How to determine the linear density of yarn by yarn count system

Specific Objectives:

In this article, we will understand the testing method to determine the cotton yarn count/ linear density using the English cotton yarn count system.

Fig: Yarn Count Measurement

Introduction:

Yarn count refers to a numerical number that indicates the thickness and diameter of a yarn. However, it is impossible to determine the yarn's diameter in any meaningful way. Therefore, to determine the fineness/count of a yarn, the weight of a specific length of yarn is determined, which gives an estimate of a yarn count by a numerical number. This quantity is known as the linear density of yarn.

There are two yarn numbering systems of linear density are used which are given as follows;

1. Direct yarn numbering system/ direct yarn count system
2. Indirect yarn numbering system/ indirect yarn count system

1. Direct Yarn Count System:

The direct yarn count system of linear density is based on measuring the weight per unit length (W/L) of a yarn. There are two main direct systems used for the measurement of filament yarn count, which are given as under;

Tex yarn count: In this yarn count system, the unit of weight is in grams and the unit of length is in 1000 meters.

Denier yarn count:  In this yarn count system, the unit of weight is in grams and the unit of length is in 9000 meters.

Note: In the direct yarn count system, the linear density of the coarse yarn is higher than the fine yarn. 

2. Indirect Yarn Count System:

The indirect yarn count system of linear density is based upon the length per unit weight (L/W) of yarn and is usually known as count because it is based on the number of hanks of a specific length which are needed to make up a fixed weight. This yarn count system is mainly used for the measurement of staple yarn count. The different indirect yarn count systems related to the different regions and the type of yarn manufactured are used which are given below;

English cotton count system (Nec): In this yarn count system the unit of length is hanks (840yards) and the unit of weight is 1 pound

Metric count system (Nm): In this yarn count system the unit of length is 1000 meters and the unit of weight is 1000 grams.

Woollen (Ny): In this yarn count system the unit of length is 256 yards and the unit of weight is 1 pound.

Worsted Count (Ne_w): In this yarn count system the unit of length is 560 yards and the unit of weight is 1 pound.

Note: In the indirect yarn count system, the Yarn number/Linear Density of the coarse yarn is lower than the fine yarn. 

Materials and Equipment:

The following instruments and materials are required for the measurement of yarn count.

• Electronic ring wrapping reel machine
• Yarn creel stand
• Cotton yarn package/Yarn bobbins
• Electronic Weighing balance
• Calculator

Procedure:

1. First of all, we will collect the yarn bobbins from the ring department of a textile spinning mill.
2. Then Yarn bobbin/package is placed in the creel section of the electronic ring wrapping reel. 
3. According to the standard, the yarn lea length should be 120 yards for correct evaluations of cotton yarn count otherwise the incorrect result is achieved.
4. A ring wrapping reel has a girth size of one yard, thus 120 revolutions are given to the ring wrapping reel to get 120 yards of cotton yarn lea.
5. At least 10 samples of yarn lea were taken from the ring wrapping reel machine.
6. Then put yarn lea one by one on a weighing balance and note the weight of each lea sample in grams.
7. Average results of 10 yarn lea samples are taken in this practical so that accurate results are achieved.
8. After finding out the average lea weight, the English cotton count of cotton yarn is calculated with the help of the following formula;
9. $\mathrm{English} \mathrm{Cotton} \mathrm{Count}=\frac{64.8}{\mathrm{yarn} \mathrm{lea} \mathrm{weight} \mathrm{in} \mathrm{gram}}$
10. Then the standard deviation (S.D) and coefficient of variation CV% of yarn lea samples are calculated by using the following formulae;

$\mathrm{S}.\mathrm{D}=\sqrt{\frac{\sum (\mathrm{X}-\overline{\mathrm{X}}}{\mathrm{n}-1}}$

$\mathrm{C}.\mathrm{V}\%=\frac{\mathrm{S}.\mathrm{D}}{\mathrm{Mean}}\times 100$

Application and Try Out:

After completing the above-mentioned test procedure, the obtained data is put in the following table for the calculation of English cotton count and coefficient of variation (CV %) of cotton yarn.

Table: Yarn count calculation:

Sr. #	Yarn Lea weight in gram	$\left(\mathrm{X}-\stackrel{-}{\mathrm{X}}\right)$	(${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$	$\mathrm{Yarn} \mathrm{Count}=\frac{64.8}{\mathrm{lea} \mathrm{weight} \mathrm{in} \mathrm{gm}}$
1	1.6	-0.03	0.00	40.50
2	1.8	0.17	0.03	36.00
3	1.6	-0.03	0.00	40.50
4	1.8	0.17	0.03	36.00
5	1.7	0.07	0.00	38.12
6	1.8	0.17	0.03	36.00
7	1.5	-0.13	0.02	43.20
8	1.6	-0.03	0.00	40.50
9	1.4	-0.23	0.05	46.29
10	1.5	-0.13	0.02	43.20
	Mean ($\stackrel{-}{\mathrm{X}}$)= 1.63		$\sum$ (${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$=0.18	Avg. Yarn Count = 40.03

Standard Deviation:

$\mathrm{S}.\mathrm{D}=\sqrt{\frac{\sum (\mathrm{X}-\overline{\mathrm{X}}}{\mathrm{n}-1}}$ 

(*Where n is the number of values/sample.)

$\mathrm{S}.\mathrm{D}=\sqrt{\frac{0.18}{10-1}}$

$\mathrm{S}.\mathrm{D}=\sqrt{\frac{0.18}{9}}$

$\mathrm{S}.\mathrm{D}=\sqrt{0.02}$

S.D = 0.1414

Coefficient of variation (CV %):

$\mathrm{C}.\mathrm{V}\%=\frac{\mathrm{S}.\mathrm{D}}{\mathrm{Mean}}\times 100$

$\mathrm{C}.\mathrm{V}=\frac{0.1414}{1.63}\times 100$

$\mathrm{C}.\mathrm{V}=0.087\%$

Results and discussion:

Cotton yarn count (Nec)          =          40 Nec

Standard Deviation (S.D)        =          0.1414

C.V% of yarn linear density    =          0.087 % 

Safety Precautions:

1. The length of yarn lea should be accurately measured.
2. Yarn lea length should be 120 yards.
3. The weight of yarn lea should be accurately measured.
4. The weighing balance must be calibrated.
5. The yarn count calculation should be accurate.

FAQs:

1. What are the objectives of the ring-spinning process in the textile Industry?
2. What is the girth size of an electronic ring-wrapping reel machine?
3. How many lengths of yarn lea sample is required to measure the yarn count?
4. How to calculate the linear density of cotton yarn?
5. What is the formula of yarn count by the English cotton count system?
6. How the (CV %) of yarn count is calculated?

Author:

Engr. Muhammad Usman Ashraf

HOD Textile Department at TEVTA Punjab, Pakistan.

M.Sc Textile Engineering (NTU, Faisalabad)

Email: usmanashraf884@gmail.com