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October 2017

Yarn Diameter Measurement/Yarn Diameter Formula

Pierce developed a formula to calculate the yarn diameter. From an experimental work, he concluded that the specific volume of cotton yarn under moderate pressure is 1.1 cm3/gm.

Yarn Diameter
Yarn Diameter
The density of cotton fibre is 1.52 gm/cm3
Yarn Diameter Formula

A specific volume of 1.1 corresponds to a yarn composed of or approximately 60% of fibre and remaining 40% being air space.

Let yarn count = N tex.
Assuming specific volume = 1.1 cm3/gm
Then, 
1.1cm3 of yarn has 1 gm weight.

Now,
1 gm of N tex has a length of 1/N km or 105/ N cm.
Hence, 
1.1cm3 of yarn has a length of 105/ N cm.

Since, 
Yarn Diameter Formula

Yarn Diameter Formula
d= yarn diameter in cm.

Yarn Diameter Formula

Yarn Diameter Formula

Yarn Diameter Formula

Converting cm into inches and tex to Ne

Yarn Diameter Formula

Yarn Diameter Formula

What is Cloth Cover Factor?

Cover factor is nothing but the numerical value indicating the extent to which the area of a fabric is covered by component yarns. Fabric cover of fabric is denoted by k.

Cover Factor Formula
Cover Factor Formula

There are two cover factors for woven fabric:

  • Warp cover factor
  • Weft cover factor
In cotton system cloth cover in particular direction (warp cover factor or weft cover factor) is calculated by taking the ration of threads per inch and square root of the yarn count (cotton count/English count).


What is concept of Similar Cloths?

Two fabrics may be manufactured using same raw material but they may differ in other parameters like:
  • Yarn Count
  • Twist in Yarn
  • Thread Density (EPI, PPI)
  • Weave etc.
When two fabric samples are having same cover factor but they differ in above mentioned points then they are called as similar cloths.


Factional Cover & Derivation of Cover Factor

Fractional cover may be defined as the fraction of the total fabric area that is ‘covered’ by the component yarns.
Factional Cover
Factional Cover
Relative closeness of yarns in a woven fabric depends on the ration of yarn diameter (d) & yarn spacing (s). This ratio of yarn diameter (d) to yarn spacing (s) is known as relative cover.

Relative Cover=d/s,
Percentage Cover= (d x 100)/s 

Cloth Cover Factor

Cloth Cover Factor

In ideal model, ‘S’ will be equal to 1/n, where n is the number of threads per unit length.

The fractional cover could be expressed in terms of d and n, i.e.

Fractional cover = d ×n
With a woven fabric, two values of the fractional cover are necessary, one for warp and one for the weft.

When staple fibre and multifilament yarns are considered, yarns flatten in fabrics and assume non-circular cross-sections. One approach to this problem is to assume that the yarn cross section is still circular and derive a formula for yarn diameter.

Pierce has derived a formula for cotton spun yarn diameter as below:
Cloth Cover Factor
Using this value of yarn diameter in fractional cover,
Cloth Cover Factor




Total Cover Factor

Let us consider a simplified version of one-unit cell of a plain weave as shown in below figure.

Total Cover Factor
Total Cover Factor
The unit cell is rectangular ABCD.

The shaded area is the part of the total area covered by both yarns, and, because of this, it would not be strictly accurate to add the warp and weft cover values together and quotes as the total cover.

The shaded areas are each d1 × d2.
And the total area of the cell is S1 × S2
By definition,
Cloth Cover Factor

Cloth Cover Factor

Cloth Cover Factor
Hence,
d1=C1XS1
d2=C2XS2
Now the area of the shaded portion is,

d1×d2=C1C2×S1S2

Expressed as a fraction of the total area S1S2,

The shaded area (d1×d2)becomes,
Cloth Cover Factor
Cloth Cover Factor
The term C1 C2 must be deducted from the sum of C1 and C2.
 Hence,

Cloth Cover Factor

Cloth Cover Factor

Cloth Cover Factor

Cloth Cover Factor

Cloth Cover Factor

Multiplying by 28

Cloth Cover Factor

Cloth Cover Factor

Sushant Raghunath Desai
DKTE’S Textile and Engineering Institute, Ichalkaranji-416115 (MH), India.




In this article we are going to learn about gauze/leno fabric, traditionally it also called “Gaza”[1]. In this fabric basic principle contains Crossed End and Standard End which bound by weft position. In this we are going to learn different methods of producing fabric weave, and also different characteristic of fabric. Gauze fabric allows light and air to pass though freely so, used as any area and have various applications. We also conclude that Gauze is as same as Leno.


Gauze and Leno Fabric
Gauze and Leno Fabric


1.Introduction

Leno weave also called as Gauze weave or Crossed weave was traditionally woven in Palestine [1] and the English word is said to derive from the place name for Gaza a center of weaving in the region. 

Gauze is thin, translucent fabric with loose open weave. In technical terms “gauze” is a weave structure in which the weft yarns are arranged in pairs and are crossed before and after each warp yarn keeping weft firmly in place. It produces an open fabric with almost no yarn slippage miss placement of weft which causes the durability of fabric. This weave structure is used to add stability to fabric, which is important when using fine yarns loosely spaced
[2]. 

Gauze and Leno
Gauze and Leno
 It was originally made of silk and was used for clothing. It is now used for many different things, including gauze sponges for medical purposes. When used for medical dressing, gauze is generally made of cotton [1,5]. It is especially useful for dressing wounds where other fabrics might stick to the burn or laceration.
The yarn used most frequently in the manufacturing of these fabrics are cotton, spun rayon staple, polyester blend, filament polyamide, glass and occasionally silk.



2. Principle Construction of Leno and Gauze Fabric

In gauze and leno weaving certain ends-termed crossing ends are passed from side to side of what are termed standard ends, and are bound in by the weft in this position.

[3] A crossed system of interlacing can be obtained when all the warp is bought from one beam, and to produce some other desired effect. For producing this effects two ends are required from different beams are used. Warp yarn are crossing and standard end are combined in stripe in which ends are interlaced in ordinary manner so as to form required weave. 


Term leno may applied to all the structure in which ends are transferred from one side to other of standard end, while gauze is open structure or that of same as leno.


Gauze and Leno Fabric
Structure
Although there exist a number of mechanically different system to achieve the necessary lateral movement of one thread in respect of another the resultant structure produced by each of each of them may be identical. The thread manipulations required to produce the simplest structure of this type known as the plain leno or gauze are depicted in figure above. At A and B respectively cross-sectional views of two successive sheds are in which at A the crossing end (black) forms the top shed on of on the left of the standard (white), and at B on right of the standard end. Thus in plain leno using bottom douping system illustrated at A and B, the crossing end is up and the and the standard end is down on every pick but in between each between each successive shed the crossing end under the standard end prior to each lift and weft is held between the half twist of crossing end. The interlacing diagrams C and D show the appearance of the plain leno structure, the former obtained when one beam is used and the distortion of both the sets of ends is equal, and latter achieved when crossing end are placed on lightly tensioned beam and, therefore, bend permanently, and the standard end lie straight being placed on heavily tensioned beam. At E and F in figure above two other structure are given which corresponds respectively with C and D but differ from them that the alternate vertical rows of leno in former two are pointed drafted. This in effect means that whilst in one row the crossing end on given end on given pick crosses from left to right, in next row the crossing end on the same pick crosses from right to left. Diagram G shows a section of plain leno structure cut through the weft whilst the appearance of a plain leno cloth is described in fig.

2.1 Methods of Manufacturing

The method of controlling the crossing end is given in fig.3.1 below. It has produce only in handloom weaving and with slow speed. But to produce selvedge for leno it is not applicable for modern type of high speed type of weaving machine[4]. The main method of producing of leno and gauze structure may listed as
  1. Flat steel doups with eye.
  2. Flat steel doups with slot.
  3. Gauze and tug reed mechanism.
  4. Eyed needle and slider frame device.
  5. Rotating bobbin and geared disc mounting.
The last method is different than other first four method, due to formation of twisted of thread in weaving but as it is only applicable for producing leno selvedge it cannot be regarded as formation of cloth. 



3. Weaving

3.1 Gauze Heald Shafts & Doup Heald

To weave plain gauze we require two ordinary healds called as doup heald. The two ordinary heald shafts are hung in the loom in the ordinary way, the odd number of warp ends healded through shaft 2, counting from front to back, and even number of heald shaft 1. Three or four inches in front of these two shafts, and between it and the cloth fell, the heald shafts characteristic of the gauze loom are hung. These are a whole heald shafts, designed the stan board, and the half heald shaft named for our purpose the doup. Within the heald eyes of standard, the eyes of half heald shafts are looped, or secured. From back heald shaft, the odd-numbered warp ends are crossed under even number of ends, and through the healds on the doup.

Primarily, the object of this structure is to obtain a means of making the odd threads of the warp lift nearly two thread round the even thread. If crossed thread are lifted, being already passed under the other ends, they will naturally be almost round them. If the warp and weft are to be woven into plain cloth, the alternate crossing of the pair of common heald shafts will not be interfered with by the crossing standard and doup, because the doup moves easily up and down on the standard, in obedience to the lift of the second heald shaft 
[4].

Structure of Standard End & Crossed End in Plain Gauze
Structure of Standard End & Crossed End in Plain Gauze
There are really several methods of weaving plain gauze. On the oldest method, the mounting consisted of two back leaves of common heddles, two front leaves, then named pause over this method, due to it is discarded. In early two methods are employed same number of heald shafts but in other ways. 
In this method in mounting one warp end and heald shaft in undermost and stationary. In back heald shafts all the crossing threads are healded and in front shaft carries stationary ends. This crossed ends arepassed through doup, for plain weaving we have heald shafts 1 and 2 crossing and doup heald should raising with shaft 2. When fabric to be woven front shaft never moves as it simply holding down the warp end being crossed, as there should be action in between back heald shafts and the doup. On pick 1 the doup is lifted, while at same time two heald shafts are depressed, on pick 2 the doup and heald shafts are lifted, as 1 remain depressed. As the action of first motion is that lift crossing thread over standard ends, and there will be appropriate weft insertion takes place. On the second action crossing threads on other side of standard threads and weft insertion takes place so in this two action thus made proper shed.

Method of Weaving Plain Gauze/Leno.[ Book of Watson’s Advanced Design]
Method of Weaving Plain Gauze/Leno.[ Book of Watson’s Advanced Design] 
In newer method, instead of being always at stand the standard end always lifted. We have to assume four picks and four ends. On pick 1 heald shafts 2 and the doup heald are lifted; on pick 2 the two heald shafts re lifted and doup are remains stationary. On pick 3 heald shafts and doup are lift, on pick 4 heald shaft 1 and 2 lifted. As we understand that pick 1 and 3 are open shed is made, crossing warps end on one side of standard end; on pick 2 and 4 a crossed shed is formed, with the crossing warp end on other of its neighboring standard end. Through each shed weft pick has flows.



4. Characteristics of Leno and Gauze Fabric [3]

  • The gauze weave construction produces a fabric very light in weight and with an open mesh effect.
  • Leno weaves also produces curtain materials, some shirting and dress goods.
  • This weave produces such light-weight fabrics have strength that could not be provided by plain weave.
  • The gauze weave sometimes referred to as the leno weave because it made on leno loom.
  • On leno loom, the action of one warp yarn is similar to action on plain weave.
  • The doup attachment, a hairpin-like device at the heddle, alternately pulls the second warp yarns up or down to right or left with each pick passage. This cause the pair of warp yarn to be twisted, in effect, around each weft yarn.
  • The leno is sometimes used in combination with the plain weave to produce a stripe on a plain back ground.
  • The fabric weight varies depending upon thickness of the yarns, which could spun.



5. Applications of Gauze and Leno Fabric

Leno weave fabric allows light and air to pass through freely so are used in any area where a sheer, open weave fabric is required that will not bruise. If a simple in-and-out flat weave were woven very loosely to achieve the same effect the threads would have a tendency to this brushing.
Applications of Gauze and Leno Fabric
Applications of Gauze and Leno Fabric

5.1 Madras Muslin

It is cotton fabric of plain weave. It is made in a wide range of weights from delicate sheers to coarse sheeting. It get its name from the city of Mosul, Iraq, where it may have been first manufactured [5].

When sewing clothing, a dressmaker may test the fit of a garment, using an inexpensive muslin fabric before cutting pieces from expensive fabric, Thereby avoiding costly mistakes. This garment is often called “Muslin”. 

5.1.1. Theater and Photography

Muslin is often the cloth of choice for theater sets. It is used to mask the Background of sets and to establish the mood or feel of different scenes. It receives paint well and, if treated properly, can be made translucent.
It also holds dyes well. It is often used to create nighttime scenes because when dyed, it often gets a wavy look with the color varying slightly, such that it resembles a night sky. Muslin shrinks after it is painted or sprayed with water.

5.1.2. Medicine

Surgeons used Muslin gauze in Cerebrovascular (Type of Disease) neurosurgery [6] to wrap around intracranial vessels at risk for bleeding. The thought that the gauze reinforces the artery and helps prevent rupture.

5.2 Mosquito Net

Mosquito netting can be made from cotton, polyethylene, polyester, polypropylene [8]. A mosquito bar is an alternate form of a mosquito net. It is constructed of a fine see through mesh fabric mounted on and draped over a box shaped frame.

5.3 Agro Textiles

5.3.1. Shed Nets

The warp-knitted nets are used in order to protect fields and greenhouses from the intense solar radiation for healthy plant growth and good harvest. So the excess heat does not entered under the screen.

Also the humans specially Ladies, they use scarp to protect the face or body from high sun radiations and from pollution. The fabric which is woven is light in weight and having attractive design.

5.3.2. Bird Net

Knitted monofilament nets offer effective passive protection of seeds, crops, fruit against damage caused by birds and a variety of pests.

5.3.3. Nets of Covering Pallets

For safe transportation of fruits and veg. to the market the boxes are covered with large mesh nets and pallets to stop the boxes being turned upside down. This prevents damage of goods during transportation.

5.4 Sheer Curtain 

A common use for sheer fabric is in curtains, which allows for sunlight to pass through during daylight. Due to loose weave in sheer fabrics curtains offer little heat insulation. When it is lighter on the inside of a room than it is on the outside, then inside of the room can be seen from the outside. It is also used in dancing wear, wedding gowns and formal costumes.

5.5 In Chemistry

There are two types of wire gauze used in chemistry: a normally woven wire gauze, and one with white circle imprinted on it. The latter is ceramic composite intended to aid in dispersal in heat.


6. References

  1. Gauze Wikipedia (History and Uses).
  2. Watson’s Advanced Textile Design, Edition IV, Z J Grosicki (208, 209, 211).
  3. Textile Weaving and Design, W S Murphy.
  4. Textile Apex (Applications Of Agro-Textiles ),Textile In Agriculture- Saiful Sabuz.
  5. Leno Wikipedia (On-line Digital Archive of Documents on Weaving and related topics: Leno weaves, International Textbook Company.)
  6. Muslin Wikipedia (Muslin, Oxford English Dictionary, Third Edition. Webster’s Unabridged Dictionary. )
  7. Agreetextile Wikipedia.
  8. Mosquito net Wikipedia.
  9.  Knitted Views (volume 12/issue No:04)


[alert title="Note" icon="info-circle"] The information and views set out in this article are those of the author(s) and do not necessarily reflect the official opinion of Online Textile Academy. Neither the Founder and Editor nor any person acting on their behalf may be held responsible for the use which may be made of the information contained therein. [/alert]

4 Point Inspection System

Prof. Ravikumar N. Purohit
Assistant Professor
D.K.T.E. Society's Textile and Engineering Institute, Ichalkaranji-416115

What is 4 Point Inspection?

4 point inspection system is most widely used system for fabric inspection method. This system is used in weaving after fabric making and in garment industries in fabric department.

Objective behind 4 point inspection in both the cases is to analyze fabric quality.

For weaving

If fabric contains very less faults then weaver can sell this fabric at higher rate as fabric is having good quality. If buyer is already fixed then weaver will come to know whether fabric which has been produced satisfies customer requirement or not.  

For Garment industry

To decide whether fabric roll is acceptable for next process or they should reject the roll and lot.




4 Point Inspection System
4 Point Inspection System


Process of 4 Point Inspection

To analyze the fabric after fabric making

  1. The roll is taken on inspection machine as shown in the image
  2. A standard sheet as per company format is given to the operator
  3. Operator fills the required details of fabric such as sort, color, actual width and actual length.
  4. Defects in both warp as well as weft directions will be assigned and marking of defects is done with the chalk or sticker
  5. Points under the following criteria with respect to length has to be given. Following chart of 1-4 points marking is given.
  6. Total points has to be summarized with actual length and actual width.
  7.  Finally calculation is to be done which will give total number of fabric defects per 100 square yard. 


Fabric Inspection
Fabric Inspection



How Points are Assigned?



Defect Range Points Evaluation
Up to 3 inches 1 Point
Greater than 3 inches and less than 6 inches 2 Points
Greater than 6 inches and less than 9 inches 3 Points
Greater than 9 inches 4 Points
Hole in the fabric less than 1 inch 2 Points
Hole in the fabric greater than 1 inch 4 Points



Individual Roll Points

The following formula is used to determine the point count for each roll.

Formula Points per 100 square yard
Formula Points per 100 square yard

Formula Points per 100 square yard
 = (Total points found in roll * 36*100) / (Inspected length in yard * Fabric width (inches))

Example

Decision for roll acceptance or rejection for inspected roll length of 100 meter with width 50 inches and it contains following defects.


5 defects less than 3 inches 5*1= 5 points
4 defects between 3-6 inches 4*2= 8 points
2 defects between 6-9 inches 2*3= 6 points
2 defect on full with in weft 2*4 =8 points

Total points are: (5+8+6+8 =27 points)
Inspected length is 100 meter: 100*1.093= 109.3 yard
Width in inches: 50

As per formula total points per 100 square yard = 
(27*39.37*100)/(109.3*50)= 19.45

Now here comes a question- Should we reject the roll or accept the roll.


Acceptance or Rejection of Roll

So the conclusion of Acceptance or rejection of roll purely depends on company policy. What criteria they have like some companies follow 40 points means if they have less than 40 defects per 100 square yard then they will accept this roll. While some companies follow 24 points. So here in both the cases fabric is acceptable.



So with this formula, productivity is defined as it is the ratio of OUTPUT to INPUT.

  1. Productivity is a measure of the efficiency which indicates how inputs are utilized.
  2. So here in apparel industry output is taken as number of garments produced.
  3. Input we can take in terms of – Labor, Machine and Time.
  • Labor productivity: If we take labor as input then this will indicate no. of pieces produced per labor.
  • Machine productivity: If we take machine as input then this will indicate no. of pieces produced per machine
  • Value productivity: If we take time as an input then this will indicate no. of pieces produced per unit time.


Productivity Improvement
Productivity Improvement



Simple Ways to Improve Productivity

There are 3 simple ways to improve productivity in apparel industry and all 3 ways are directly related to formula.

  1. Increase the output with same input.
  2. Decrease the input with same output
  3. Little increase in input with greater increase in output.

[alert title="Let us understand all 3 ways with a simple example." icon="info-circle"]
Consider a garment factory with 10 operators and they are producing 50 pieces per day. With this situation the labor productivity is 5 pieces per operator. Now to improve productivity we can choose any one method to improve productivity.

[/alert]

1) Increase the output with same input.

In this case we are asking to the group of 10 operators for more output that means instead of 50 we are asking 55 pieces per day. Suppose they achieve this that means productivity will improved 55/10 = 5.5 pieces per operator.

2) Decrease the input with same output

In This case we are asking same output means 50 pieces but with lesser man power that means if they achieve same output with 9 operators. The productivity will increased to 50/9= 5.55 pieces per operator.

3) Little increase in input with greater increase in output.

In this case we are asking more output with little increase in input like we are asking 60 output with 11 operator in a line instead of 50 pieces with 10 operator. If they achieves this then productivity will increase to 60/11= 5.45 pieces per operator.

Spreading must achieve a number of specific objectives. The following points should be taken care off while spreading plies of fabric to form lay in order to achieve good cutting quality.


Requirements of Spreading
Requirements of Spreading 


1. SHADE SORTING

The process of sorting of rolls according to shade is known as shade shorting. Lays commonly require more than one roll of fabric to achieve enough plies in total. So obviously different lot or roll won’t have an exact shade match and garment made from parts cut from the rolls of different shade lot would most likely show a shade variation between its different panels. Shade variation is already a big quality problem for garment industries. One garment- One shade this is been normally followed by every industry.

So, to avoid shade variation number of rolls of cloths of the same color are received, they should be sorted into batches such that shade differences between them are undetectable.




2.CORRECT PLY DIRECTION

There are various types of fabrics, in terms of surface direction, that are available in market which are designed either way, one way – either way or one way only. If fabric don’t have any particular nap direction then we can place pattern in any way according to grain line but if fabric have nap direction then we have to position pattern pieces in the same direction in the marker plan, so it is essential that the fabric is spread in a way that maintains that same direction. One garment- One shade-one direction this is been normally followed by every industry for napped fabric.

The best examples of such fabrics are velvet where change in the direction of pattern placement would clearly show on the garment as different. Parts of the garment would show the nap of the fabric in different directions.




3. LAY STABILITY

The number of plies that to be spread in one particular lay depends on the thickness of the fabric and also the equipment being used for cutting. As such, a thicker fabric such as denim would have less plies in a lay, whereas a sheer fabric such as chiffon would have more plies in a lay. Care should be taken to spread neither too less nor too much extra plies then the prescribed no of plies in a lay to provide lay stability when the cutting equipment cuts through the plies. Also, lay should be stable it should not get shrink before cutting this precaution is very important in wool fabric and fabric consist of Lycra yarn.



4. PLY ALIGNMENT

Ply should comprise the width and length according to marker plan, but should have the minimum possible extra length and width outside those measurements. All the plies should be aligned to the edges form one side at least.


Fabric Spreading
Fabric Spreading


5. WIDTH OF FABRIC

Width is the base of marker planning and the different fabric width in rolls causes fabric loss. Fabric loss will be least if all the rolls will have same width but the nature of textile material is such that the pieces of fabric as delivered from suppliers, vary in width, both from role to role and to lesser extent within role. The marker plan is made to fit the narrowest width. The extra width of the fabric is distributed outside the edge of the marker plan. At the end the ply should be cut off squarely allowing the minimum loss at both the ends.



6. CORRECT PLY TENSION

It is important for the spreading to have correct ply tension i.e. neither slack nor stretched before cutting the fabric into garment parts. If the plies are spread with very low tension they will lie in ridges with irregular fullness. If plies are spread in a stretched state they will have tension while held in the lay, but will contract after relaxation or after cutting or during sewing, thus it causes shrinking the garment parts to a smaller size than the pattern pieces. This will increase the garment rejection as measurement are very important in export quality garments.



7. FABRIC FAULTS IDENTIFICATION AND ELIMINATION

In fabric store fabric is been audited by 4-point inspection/ 10-point inspection but it is possible that some faults which somehow got missed should be marked with some identification so that they can be identified after cutting and faulty parts are changed. Also, spicing can be done to eliminate the fabric faults in spreading itself.



8. AVOIDANCE OF DISTORTION IN THE SPREAD

A layer of brown paper is spread at the bottom of spread in which laid glazed side down and rough side up. This helps to avoid ply slippage problem of the lowest plies of material in the spread when the straight knife base plate passes underneath. The glazed side of the paper facilitates the movement of straight knife within the spread and also if it is to be moved on a floatation table. The rough side gives stability to the lay by providing better friction between the paper and the lowest ply of fabric.

Ashish Hulle

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