MILANGE YARNS

                                                                    MILANGE YARNS

Introduction:

History of yarn manufacturing draws our attention to the earliest days of the 19^th 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	=	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	=	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	=	06
Total doublings	=	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.	Fiber Code	Fiber Tone
No.
1.	Reactive black – 01	(Slight Red)
2.	Reactive black – 02	(Green)
3.	Reactive black – 03	(Reddish)
4.	Reactive black – 05	(Blue)
5.	Reactive black – 09	(Purple)

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
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.