Quality Assurance Testing of a Textile Spinning Process

Textile Spinning is the process in which short fibres are converted into long lengths of yarn by twisting. In this process, the fibres have to pass through different departments during yarn formation, which is as follows;

Input	Departments of Spinning Process	Output
Cotton Bale	→     Blow room Department     →	Lap Sheet
Lap Sheet	→          Card Department          →	Carded Sliver
Carded Sliver	→       Drawing Department       →	Drawn Sliver
Drawn Sliver	→        Simplex Department       →	Roving
Roving	→          Ring Department          →	Yarn Bobbin
Yarn Bobbin	→     Auto cone Department     →	Yarn Cone

For the quality control & quality assurance testing in a textile yarn manufacturing unit, the end product of each department should be tested, so that the required quality of the yarn is obtained.

Specific Objective:

In this article, we will test the different quality parameters (e.g. grains/yard, hank roving and CV %) of the following finished product of the textile spinning process;

• Carded sliver
• Drawn Sliver
• Simplex Roving

1. Determination of grains/yard and CV% of Carded/Drawn Sliver:

Carded sliver is produced in the carding process by using a card machine.  In the carding process, the opening, cleaning and mixing of the fibers are carried out to produce a sliver that is suitable for subsequent processing. After carding, the drawn sliver is made by blending and doubling of carded sliver in draw frame. The carded and drawn sliver should be uniform along its length so that a uniform and regular yarn can be produced.

1.1 Materials and Equipment required for testing:

The following materials and equipment are used for the quality control testing of carded and drawn sliver;

1. Drum wrapping machine (Girth size = 1 yard)
2. Carded sliver (Sample size = 6 Yard)
3. Drawn sliver (Sample size = 6 Yard)
4. Weighing balance

1.2 Testing Procedure:

1. First of all, the sliver is obtained from the card and drawing department of a textile spinning mill.
2. The standard sample size for the quality control testing of sliver is 6 yards, which is obtained with the help of a wrapping drum.
3. Prepare 10 samples of Carded and drawn sliver having a length of 6 yards each, so that the average result is taken to minimize the variation.
4. Then put these samples on a weighing balance and note the weight of each sample in grams.
5. Then convert this gram weight into grains by multiplying with 15.43, because 1 gram weight is equal to 15.43 grains weight. Then this value will be divided by 6 to achieve the required value of grains/yard of carded and drawn sliver.
6. Then find out the mean of sliver weight.
7. Then the following formulas are used to measure the Coefficient of variation (CV %) of carded and drawn sliver.

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

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

Note: Suppose the results of the testing show that the value of (CV %) of the carded and drawn sliver is more than 1.5 %. In that case, it means that the quality of the carded and drawn sliver is not good and then the settings of the card and drawing frame will be changed to minimize the Coefficient of Variation (CV %) of the carded and drawn sliver.

1.3 Application and Try Out:

After completing the test procedure as mentioned above, the obtained data is put in the following tables for the calculation of grains/yard and coefficient of variation (CV %) of carded and drawn sliver.

Table 1.1: Calculations and Observations of Carded Sliver:

Sr. #	6-yard Carded Sliver weight in grams (A)	Sliver weight in grains/yard (X)	$\left(\mathrm{X}-\stackrel{-}{\mathrm{X}}\right)$	(${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$
1	22.47	57.79	0.44	0.19
2	22.12	56.89	-0.46	0.22
3	22.35	57.48	0.13	0.02
4	22.03	56.65	-0.70	0.48
5	22.35	57.48	0.13	0.02
6	22.26	57.25	-0.10	0.01
7	22.19	57.07	-0.28	0.08
8	22.41	57.63	0.28	0.08
9	22.39	57.58	0.23	0.05
10	22.44	57.71	0.36	0.13
		Mean ($\stackrel{-}{\mathrm{X}}$)= 57.35		$\sum$ (${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$ = 1.27

1.3.1 Standard Deviation:

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

                                        $\mathrm{S}.\mathrm{D}=\sqrt{\frac{1.27}{10-1}}$

                                        $\mathrm{S}.\mathrm{D}=\sqrt{\frac{1.27}{9}}$

                                        $\mathrm{S}.\mathrm{D}=\sqrt{.1411}$

                                        $$S.D=0.38

1.3.2 Coefficient of variation (CV %) of carded sliver:

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

                                        $\mathrm{C}.\mathrm{V}\%=\frac{0.38}{57.35}\times 100$

                                        $$C.V%=0.7 %

$$

Table 1.2: Calculations and Observations of drawn sliver:

Sr. #	6-yard Drawn Sliver weight in gram (A)	Sliver weight in grains/yard (X)	$\left(\mathrm{X}-\stackrel{-}{\mathrm{X}}\right)$	(${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$
1	19.18	49.32	0.40	0.16
2	19.16	49.27	0.35	0.12
3	18.92	48.66	-0.26	0.07
4	18.95	48.73	-0.19	0.03
5	18.96	48.76	-0.16	0.03
6	19.02	48.91	-0.01	0.00
7	18.97	48.78	-0.14	0.02
8	19.07	49.04	0.12	0.01
9	19.02	48.91	-0.01	0.00
10	18.99	48.84	-0.08	0.01
		Mean ($\stackrel{-}{\mathrm{X}}$)= 48.92		$\sum$ (${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$ = 0.46

1.3.3 Standard Deviation:

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

                                        $\mathrm{S}.\mathrm{D}=\sqrt{\frac{0.46}{10-1}}$

                                        $\mathrm{S}.\mathrm{D}=\sqrt{\frac{0.46}{9}}$

                                        $\mathrm{S}.\mathrm{D}=\sqrt{0.051}$

                                        $\mathrm{S}.\mathrm{D}=0.2258$

1.3.4 Coefficient of variation (CV %) of Drawn sliver:

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

                                        $\mathrm{C}.\mathrm{V }=\frac{0.2258}{48.92}\times 100$

                                        $$C.V =0.46 %

2. Quality control testing of the roving process in textile:

Roving material is produced in the simplex department of the Textile Spinning Mill. In a simplex frame, the drawn sliver is attenuated with different attenuating processes. It is the first spinning process where a small amount of twist insertion is carried out. The hank count of roving material should be uniform along its length so that a precise and regular yarn can be produced.

2.1 Materials and Equipment required for testing:

The following materials and equipment are used for the quality control testing of simplex roving material;

1. Drum wrapping machine (Girth size = 1 yard)
2. Simplex Roving Material (Sample size = 15 Yard)
3. Weighing balance

2.2 Testing Procedure:

1. First of all, the different roving bobbins are randomly selected from the simplex department of a textile spinning mill.
2. The standard sample size for the quality control testing of simplex roving is 15 yards, which is obtained with the help of a wrapping drum.
3. A total of 10 samples of roving material would be collected so that the average result is taken to minimize the variation.
4. Then put these samples on a weighing balance and calculate the average weight of these samples in grams.
5. Then the following formula is used for the calculation of hank roving of simplex roving material.
1. ($\mathrm{Hank} \mathrm{Roving}=\frac{8.10}{\mathrm{Average} \mathrm{weight} \mathrm{in} \mathrm{gram}}$)
6. After the calculation of Hank Roving, the following formulas are used to measure the Coefficient of variation (CV %) of simplex roving material.

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

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

Note: Suppose the results of the testing show that the value of (CV %) of the simplex roving material is more than 1.5 %. In that case, it means that the quality of the roving material is not good and then the settings of the simplex frame will be carried out to reduce the Coefficient of Variation (CV %).

2.3 Application and Try Out:

After completing the test procedure as mentioned above, the obtained data is put in the following tables for the calculation of Hank roving and coefficient of variation (CV %) of simplex roving material.

Table2.1: Calculations and Observations of simplex roving material:

Sr. #	Roving weight in gram (X)	$\left(\mathrm{X}-\stackrel{-}{\mathrm{X}}\right)$	(${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$
1	11.40	-0.1	0.010
2	11.46	-0.04	0.002
3	11.53	0.03	0.001
4	11.44	-0.06	0.004
5	11.56	0.06	0.004
6	11.49	-0.01	0.001
7	11.58	0.08	0.006
8	11.54	0.04	0.002
9	11.47	-0.03	0.001
10	11.51	0.01	0.001
	Mean ($\stackrel{-}{\mathrm{X}}$)= 11.50		$\sum$ (${\left(\mathrm{X}-\stackrel{-}{\mathrm{X)}}\right)}^2$=0.032

2.3.1 Hank Roving:

                                        $\mathrm{Hank} \mathrm{Roving} =\frac{8.10}{\mathrm{Average} \mathrm{weight} \mathrm{in} \mathrm{gram}}$

                                        $\mathrm{Hank} \mathrm{Roving} =\frac{8.10}{11.50}$

                                        $$Hank Roving =0.70

$$

2.3.2 Standard Deviation:

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

                                        $\mathrm{S}.\mathrm{D}=\sqrt{\frac{0.032}{10-1}}$

                                        $\mathrm{S}.\mathrm{D}=\sqrt{\frac{0.032}{9}}$

                                        $\mathrm{S}.\mathrm{D}=\sqrt{0.0036}$

                                        $$S.D=0.06

$$

2.3.3 Coefficient of variation (CV %) of carded sliver:

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

                                        $\mathrm{C}.\mathrm{V}=\frac{0.06}{11.50}\times 100$

                                        $$C.V=0.52%

Results and discussion:

• Grains/yard of carded sliver                                        =          57.35
• Coefficient of Variation (C.V%) of carded sliver        =          0.7 %
• Grains/yard of drawn sliver                                         =          48.92
• Coefficient of Variation (C.V%) of drawn sliver        =          0.46 %
• Hank roving of simplex roving                                   =          0.70
• Coefficient of Variation (C.V%) of roving process     =          0.52 % 

Safety Precautions:

• Length should be accurately measured.
• Weight should be accurately measured.
• The Weighing balance must be calibrated.
• Calculations should be accurate.

FAQs:

1. What are the objectives of the carding process in the textile Industry?
2. What are the objectives of the drawing process in the textile Industry?
3. What are the objectives of simplex frames in the textile Industry?
4. What is the perimeter of the drum wrapping machine?
5. How much sample size is required to measure the grains/yard and CV% of carded sliver?
6. How much sample size is required to measure the grains/yard and CV% of the drawn sliver?
7. How much sample size is required to measure the hank roving and CV% of roving material?
8. How to convert the gram weight unit into grain weight unit?
9. How to calculate the grains/yard of carded and drawn slivers?
10. How to calculate the hank roving of simplex roving material?
11. What is the formula of standard deviation?
12. What is the formula for the coefficient of variation (CV %)?

Author:

Engr. Muhammad Usman Ashraf

HOD Textile Department at TEVTA Punjab, Pakistan

M.Sc Textile Engineering (NTU, Faisalabad)

Email: usmanashraf884@gmail.com