|
Original
|
Rejected
|
New
|
Difference
|
|
No.
|
Recipe
|
Recipe
|
Values
|
|
||
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||||
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|
1.
|
Chocolate ‐ 01
|
18.5
|
18
|
21
|
2
|
|
|
|
|
|
|
|
|
2.
|
Chocolate ‐ 04
|
4.5
|
4.5
|
5.24
|
0.74
|
|
|
|
|
|
|
|
|
3.
|
Brown ‐ 07
|
44
|
42
|
49
|
7
|
|
|
|
|
|
|
|
|
4.
|
Yellow ‐ 02
|
1.75
|
1.5
|
1.749
|
Approximately 0
|
|
|
|
|
|
|
|
|
5.
|
Cotton
|
31.25
|
34
|
39.66
|
5.66
|
|
|
|
|
|
|
|
|
In the rejected
recipe column, we have altered many fibers. This is done to clear the concept
and for better comprehension. But it should be noted that this can only be done
when you have excellent vision, no color blindness, good experience and
distinctive approach to differentiate the tones of the fibers. Coming back to
the point, from the rejected recipe, choose any one fiber whose percentage is
reduced from original recipe say yellow – 02, and follow the steps below:
1. Divide the original vale by
deviated value, these yields a constant.
1.75/1.5 = 1.1666 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ (i)
2.
Now multiply this constant vale (1.1666) with all the values of
rejected recipe one by one, and write the answers in the third column against
each of the value. E.g. 1.1666*18 = 21.00
3.
Now, subtract the rejected recipe from the new values and put the
answers in the next column (Difference) one by one against each value. E.g.
21‐18 = 2.this is done because we have already put this amount of fiber in
rejected mixing, that’s why we need to exclude that to convert it to the
original recipe.
4.
The amount stated in difference column is to be added to reject mixing
per 100 kg to get it converted to original recipe. If 2000 kg mixing is
spoiled, multiply it with the factor 20. (simple math)
5.
This will give us the original recipe and mixing will be converted,
but after this we need to manually/ by use of machines mix it thoroughly and
properly. This can be verified in following way.
6.
Sum up all the values of NEW VALUE column, and find percentage of each
fiber, which should be the same as the rejected recipe value. E.g. the sum is
116.65. so, the percentage is 21/116.65 *100 = 18.00
7.
So this was the way by which we can convert the mixing, but one thing
should be noted it depends upon the vision and experience.
•
Moisture
Content:
Cotton fibers are
hydrophilic in nature and absorb the moisture from atmosphere according to
their regain percentage. Due to this factor, we do condition the yarn in order
to impart the strength in the yarn and gain some weight. So, a type of shade
appears in the knitted fabric if it is made from the combination of the
conditioned and non‐conditioned yarn cones.
•
Count
Variation:
An internal type of
shade (visible when fabric is exposed to light in tilted condition) is observed
on the fabric if there is found a minute difference in count of the two
cross‐matched yarns. So, in order to avoid it, wrapping should be done
periodically to avoid the variations in sliver hanks, roving hank and the yarn
count.
•
Dyed Fiber:
One of the much
unconsidered factors is the fiber dyeing. We are not sure about the dye washing
and rubbing fastness, so due to this we suffer a lot of problems in production.
So, in order to tackle this problem, we need to conduct washing and rubbing
fastness tests of each fiber we use and should assign the “LOT NUMBERS”
as discussed earlier in this topic.
b)
Variation
in Ratio:
This error is
observed in Blended mélange yarn i.e. mostly in PC/PV/ Heather Grey yarn. This
can make the shade dark or lighter. This is because of the increase in
percentage of any of the constituents of the yarn. This can be avoided again by
periodic wrapping and sliver hank checking over the draw frames and the Speed
frames. Ratio can also be checked and verified whether the calculations done
are exact or not?
c)
Spots In
the Fabric:
This issue is
related to quality parameters of the fabric. It tells us about the final
quality of the fabric/ yarn. It should be kept in mind that there should not be
any of the white spots (neps) on the surface of dark shades. Similarly, there
should be no dark neps on lighter shades. So, raw material used should be
considered before to avoid such problems. For instance, any darker shade say
80% is shade and 20% is white cotton. So we should use combed sliver in mixing
recipe instead of cotton bales that may cause the neps in the final fabric.
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