Textile Costing, Fabric design, Weaving Calculation, woven fabric formation

This is an amazing website on textile costing, fabric design, weaving calculation and woven fabric formation. A must for a web textile technologist.

warp preparation for rope dyeing-1

Warp Preparation Requirements for Rope Dyeing

Ball Warping: Equipment required to form the rope of yarn. It involves creeling multiple ends of yarn ( Between 350-500 ends) and collecting them into an untwisted rope for dyeing. the rope is wound onto a long cylinder called a log on a machine called as a ball warper.

Some Notes

1. Packages of yarn are preconditioned before ball warping
2. Packages are loaded into the creel ( larger lots- magine transefer creeL0 and smaller lots- swing gate or truck creel
3. Packages are placed on adapters. An adapter support the package of yarn and ensure that the package remains aligned to the tensioning devices. Wooden plug type adapter are most effective as they require least amount of exertion to remove the empty package.

Next Step is threading the tensioner located at each yarn package

1. Post and Disk tensioner. It has two posts mounted onto a flat base. two round disk are placed onto each post. The yarn is threaded between the disk and wrapped around the post. One of the parts is movable so that the angle of wrap can be varied. More tension can be added to the yarn by adding round weights onto the top disk.

Advantages are 1. Inexpnsive 2. does Marginally adequate job of maintaining yarn tension 3. Simple to thread up 4. Low maintenance requirements.

Disadvantages are 1. Yarn has a tendency to jump out from between the disks at the rear of the creel. 2. It is labour intensive- when different tension levels are required. 3. There is more frequency of cleaning up 4. It doesnt control tension well at higher speed.

2. The driven disk tensioner

It also uses twin disk arrangement, however the disks are supported from below- there are no posts. Tension is applied from above- there are weights or spring loaded.
A gear under each pair of disks is matched to another gear mounted on a continuous shaft which runs the length of the vertical tension post. This shaft is connected to a 4 rpm motor which rotates the disk.

Advantage of disk rotation are 1. Thread cutting prevention 2. Dampens out variation due to ballooning action of yarn. There is mor uniform tension 4. Less effor required to change tension levels.

Disadvantages are 1. It is more difficult to thread up, there is more maintenance due to electric motor used and at high speed the tension control is not well.

loom shed

Process Control in Loom shed

It consists of two parts:
1. Increasing machine productivity
2. Improving quality or reducing defects

Control of the productivity can be done with

1. controlling nominal loom speed close to currently set standards.
2. Ensuring that loss of speed through belt slippage is minimum
3. Control of loss of loom efficiency by minimising:
a. Loom stoppage rate through correct maintenance
b. Control of down time of loom through corrective action on the basis of data collected by snap reading.

1.
2.

3. Factors effecting Loom efficiency

Various factors that affect the loom shed efficency are

1. Technical
2. Human ( Related to weaver skill and work methods)
3. Organisational

Relating the three factors

The technical and human (weaver related) factors have a very basic relationship with loom efficiency. The relationship is

P = NEX
= NE at

or E = P/ Nat
Where P= operative efficiency
N= number of machines per operative
E= Machine efficiency

X= Service factor, and it is equal to the average time taken to clear the stops in unit running time of a machine and equals at.
a= average no of stops per unit running time of a machine
t= average time to clear a stop including walking time

Thus if during an hour, the operator spends on an average 30 minutes in clearing stops, 15 min in ancillary durites like bringing raw materials etc and 15 min on rest and relaxation then
operative efficiency = (30 x 100)/60 = 50%
Work load = (30+15)x100/60 = 75%

Thus to maximise loom efficiency
- The stoppage rate should be low
- the weaver should be trained so that he takes the minimum possible time for clearing a stop.
- the operative efficiency should not fall below the optimum level
- loom allocation should be optimum

Costing in Drawing-in

Costing in Drawing-in

Drawers and reachers are paid their basic wages on piece rate system. The rates are related to the type of cloth to be woven. the basis of allocation of expenses to the different types of cloths are

1. Basic Wages of drawers and Reachers= Rate per 1000 ends x total production in 1000 ends.
2. DA to drawers and reachers and all other expenses = total production/production per shift

Cost of Drawing-in

Unit costs of this process as cost per 1000 ends. The cost of this process is calculated as shown below:

Cost of drawing-in per piece lengtrh = (cost per 1000 ends x total no of ends x tape length)/ weaver's beam length

Reed Calculations

Reed Calculations

In weaving, the reed is an important part of the loom. It helps to keep the warp ends evenly spaced and also helps in beating the weft into the fell of the cloth. Therefore, understanding reed count is essential for calculating the number of warp ends per inch in the fabric.

Reed calculations are often taught in a very short form, but a small mistake in terminology can create confusion. The reed count tells us about the number of dents, while the actual ends per inch depend on how many warp ends are passed through each dent. Similarly, heald calculations are related to the distribution of warp ends across shafts, not to the reed itself.

Table of Contents

• Stockport Reed System
• Particulars of Reed While Ordering
• Example 1: Finding Ends per Inch from Reed Count
• General Formula for Stockport Reed Count
• Plain Set and Heald Count
• Example 2: Heald Count for a 6-Shaft Satin Fabric
• Important Distinction Between Reed Count and Heald Count
• Summary
• Corrected Key Points
• General Disclaimer

Stockport Reed System

Reeds are commonly counted by the Stockport system. In this system, the reed count is based on the number of dents in two inches. This point is important. The Stockport system does not directly tell us the number of warp ends in two inches; it tells us the number of reed dents in two inches.

For example, a 72s Stockport reed means:

\[ 72 \text{ dents in 2 inches} \]

Therefore:

\[ \text{Dents per inch} = \frac{72}{2} = 36 \]

So, a 72s Stockport reed has 36 dents per inch. If one end is passed through each dent, the ends per inch will be 36. If two ends are passed through each dent, the ends per inch will be 72. If three ends are passed through each dent, the ends per inch will be 108.

Visual 1: Stockport reed count explained as dents in two inches and converted into dents per inch.

Particulars of Reed While Ordering

A reed may be specified as:

100s ST, 18 G., 44" × 5", blue

This means that the reed has a Stockport count of 100. Since Stockport count is based on two inches, this means that the reed has 100 dents in two inches, or 50 dents per inch.

• 100s ST: Stockport reed count is 100.
• 18 G.: The reed is made using dents of 18s wire gauge.
• 44": The reed is 44 inches long.
• 5": The reed is 5 inches deep.
• Blue: There will be blue paper on the baulk of the reed.

Here, “ST” refers to Stockport. The count tells us how many dents are present in two inches. The actual ends per inch will depend on the draft plan and the number of ends drawn through each dent.

Example 1: Finding Ends per Inch from Reed Count

Question: What will be the number of ends per inch at the reed in a reed of 3/80s Stockport?

Here, 80s Stockport means:

\[ 80 \text{ dents in 2 inches} \]

Therefore:

\[ \text{Dents per inch} = \frac{80}{2} = 40 \]

The expression 3/80s Stockport means that the reed is being drawn with 3 ends per dent.

Therefore:

\[ \text{Ends per inch} = 3 \times 40 = 120 \]

So, the reed will give:

\[ \boxed{120 \text{ ends per inch}} \]

This calculation is correct. However, it is technically clearer to say “ends per inch at the reed” rather than “ends per inch in the reed.” The reed contains dents; the warp sheet contains ends.

General Formula for Stockport Reed Count

For a Stockport reed:

\[ \text{Dents per inch} = \frac{\text{Stockport reed count}}{2} \]

If there are \(n\) ends per dent, then:

\[ \text{Ends per inch} = \frac{\text{Stockport reed count}}{2} \times n \]

Or:

\[ EPI = \frac{R \times n}{2} \]

Where:

• \(EPI\) = ends per inch
• \(R\) = Stockport reed count
• \(n\) = number of ends per dent

For example, if a reed is 72s Stockport and the drawing is 3 ends per dent:

\[ EPI = \frac{72 \times 3}{2} = 108 \]

Thus, the fabric will have 108 ends per inch at the reed, assuming no other change due to contraction, crimp, or finishing.

Visual 2: Formula flow showing Stockport count, dents per inch, ends per dent, and final ends per inch.

Plain Set and Heald Count

When a set contains 4 shafts, it is called a plain set. The count of healds is expressed by the number of heald eyes per inch across the complete set of shafts.

For example, a 60s plain set means:

\[ 60 \text{ heald eyes per inch across 4 shafts} \]

Therefore, the number of heald eyes per inch per shaft is:

\[ \frac{60}{4} = 15 \]

So, in a 60s plain set, each shaft has:

\[ 15 \text{ heald eyes per inch per shaft} \]

If the same total of 60 heald eyes per inch is distributed across 6 shafts, then:

\[ \frac{60}{6} = 10 \]

So, for a 6-shaft set, each shaft would have:

\[ 10 \text{ heald eyes per inch per shaft} \]

This distinction is useful because the reed controls spacing at the reed, while the healds control the lifting and lowering of warp ends according to the weave structure.

Example 2: Heald Count for a 6-Shaft Satin Fabric

Question: Find the count of healds required for weaving a 6-shaft satin fabric using a 72s Stockport reed, drawn 3 ends per dent.

First, calculate the dents per inch:

\[ \text{Dents per inch} = \frac{72}{2} = 36 \]

Since the reed is drawn 3 ends per dent:

\[ \text{Ends per inch} = 36 \times 3 = 108 \]

So:

\[ EPI = 108 \]

Now, the fabric is woven on 6 shafts. Therefore, the number of heald eyes required per inch per shaft is:

\[ \frac{108}{6} = 18 \]

So, each shaft must have:

\[ 18 \text{ heald eyes per inch} \]

To express this in terms of an equivalent plain set, remember that a plain set has 4 shafts. Therefore:

\[ \text{Plain set equivalent count} = 18 \times 4 = 72 \]

Thus, the required heald arrangement is:

\[ \boxed{18 \text{ heald eyes per inch per shaft on 6 shafts}} \]

Or, expressed as a plain-set equivalent:

\[ \boxed{72s \text{ plain-set equivalent heald count}} \]

Visual 3: Heald count calculation showing 108 EPI divided over 6 shafts and converted to plain-set equivalent.

Important Distinction Between Reed Count and Heald Count

A common confusion in weaving calculations is between reed count and heald count. The two are connected through warp density, but they are not the same thing.

A reed count tells us how many dents are present in a given length. In the Stockport system, this length is two inches. The reed controls the spacing of warp ends at the reed and helps beat the weft into the fabric.

A heald count tells us how many heald eyes are available per inch across the set of shafts. The healds control the lifting and lowering of warp ends according to the weave design.

Therefore, reed calculations are mainly concerned with:

\[ \text{Dents per inch and ends per dent} \]

Heald calculations are mainly concerned with:

\[ \text{Ends per inch and number of shafts} \]

Point of Comparison	Reed Count	Heald Count
What it refers to	Number of reed dents	Number of heald eyes
Main function	Spaces warp ends and beats the weft	Controls warp lifting according to weave design
Key calculation	Dents per inch × ends per dent	Total EPI divided by number of shafts
Common mistake	Calling dents “ends”	Confusing heald count with reed count

Related Reading on Weaving and Textile Calculations

• Textile Calculations: How to change the EPI and PPI when changing counts for a given fabric
• Warp and Weft Calculations: How to Make a Fabric Heavier Without Changing Its Character
• Calculations: Changing Cloth Weight and Weave Pattern While Keeping the Same Structure
• Textile Calculation: Finding the Length and Weight of Yarn in a Given Length of Cloth
• How to calculate the weight of Fabric

Summary

The Stockport reed system is based on the number of dents in two inches. To find dents per inch, divide the Stockport reed count by 2. To find ends per inch, multiply the dents per inch by the number of ends drawn through each dent.

For a 3/80s Stockport reed:

\[ \frac{80}{2} \times 3 = 120 \text{ ends per inch} \]

For a 6-shaft satin fabric using a 72s Stockport reed with 3 ends per dent:

\[ \frac{72}{2} \times 3 = 108 \text{ ends per inch} \]

Then:

\[ \frac{108}{6} = 18 \text{ heald eyes per inch per shaft} \]

And the plain-set equivalent heald count is:

\[ 18 \times 4 = 72 \]

So, the correct conclusion is:

\[ \boxed{\text{Required heald count = 72s plain-set equivalent}} \]

Or:

\[ \boxed{\text{6 shafts with 18 heald eyes per inch per shaft}} \]

General Disclaimer

This article is intended for educational understanding of basic weaving calculations. Actual production values may vary depending on loom type, yarn type, yarn tension, weave structure, crimp, reed space, drawing-in plan, fabric width, finishing shrinkage, and mill practice. The calculations shown here should be used as a technical starting point and should be verified through sampling before final production.

Process Control in Drawing-in

Process Control in Drawing-in

The term drawing-in and warp tying refers to the operations involved in preparing the weaver's beam for the purpose of weaving fabrics on the loom.

The drawing-in process primarily consists of drawing ends from the weaver's beam through heald eyes of different harnesses and then through the dents of a reed in the order that is determined by the design of the fabric.

If a beam is to be worked with warp stop motion on the loom, specially when using closed drop-pins, the ends have to be drawn through these pins before drawing them through the heald eyes and reed dents.

conventionally drawing-in is carried out manually by two persons-one, the reacher for selecting and presenting the ends from the beam, and the other, the drawer for pulling ends through the drop-pins, heald eys and reed dents.

The main requirements of carrying out this process properly and efficiently are:

1. The operator should be aware of the principles of drawing-in and be trained to do the job speedily because any mistakes or delays in carrying out the process would prove to be costly.

2. The healds and reeds should be in good condition and of suitable specifications for ensuring that these are not the cause of warp breaks on the loom and of defects in the fabric.

3. The drawing of the beam should be done properly to avoid cross ends on the beam.

4. Suitable precautions should be taken to reduce the incidence of extra-ends and to compensate for the missing ends during the weaving of the loom.

CARE OF HEALDS AND REED

1. The healds and reed from the exhausted beam of the loom must be cleaned throughly to free them from fluff, size, rust etc. before using them for a new weaver's beam.

2. When warp tying is practiced, it should be ensured that the same set of healds and reed do not work on the loom for a long time, even if no apparent defect is noticed in them. This is because through cleaning of healds cannot be done on the loom itself and dirty healds are prone to give high warp breaks.

COMMON DEFECTS IN DRAWING-IN

1. Cross ends- To minimise the incidence of cross ends on the beam during weaving, the ends presented for drawing in or warp tying should be made to be parallel and in their respective positions as in the beam. Proper dressing of ends is, therefore, of great importance.

2. Extra Ends- some ends are generally cast out during drawing-in/warp tying to compensate for long missing ends on the weaver's beam.Whether to leave these ends or not should be governed by the method of cutting lappers at sizing.

If the lappers are cut and mended only after completion of a weaver's beam, there is no need of leaving extra-ends at drawing-in or warp tying. If however, the lappers are cut no sooner these are detected, the same ends should not be withdrawn or not taken for tying.

Cost of Sizing

Cost of Sizing

The cost of sizing ( excluding cost of sizing chemicals) is generally expressed as cost per unit length. Hence contribution of sizing cost can be calculated as:

cost of sizing= cost per unit length x tape length

cost of sizing chemcials is expressed as cost per unit length of size mixture. The cost per piece of fabric can be calculated as:

Cost of sizing chemicals per piece length= cost/kg x (warp weight per piece length x size add on %)

Basic stitches- Animation

Basic Stitches Animations

This site talks about how sewing machine works. It is replete with animations. It starts by saying that it was inefficient to mechanically copy the process of hand sewing. This site has animations for the following stitches:

1. Basic chain stitch
2. Twisted chain stitch
3. Lock stitch
4. Oscillating hook lockstitch
5. Rotating hook lockstitch
6. Double locking chainstitch

A very nice site to visit !

Should I mention that on the same parent site there is this amazing guitar tutorial !!

Efficiency of Sizing

Efficiency of Sizing Department

The major causes of loss of machine efficiency are:

1. Creeling, which includes removing the exhausted beams, mounting new beams, denting, leasing etc.
2. Replacement of weaver's beam on consumption

Efficiency in sizing

Let yarn count= 34
Set length on warper's beam= 18000 m
length of yarn on weavers beam= 1500m
Total number of ends= 4000
Full running speed= 50 m/min
No of lappers per 3000 ends per 1000 m = 3
Time to cut a lapper = 90 sec
Time to doff a beam and put new lease rods = 600 seconds
time to change a set = 6300 sec
Time loss/1000 m due to miscellaneous causes= 60 sec

Calculations

Sizing time of one beam with no stops : R = (1500x60)/50 = 1800 seconds
Lappers per beam of 1500 m per 4000 ends = 6
time lost in cuttin glappers per beam = 540 seconds
Number of weavers beam per set= 12
time lost per beam in a set change = 6300/12=525 seconds
time loss in beam doffing and leasing per beam = 600 seconds
Miscellaneous losses per beam of 1500 m = 90 sec
total time to size one beam = 3555 seconds
Machine efficiency = (1800 x 100)/3555 = 50.6%

Sizing Control points, sizing defects

Control of Yarn Stretch

During sizing, the yarns are under tension, this results in a slight permanent stretch in the yarn. It leads to a decrease in extensibility or elongation at break of the sized yarn, which leads to more breakage at the loom shed.

The various zones of stretch control on modern sizing machines are:

1. Creel zone: start- last warper beam, end-Dry nip
2. Wet Zone; Start- dry nip, end- first drying cylinder
3. Drying Zone: start- first drying cylinder, end- last drying cylinder
5. Splitting Zone: start-last drying cylinder, end- drag roll
6. Winding Zone: start- drag roll, end- loom beam

Control of Stretch in Creel Zone

The creel stretch on the existing type of sizing machines has to be controlled manually. The yarn tension in the creel zone increases gradually with reduction in diameter of the warper's beam. To counter this, the tightening of the beam is required to be adjusted suitably as the sizing progresses.

Control of Stretch in the Wet Zone

The control of stretch in this zone can be done with the help of 'positive dry nip'.

On multicylinder sizing machines, stretch can be controlled by synchronising the PIV gear during the cylinders with that driving he finishing squeeze roller in the wet zone.

Control of Moisture in sized yarns

A moisture control of 8-10% should be maintained in the sized cotton yarns. With excessive drying, the size film becomes brittle and harsh.
Very high moisture content is also undesirable because it makes the size films soft and the yarn sticky.

Quality of Sized Beams

A satisfactory weaver's beam should unwind well on the loom. These are some of the important package faults:

1. Density of sized beams: A loosly packed weaver's beam does not work well. The density is mainly influenced by two factors:
a. effectiveness of the friction clutch or the DC drive
b. effectiveness of the bream pressing motion.

2. Broken ends, missing ends, crossed ends, sticky ends

The major sources of all these faults are
a. lappers
b. invisible breaks during sizing

A lapper is an accumulaiton of layers of yarn on the warper's beam.

Those end breaks during sizing that do not form lappers are called invisible breaks.

Both lappers and invisible breaks result in missing and broken ends in the sized beams.

Crossed Ends- these are formed during weaving whenever the leading end is not available in the appropriate place on the beam,and, therefore, the weaver has to knot the trailing end to an end that is far away. This happens because in some cases the leading end of an invisible break migrates to a distant place.

Sticky ends - These are caused when broken ends from the warper's beam migrate to the yarn of another warper's beam.
In order to control these faults, it is necessary to control the incidence of lappers and invisible breaks.

Factors affecting lappers:
- End breakage rate at warping
- Efficiency of warp stop motion at warping
- condition of beam flanges (warper's)

Factors affecting invisible breaks
- High stretch at sizing
- weak places in the yarn

Defective selvedges

There are two types of defective selvedges that cause more difficulty in unwinding during weaving than the ends of the beam of thebeam. These are:
1. Sunken selvedges
2. Bulging selvedges

These defects can be controlled by
a. correctly setting the expandable comb at the headstock
b. Using the correct size of beam pressing roller so that it reaches both the beam flanges.
c. Ensuring that beam flanges are true.

Formation of ridges on the Beam

Ridges on the beam are formed when the ends that are taken in one dent of the comb do not spread out. To minimise the falut the eccentric dancing rollers at the headstock should be adjusted properly.

Control of Size Pick-up

Control of size pickup

For control on variation of size pick up , the two steps required are:

a. determination of average size pick up on the beam
b. Suitable adjustment in sizing conditions

a. Determination of average size pick-up

Example: The weight of sized yarn on a beam was found to be 82.5 lbs. The beam contains 1050 yards of warp, whose count before sizing was 50s cotton.If the number of ends in the warp is 3000, calculate the following:
a. The weight of size on the yarn
b. The % of size put on the yarn
c. The count of sized yarn

a. Weight of size on warp= weight of sized warp- weight of same length of unsized warp

Now weight of unsized warp= (No of ends x length of warp in yds)/(count of unsized yarn x 840)= (3000x1050)/(50x840) = 75 lbs

Therefore weight of size on warp = 82.5 -75 = 7.5 lbs

b. Percentage of size on warp = (wt of size x 100)/ wt of unsized warp

= (7.5x1000)/75 = 10%

c. Count of sized yarn = (No of ends of the warp x length of warp in yds)/(wt of lbs of warp x 840) = (3000x1050)/(82.5x840)= 45.5s cotton

b. Control on sizing condition

1. Viscosity of size paste in size box: Any variation in the concentration or temperature alters the viscosity of the paste which in turn affects both the level of size pick up and extent of penetration. Initially as the viscosity increases, the size pick-up also increases. But as the viscosity increases beyond a point, the size pick up is reduced.

2. Sqeezing pressure and condition of squeezing nip: The squeesing pressure determines the extent of penetration of the size paste between the fibres of the yarn and also of the removal of excess size paste and hence the level of the size pick up.

3. Speed of the sizing machine: Other sizing conditions remaining unchanged, the size pick up increases with increasing sizing speed and vice versa. This is because the time available to squeeze the surplus size from the yarn is less at high speeds.

4. Depth of immersion roller in size paste: the depth of immersion roller in the paste determines the duration for which the yarn remains immersed in the paste. this duration in turn influences both the level of size pick up and the extent of size penetration.

5. Level of size paste in the size box: Variation in the level of size paste is an important source of size pick-up variations both within and between beams.

6. Density of ends: When the density of ends is high, difficulties are encountered in obtaining adequate and uniform size penetration. Therefore size pick up may vary at these fabrics.

Choice of Size Receipe

Choice of Size Receipe

The suitability of size receipe for the type of yarn should take into account, fabric construction, and end use as follows:

1. Cotton Yarn- Starch Based
Polyester etc.- Polyvinyl Alcohol (PVA) based

2. Fine and Superfine cotton- thin boiling Starches
Coarse Count- ordinary starch

3. Heavy Fabrics- Modified starches
Light and Medium- Ordinary starches

4. conventional sizing Machines- Low viscosity starch
High speed sizing machines- High viscosity starches

5. Unlbleached calendered sort of fabrics- More weighting agents, antiseptic softners etc. are used.
Bleached sorts- ordinary starches

6. Finer Counts and Heavier Constructions- More size pickups
Coarse counts- Less size pickups

7. Plied yarns- low size pick up or nil even

Ingredients for water Based Sizes

1. Adhesives- Potato starch, starch from cereals ( corn, wheat, rice etc0, carboxy methyl cellulose (CMC), Polyviny alcohol (PVA), Polyviny Chloride (PVC)

2. Lubricants- Mineral Waxes, vegetable waxes, animal fats, mineral oils, vegetable oils

3. Additives- Salicylic Acid, Zinc Chloride, Chloride emulsifiers.

Suggested Size Receipe

Ordinary starch=100
Gum= 2
Mutton tallow= 7.5

Preparation of Size Receipe

1. Ingredients

Water= 18.5"
Modified Starch = 50 kg
CMC= 5 kg
PVA= 10 kg
Gum = 1.5 kg
Softner= 1.2 kg
Antistat= 0.8 kg

Mixing: Took 17" water. Added Starch, Gum, CMC and PVA slowly and one by one as the slurry is stirred. Softner and antistat added in storage kettle.

Cooking

1. cold stirring at 50 rpm = 12 min
2. Transfer into pressure cooker through sieve=== 45 deg C
3. Stirrer rpm in cooker== 55
4. Close lid, open steam inlet, open air vent
5. Close air vent valve when steam is seen escaping through it, temperature = 96 deg C, Pressure = 10 PSI
6. time between point 3 and 4 == 15 min
7. Cooking starts, steam continued till temperature = 130 deg c, Pressure = 40 PSI
8. Time for getting 130 deg C after closing air vent valve = 25 min
9. Stem in-let closed
10. 10 minutes after closing steam, Temp= 124 deg C, Pressure = 32 PSI
11. Total cooking time after getting 130 deg C= 35 min
12. Flow time of paste taken through sample valve= 24 seconds
13. Transferred to storage beck
14. Final volume = 18.5 "
15. Stirrer RPM in storage beck = 20
16. Temperature after 10 min. of transfer = 100 deg C
17. Refrectometer reading= 16

Lab Data

1. Size add on = 18 %
2. Increase in strength % = 5.2
3. Elongation at break % os sized yarn = 6.8%

Process Control in Sizing-1

Sizing

The process consists of laying warp yarn parallel and sizing the yarn with a mixture to strengthen it to withstand the rigours of weaving.

Warp yarn is withdrawn in sheet from from warp beams which are placed at the back of the sizing machine. The yarn is then passed through sow box. Size solution is applied by immersion. After removing surplus solution that occurs at this state, the yarn is dried and arranged on a loom beam.

The objective of sizing is RESISTANCE to ABRASION

This objective is achieved by applying on the yarn a unifrom and smooth protective film of suitable sizing material.

We also want that in the sized yarn there should be

- Some increase in tensile strength in the yarn
- Minimum loss of extensibility in yarn ( about 4.4-4.6% elongation at break is required for cotton)
-Required moisture content ( 8-10% of cotton)
- Good quality of sized beam (neither too soft nor too firm + free from yarn defects)
- Good productivity and efficiency
- Reduced Cost

Process Control in Sizing

The process control programme in sizing should, therefore, comprise of the following aspects:

1. Selecting the correct size receipe and size pick -up level
2. Ensuring correct preparatio of size paste
3. Control of
- size pick up
- stretch
-moisture content
-quality of beam
-machine speed
-machine efficiency
-a method to calculate the expected level of productivity

Cost of Warping

Warping process is required exclusively for preparing warp yarn for weaving. Hence warping cost should be calculated for warp yarn.

Unit costs in this section can be developed on weight basis or on length basis.

Weight Basis

Warping cost per piece length of fabric= weight of warp yarn per length x cost per unit weight.

If unit costs are developed on length basis, they are expressed with reference to specific number of ends (generally 400-500 ends). It follows , therefore, that about four to eight beams ( some time even more) would be required to made one beam for weaving.

In other words, unit cost in terms of length will have to be multiplied by the number of warp beams required per weaving beam. Then warping cost per piece length of a fabric can be calculated as shown:

warping cost per piece length of fabric = cost per meter x tape length x no of warp beams per weaving beam.

If the warp beam is partly colored and partly greige, warping cost should be calculated for greige warp yarn and coloured warp yarn. Generally coloured yarn is processed on slow speed warping frame. Hence cost of color warping usually works out higher as compared to the cost of greige warping.

control of end breaks in warping

Minimising end breaks in warping involves four steps namely:

1. Control of tension in the yarn
2. Satisfactory maintenance of those machines
3. Minimising the defects on packages produced at winding
4. A regular check on the end breakage rate for comparison with the norm.

1. conrol of tension in the yarn

On the warping machine, there are two types of variation in yarn tension
1. Between different stages of unwinding of a package. This can be detected after the first thread guide.
2. Between ends. It can be detected at the head stock.

The tension variation that occurs during the unwinding of a package can be minimised if you design the creel such that the distance between the package and the first thread guide is shortest, it will avoid the yarn balloon rubbing the nose of the package.

The tension variation between the ends at the headstock is minimised if the groups of neighbouring ends on the beam are taken from the same column of packages in the creel.

2. Condition of Machine

a. Alignment of the package at the creel

Non alignment of the creel package with respect to the first guide is often seen to be a cause of high end breakage rate at warping. This alignment is done with the help of a gauge.

b. Eccentric Guide rollers

On machines with mechanical stop motions, there are several guide rollers at the headstock which are positioned very near to one another. Eccentricity in those rollers can introduce short term tension variations of high amplitude.

c. Thread Guides

Deep cuts in thread guides can significantly increase yarn tension and hence deteriorate warping performance. If found dirty, the thread guides should be cleaned with CCl4.

d. Relative humidity and temperature

For satisfactory working at warping, about 60% RH should be maintained. The dry bulb temperature should be kept at about 29 o C (84 o F). Lower humidity may increase yarn hairiness, end breaks and liberation of fluff. The fluff ultimately passes to the beam and given difficulty during sizing. Higher humidity is unnecessary; in fact relative humidity higher than 70% may increase end breakage rate.

Process Control in Warping-3

Process Control in Warping-3

Maintenance Check points at Warping

Machine

1. Clean with compressed air at every creel change-per shift
2. Clean with compressed air and cleaning waste- weekly

Package Alignment at the Creel

1. Look for incorrectly aligned packages, correct if the non-alignment is too severe- regularly
2. completely guage the creel with the help of a gauge- half yearly

Tension Weights

In case of high speed warping machine, check tension weights at every count change- regularly

Tension Level

Check the tension levels with tension meter- Monthly

Stop Motion and Brake

1. Ensure that the machine stops within 1 1/2 revolutions fo the drum in case of high speed warping- regularly
2. Check with condition of drop pins and replace those with cut marks- regularly.

Guide rollers

1. Check for concentricity- half yearly

Beams
1. Check for the conditions of flanges and beam shafts, repair damaged beams- regularly

Creel Fans
1. Check that creel fans oscillate properly and are not chocked with fluff- regularly.

Parts in yarn path

1. Check for cuts in parts of machine in yarns parts regularly.
2. repair/replace the parts with cut marks- weekly

Process control in warping-2

Efficiency of Warping Department

The following will calculate the efficiency of a warping machine:

Let Speed in m/min= 300
Set length (m) = 18000
Yarn length on cone/cheese (m)= 54000
Number of Ends/beam= 500
end breaks/400 ends/ 1000 m = 3
Time to mend a warp break (seconds) = 35
Time to change a beam (seconds) = 500
Time to change a creel (seconds) = 3000
Time loss due to miscellaneous causes/1000 m (seconds)= 25

Calculation

Running time R (s) = 1000x60/300 = 200
R is the uninterrupted running time in meters
Breaks/running ends in beam/1000 m = 3x500/400 = 3.75
Stoppage time /1000 m
(a) to mend breaks (s)= 3.75x35 =131 s
(b) to change a beam (seconds) = 500x1000/18000 = 28 s
(c) to change a creel = 3000x1000/54000 = 56 sec
(d) Miscellaneous time = 25 seconds

Therefore, S, the total stoppage time per 1000 meters (s)= 131+28+56+25 = 240 s

Therefore total efficiency = Rx100/(R+S)= 200x100(200+240) = 45.5 %

Expected Production per shift of 8 hours (m) = (300x60x8x45.5)/100 = 65,500 m

Causes of Low efficiency or Low productivity

1. Increase in End breakage rate

The machine efficiency at warping is highly sensitive to the end breakage rate

2. Improper utilisation of magazine creel

If the creel boy does not keep the magazine creel ready to be used by the time the package in the running creel are over, the efficiency will fall.

3. Reduction in Average Set-length

Lower set lengths reduce the machine efficeincy at warping

4. Number of Tenters per Machine

The number of tenters per machine determine the time to mend an end break. This is because by the time the warper finds a broken end on the beam, the creel boy brings the other end of the broken yarn from the creel

5. Stops due to Machine Breakdown, shortage of cones etc.

If the stops due to machine breakdown, shortage of empty beams or cones/cheeses etc. are high, the actual efficiency of the machine will be lower than calculated.

Process Control in Warping-1

Process Control in Warping

Warping is the process of winding together on a beam a specified number of warp ends from Creel. The creel is a convenient rack for holding spools, cones or cheeses while the yarn is withdrawn to the warp beam.

The following are the process control parameters in a warping department:

1. Minimising End breaks.
2. Quality of warping beam
3. Control of productivity

Importance of Minimising end breaks:

The stoppage of the machine due to an end break is likely to deteriorate the quality of the beam due to three reasons:

1. The rubbing of the beam by the drum which stops abruptly.
2. Owing to the difficulty in finding the broken end, there is a possibility of incorrect mending. It may lead to lappers during sizing.
3. There is some loss in the extensibility of broken end when the machine is stopped, it increases the probability of breakage in weaving and sizing.

The following points should be noted to improve the quality of warping beams:

1. condition of beam flanges:

If the beam flanges are damaged, the unwinding of yarn near the flanges will not be satisfactory. This will cause difficulties in sizing and weaving.

2. Stop Motions and Breaks:

Proper stopping of the warping machine after an end break ensures that the broken end on the beam can be traced easily.

3. condition of the driving drum:

On most warping machines the beam is driven by fricitonal contact with the driving drum. In order to get a package of the correct density, the pressure between the drum and the warper's beam has to be kept at fairly high level.

4. Barrel Diameter of the Beam

Beams of small barrel diameter give rise to high unwinding tension at sizing, particularly when the beam is about to become empty.

5. Cuts in Accessories in the path of yarn

Drop pins of stop motion, guide rollers, reed denting etc. should bot have any grooves.

6. Creel Fans

Fluff accumulated on the machine, particularly at thread guides, causes tension variations in the yarn. This fluff can pass on to the beam.

7. Length Measuring Motion

The length measuring motion should be accurate, otherwise estimation of beam count would be wrong and subsequently will give incorrect values of size percent which is commonly determined from the weights of yarns on the warper's and the size beams.

8. Density of the Beam

The beam should be firm, inadequate pressure between the beam and the drum causes soft beam. Adequate pressure should be maintained by making suitable mechanical adjustments.

Control of Productivity

The productivity at warping depends upon the machine efficiency and machine speeds. The speed is governed by the mechanical condition of the machine and its design. Machine efficiency depends on several factors, such as the breakage rate, the time taken to mend the machine stop, set length, length of yarn on supply package etc.

FAQ in cotton Spinning-11

Q: Why cotton system of spinning is called so ?
Ans: Because it was initially developed for spinning cotton fibres.

Q: How fiber length affects spinning ?
Ans: A longer fiber can be spun to a finer counts and gives a better spinning performance. In general, the longer the fiber, the higher the yarn tenacity. Too long a fiber gives processing problems specially in carding. Productivity also increases because the yarn spun from a longer fiber needs a lower twist.

Q: What should be the min. number of fibres in the yarn cross section for better spinning performance.
Ans: It should be around 85 for 38 mm and 68 for 51mm fibre

Q: How finer fiber affects spinning performance.
Ans: A fiber fiber can allow spinning of finer yarns. It also leads to more even yarns. Also low twist is required because of greater interfiber friction. However it can lead to excessive neps at carding.

Q: How finer fiber affects the fabric.
Ans: Fabrics produced from finer fibers drape better. They also have a soft "sheen". It usually produces softer fabrics.

Q: What is the formula to calculate the number of fibres in a yarn cross section.
Ans: N = (5315/fiber denier)/ yarn count (Ne)

Q: What is the min fiber strength needed for spinning ?
Ans:0.6 to 0.7 grams/denier

Q: What is crimp. How does it affect spinning.
Ans: It is defined as the weaviness of a fiber. It increases the interfiber friction which helps in spinning process. It also produces yarns and fabrics haveing a greater bulk and a softer feel.

Q: How crimp is measured.
Ans: Crimp is measured in arcs/inch

Q: What will happen if crimp is lower? If crimp is higher ?
Ans: A lower level of crimp than recommended can lead to problems such as  lap licking, higher cylinder loading, card web breaking and roller lapping. A higher level of crimp will lead to excessive neps.

Dyeing Hints

This site talks about very practical dyeing hints. Some of which are "animals are acidic and botanicals are basic", how to measure mordants and dyestuff, besides dyeing terminology.

FAQ in Cotton spinning-10

Q: what is the object of aprons.
Answer: The object of aprons is to contol the floating fibres to the possible extent and help to produce regular and stronger yarns with greater drafts.

Q. What is the importance of gap between the two aprons.
Answer: The aprons are not be too far apart or too close. Wider gap fails to control the floating fibre movement. If the gap is less, the pressure between the aprons more. The front-roller-gripped fibres suffer undue strain and the result is the formation of the defect known as 'crackers'

Q. What are the top roller cots or coverings. What is their importance.
Ans: the top rollers of draw frames, speed frames and ring frames, are made of metals. These are usually covered with a convenient cushioning material called as cots.

Q. What is the importance of the top roller cots.
Ans: These are needed to avoid the fibres getting crushed or damages, and also to give a proper grip on the fibres when they are being drafted.

Q. What are the requirements of a good cot.
Ans: A good cot is expected to have unifrom quality and performance, capable of being buffed to precise limits. It should have anti-lap up, oil-resistant, antistatic, trouble-free and temperature properties. It must possess good resilience in order to provide the required degree of cushion and must not contribute to end breaks.  It should withstand channeling action and any tendency for flute marding when top rollers are left standing under weight or pressure.

Q. What is the hardness of the cot. what is its importance.
Ans: A shore hardness of 60 deg to 90 deg is preferred. A harder surface would give rise to greater roller slip. A softer surface will lead to more roller lapping.

Q. Why top roll surfaces are grooved.
Ans: The object of grooving is to minimise the lap-up tendency, besides reduction of fly accumulation on top cleaners. The grooving also prevents surface distortions.

Q. What is the object of roller weighting.
Ans: In any pair or rollers, the bottom roller is positively driven while top roller is driven with the grip of the bottom roller. Normally the top rollers themselves fail to exert sufficient pressure and have to be assisted by some suitable external devices. Such devices are known as "roller-weighting devices"

Q. What is roller setting ? What is its importance ?
Ans: The distance between the centres of two pairs of rollers is called roller setting. If the pairs of rollers are set too wide apart, there will be plucking of the fibres instead of even attenuation, and the material that comes forward is full of thick and thin portions. On the other hand, if they are set too close, drafting becomes difficult and many of the long fibres get gripped by both the pairs momentarily. The fibres get either damaged or broken.

FAQ in cotton Spinning-9

FAQs in Cotton Spinning

Q. What are the objects of ring spinning
Answer: There are three objects of ring spinning:
1. To draw the roving to the desired degree of fineness.
2. To impart sufficient twist to the emerging strand of fibres to from continuous yarn
3. To wind up the spun yarn into some convenient package form.

Q. What is the object of twist in Ring frame
Ans: The object of twist is to form a yarn with sufficient strength.

Q. Why every spinner wants to produce a yarn with as low twist as possible
Ans: Imparting twist consumes power, it also leads to low production. Also in untwisted from strength of yarn is about 30% more than in twisted state. Cloth manufactured bya low twist yarn tends to be fuller, stronger and more durable, Also dye absorption is better in low twisted yarns.

Q. How fiber length is related to twist
Ans: Longer the fiber, lesser is the amount of twist required. Frictional force increases with greater fibre length and as such there is more clinging power.

Q. How is fiber diameter is related to twist.
Answer: finer the fiber, more is the surface area available for clinging, thus more is the clinging power, hence lesser is the amount of twist required.

Q. How yarn diameter is related to twist ?
Ans: Coarser the yarn, more are the number of fibres per cross section and thus lesser is the required twist.

Q. How twist is related to yarn contraction ?
Ans: When twisted, the fibres take helical shape, that is, they get bent. Owing to this bending, there is a reduction in the length actually delivered from the front roller nip. This reduction in length is called contraction.

Q. What are the directions of twist ?
Ans: There are two popular ways in which yarn is twisted. Right Hand Twist is formed when the spindle revolves in clockwise direction as viewed from top. RH twist is also called, warp way, Z-way or twist way. The Left Hand twist is fromed when the spindle revolves in Anti clock wise direction. LHT is also called weft-way, S-way, reverse way etc.

Q. What are the various conventions of twist directions used in cloth.
Answer: A cloth is supposed to be best if woven with warp twisted right way and weft twisted left way.

Q. Why we avoid S-twist on ring frames.
Ans: It is often difficult to get left hand piecers to attend the machine with S-way twisting.

Q. Why over twisted yarn is not preferred ?
Answer: When overtwisted, the yarn becomes unbalanced. The yarn contracts excessively and becomes poor in strength. the yarn becomes hard, stiff and wiry. It has a harsh feel and dull appearance. It caused a lot of trouble in weaving.

Q. Why overtwisted yarns sometimes are needed.
Ans: Overtwisted yarns are manufactured for some special purpose. 'crepes' and 'voils' are woven with overtwisted yarns.

FAQ in cotton spinning-8

Comber

Q. What is a comber
Answer: Comber is a machine where short fibres below a certain predetermined length can be easily separated out.

Q. What are the objects of combing
Ans: After combing the fibres are more or less uniform, well straightened or parallelised and free of neps and particles of trash that escaped carding.

Q. What will happen if carded material is presented as such to comber.
Ans: Majority of the fibre hooks in a carded sliver are trailing. Hooks can be straightened out by comber needles provided they are presented in leading position. If the trailing hooks are presented as such, they behave like short fibres and escape into noil.

Q. How we can make majority hooks (trailing) from card sliver to present as leading hooks to comber.
Ans: In order to make the major hooks take the leading position, there should be even passages or even reversals between the card and the comber.

Q. What is lap preparation for comber
Ans: 'Lap preparation' can be taken as a general term which includes all the passages between the card and the comber.

Q. What is backward feed
Ans: On conventional combers the feed usually takes place when the nippers are going backwards. This is known as backward feed.

FAQ in Cotton Spinning-7

Q: What is the object of a speed frame
Ans: The object of a speed frame process is to reduce the sliver bulk to a diameter suitable enough fro the ring spinning frame to spin yarn.

Q : Why twist is required at the speed frame
Answer: Minimum twist is required to see that 1. The roving comes from the front roller nip on to bobbin through the flyer bore without being broken. b. The roving is nicely wound on to the bobbin. 3. that it does not suffer any creel stretch during unwinding in the next machine creel.
4. that the next machine can easily break the twist in the break draft zone.

Q. What is the function of paddle.
Ans: the paddle helps to produce compact and regularly built bobbins.

Q. How come the paddle always keeps pressed against the bobbin.
Answer: The paddle always keeps pressed against the bobbin due to the centrifugal force of the vertical solid bar.

Q. Why the threading slot is in the curved form.
Answer: This helps to prevent air drafts from entering the tube and disturbing the roving inside it. Besides it prevents liberation of fly.

Q: What causes winding of the twisted roving on the bobbin.
Ans: The differential surface speed between presser paddle and bobbin surface are responsible for winding of the twisted roving on the bobbin. Which is caused by differences in the flyer speed and bobbin speed.

Q: Why bobbin speed is reduced as the package diameter increases
Ans: As the diameter grows, bobbin surface speed increases although the revolutions per minute is constant. Therefore, bobbin speed is reduced in order to maintain the constant difference between the speeds of bobbin surface and paddle.

Q: What is 'flyer leading' and 'bobbin leading' case. Which is used in existing Speed frames.
Answer: S/F in which the flyer speed is higher than the bobbin surface speed is called 'flyer leading'. S/F in which the bobbin speed is higher than the flyer speed is called 'bobbin leading'. 'Bobbin Leading' case is used in existing S/F.

FAQ in Cotton Spinning -6

FAQ in Cotton Spinning-6

Q. What type of hooks are there in the card web ?
Answer: Bulk of the fibres in the card web are found to have hooks at their rear ends, and they are termed as trailing hooks.

Q. What type of hooks are removed at the drawframes.
Answer: Hooks are preferentially removed when they are presented in the drafting field in trailing direction.

Q. What is doubling. How does this affect regularity of a sliver.
Answer: Doubling is feeding more slivers together into the drafting zone. It improves the uniformity of sliver.

Q. Why we cannot offer a high draft in one go.
Ans: The resistance offered by the disorderly state often results in a greater unevenness in the drawing material.

Q. What can be the drawbacks of excessive parallelisation.
Ans: Slivers with high parallelisation become soft and their withdrawl from cans at later stages results in excessive creel breakages.

Q. What is roller slip
Ans: Top rollers are no positively driven. They are made to bear against the bottom fluted rollers with a suitable weighting arrangement. The motion transmission to the top roller is through the bulky sheet of fibres. Thus the speed of top roll is not the same as botton roll. This fall in speed of top roller is termed as roller slip.

Q. what will happen due to roller slip
Answer: The roller slip produces characteristic drafting waves or unevenness characeristics.

Q. What is a drafting wave
Answer: The irregular motion of short fibres between pairs of rollers give rise to a wave like formation that is known as drafting wave.

Q. What is the principle applied in roller setting over 44 drafting system.
Answer:
Front and second pair= effective length + 1/8 "
2nd and Third pair= eL+ 1/8"+1/8"
3rd and Back Pair= eL+1/8"+1/8"+1/8"

FAQ in cotton spinning-5

FAQ in Cotton Spinning-5

Question: What is the function of calender rollers.
Answer: The function of calender rollers primarily is:
a. To draw the web away from the doffer at a uniform rate as fast as it is stripped.
b. It exerts sufficient pressure on the sliver in order to reduce the bulkiness of this sliver.

Question: How diameter of trumpet hole varies with the thickness of the sliver.
Answer:

Diameter of hole in inches= constant x sqrt (grains/yard of sliver)

constant= 0.022

Question : How does the setting to the following pair of card points affect the quality of sliver produced.
Answer:
Taker in to cylinder: wider settings: creates neps and licker-in gets covered with fibres.
Back Plate to cylinder: wider setting causes fly to blow between flats.
Flats to cylinder: Closer settings gives better quality.
Front Plate to cylinder: closer setting-> reduces the weight of flat strip. wider setting-> results in heavier flat strips.
Doffer to cylinder: wider settings-> creates more neps as fibres go round the cylinder unnecessarily more times.
Feed plate to Licker in : wider settings-> lap is plucked without sufficient opening. So web quality is reduced.

Question: What are different types of carding wastes and their constituents
Answer: Licker- in waste-> short fibres, trash.
Flat Strips-> cotton fibres (short)
Stripping waste ( on cylinder and doffer wire)-> short fibres and trash

Question: Why flexible wire clothing is preferred over metallic wire clothing for running long fibres.
Answer: It is observed that flexible fillet has a more gentle carding action and gives lesser damage to good fibres.

Question: Why draw frame is needed
Answer: The fibres in a card web lie haphazardly criss cross to the web. Besides, fibres have either one or both end bent into the form of hooks. These haphazard fibres are required to be straightened and parallelised to the possible extent, also evenness and regularity of sliver is improved.

Process Control in Cotton Mixing- Part 1

How Cotton Mills Select Bales: Cotton Mix Profile, Population Profile and Bale Picking Explained with a Simple Example

Cotton mixing is one of the most important decisions in spinning. Many people think that a mill buys cotton, opens the bales, mixes them, and starts spinning yarn. In reality, good spinning mills do not mix cotton casually. They create a cotton mix profile, study the population profile of available bales, and then use a bale picking scheme to ensure consistency in yarn quality and processing performance.

The central message is simple: cotton should not be selected only on the basis of price. It should be selected on the basis of fibre properties, yarn requirements, processing performance, variability, and cost together. A cheaper cotton bale may look attractive at the purchase stage, but it may create higher hidden costs during spinning, winding, weaving, knitting, or finishing.

Table of Contents

• 1. Why Cotton Mixing Matters
• 2. What Is a Cotton Mix Profile?
• 3. Fibre-to-Yarn Thinking
• 4. Denim Yarn and Knit Yarn Need Different Cotton
• 5. What Is Population Profile Analysis?
• 6. Why Random Bale Picking Can Be Risky
• 7. Grouping and Categorization of Cotton Bales
• 8. A Simple Hypothetical Example
• 9. Method 1: Random Picking
• 10. Method 2: Proportional Weight Category Picking
• 11. Method 3: Optimum Category Picking
• 12. Adding Cost to the Problem
• 13. Final Comparison of Picking Methods
• 14. Practical Meaning for a Spinning Mill
• 15. Related Reading
• 16. Conclusion
• 17. General Disclaimer

1. Why Cotton Mixing Matters

Cotton is a natural fibre. No two bales are exactly the same. One bale may have higher fibre strength, another may have more short fibres, a third may have higher micronaire, and another may have more neps or trash. These differences directly affect yarn quality and processing behaviour.

A poor cotton mix can lead to lower yarn strength, more end breakages, higher hairiness, more imperfections, more fly generation, poor weaving or knitting performance, higher waste, and higher hidden manufacturing cost. This is why the lowest-priced cotton is not always the cheapest cotton in real terms.

Visual 1: Cotton bale selection map connecting fibre properties with yarn quality and processing performance.

2. What Is a Cotton Mix Profile?

A cotton mix profile is the desired fibre-property profile required for a particular yarn. Before deciding the cotton mix, the mill must first ask what yarn is being made. The required cotton will depend on the spinning system, yarn preparation, yarn count, twist level, yarn quality requirement, end product, cotton price, and yarn selling price.

For example, cotton required for coarse denim yarn will not be the same as cotton required for fine knitwear yarn. Denim yarn may demand strength and weaving performance, while knit yarn may demand softness, flexibility, low hairiness, low fly generation, and good dimensional stability.

An optimum cotton mix is therefore not merely a cheap mix. It is a bale laydown that provides the desired yarn characteristics, good processing performance, and lowest possible total cost.

3. Fibre-to-Yarn Thinking

This leads to the idea of fibre-to-yarn modelling. This means understanding how fibre properties influence yarn properties. It is a practical way of connecting raw material decisions with final yarn behaviour.

Forward Projection

Forward projection asks: if I use cotton with these fibre properties, what yarn quality will I get? For example, micronaire, fibre length, fibre strength, and short fibre content may influence yarn strength, hairiness, imperfections, and processing performance.

This relationship may be represented as:

\[ \text{Fibre Properties} \rightarrow \text{Yarn Quality and Processing Performance} \]

Backward Projection

Backward projection asks: if I want this yarn quality, what fibre properties should I choose? For example, if the mill wants a soft, low-hairiness knit yarn, it must select fibre properties that help achieve that goal.

This can be represented as:

\[ \text{Required Yarn Quality} \rightarrow \text{Required Fibre Properties} \]

This is very close to modern predictive modelling. Today, we may use regression, machine learning, optimization, or simulation, but the basic textile logic remains the same.

4. Denim Yarn and Knit Yarn Need Different Cotton

Denim Yarn

For denim yarn, the important factors are yarn strength, spinning ends-down, rope beaming efficiency, and weaving performance. The important fibre properties include micronaire, fibre strength, short fibre content, variability in fibre strength, and variability in micronaire.

In denim production, rope beaming is especially important. If the yarn has high hairiness, weak places, or excessive splices, rope beaming efficiency may suffer badly. So for denim, the cotton mix must support strength, weaving performance, and processing efficiency.

Knit Yarn

For knit yarn, the priorities are different. Important parameters include yarn strength, twist, hairiness, imperfections, fly generation, softness, flexibility, and dimensional stability.

Knit yarn should usually be soft. So twist cannot be too high. But if twist is too low, the yarn may lose strength and integrity. Therefore, knit yarn requires a balance between enough twist for strength and low enough twist for softness.

This balance may be expressed as:

\[ \text{Optimum Twist} = \text{Sufficient Strength} + \text{Required Softness} \]

Longer, stronger, and finer fibres help achieve this balance. Short fibre content and neps are especially damaging in fine knit yarns because they increase imperfections and fly generation.

5. What Is Population Profile Analysis?

After deciding the desired cotton mix profile, the next question is whether the bales available in the warehouse match this requirement. This is called population profile analysis.

The bale population is studied using three main parameters: population size, average value of fibre attributes, and variability of fibre attributes. For example, suppose a warehouse has 2,000 cotton bales. Their micronaire values may have a mean of 4.0 and a standard deviation of 0.8.

The selected cotton laydown should be representative of the population, unless there is a deliberate reason to modify it. Ideally, the cotton mix should match the population in terms of mean value, within-mix variance, and controlled between-mix variation.

In simple language, this means every laydown should be consistent. One laydown should not be very different from another laydown, because that difference will later appear as variation in yarn and fabric performance.

Visual 2: Population profile of cotton bales showing mean, variation and selected laydown.

6. Why Random Bale Picking Can Be Risky

In random bale picking, bales are selected randomly from the warehouse. This may sound fair, but it can create inconsistency. One laydown may accidentally get more high-micronaire bales, while another may get more low-micronaire bales.

Random bale picking works better when the total bale population is already very uniform and the number of bales in each laydown is large. But if the warehouse has high variability, random selection can create unstable results.

7. Grouping and Categorization of Cotton Bales

Grouping

Grouping means dividing cotton bales into broad groups. For example, the mill may create separate groups for denim yarn, knit yarn, low-quality cotton, high-quality cotton, cotton from different regions, or cotton for different spinning systems.

If a mill produces both denim yarn and knit yarn, it should not blindly pick cotton from one common pool. Each yarn style needs its own cotton population.

Categorization

Categorization means dividing bales within a group based on fibre-property ranges. Bales may be categorized by micronaire, fibre length, fibre strength, short fibre content, or other important fibre attributes.

Suppose we use two fibre properties: micronaire and fibre length. If each property is divided into three categories, then total combinations are:

\[ 3^2 = 9 \]

If three properties are used, such as micronaire, fibre length, and fibre strength, then:

\[ 3^3 = 27 \]

So the number of combinations increases rapidly. This is why modern cotton mixing requires systematic data handling.

8. A Simple Hypothetical Example

Let us take a small example. A spinning mill has 100 cotton bales in the warehouse. The mill wants to prepare a 20-bale laydown. We will use only one fibre property: micronaire.

Category	Micronaire Range	Number of Bales	Average Micronaire
A	Low Mic	30	3.5
B	Medium Mic	50	4.0
C	High Mic	20	4.5

The warehouse average micronaire is:

\[ \frac{(30 \times 3.5) + (50 \times 4.0) + (20 \times 4.5)}{100} \]

\[ = \frac{105 + 200 + 90}{100} \]

\[ = 3.95 \]

So the target population average is 3.95. The mill wants every 20-bale laydown to remain close to this value.

9. Method 1: Random Picking

Suppose the mill randomly picks 20 bales. One random laydown may contain 5 bales from category A, 8 bales from category B, and 7 bales from category C.

Category	Bales Selected
A	5
B	8
C	7

Average micronaire:

\[ \frac{(5 \times 3.5) + (8 \times 4.0) + (7 \times 4.5)}{20} = \frac{17.5 + 32 + 31.5}{20} = 4.05 \]

This laydown has average micronaire of 4.05, which is higher than the target of 3.95. Another random laydown may contain 9 bales from A, 9 bales from B, and 2 bales from C.

\[ \frac{(9 \times 3.5) + (9 \times 4.0) + (2 \times 4.5)}{20} = \frac{31.5 + 36 + 9}{20} = 3.825 \]

Now the average is lower than the target. So random picking may create different laydowns with different fibre profiles.

Laydown	A Bales	B Bales	C Bales	Average Micronaire
Random Laydown 1	5	8	7	4.05
Random Laydown 2	9	9	2	3.825

This variation may later appear as variation in yarn quality.

10. Method 2: Proportional Weight Category Picking

Now let us use Proportional Weight Category Picking, also called PWC. In this method, bales are selected from each category in proportion to their presence in the warehouse.

Category	Number of Bales	Percentage
A	30	30%
B	50	50%
C	20	20%

The laydown size is 20 bales. So we select:

\[ A = 30\% \times 20 = 6 \]

\[ B = 50\% \times 20 = 10 \]

\[ C = 20\% \times 20 = 4 \]

Category	Bales Selected
A	6
B	10
C	4

Average micronaire:

\[ \frac{(6 \times 3.5) + (10 \times 4.0) + (4 \times 4.5)}{20} = \frac{21 + 40 + 18}{20} = 3.95 \]

This exactly matches the warehouse average. So PWC gives a much more stable laydown than random picking.

11. Method 3: Optimum Category Picking

Now suppose the mill wants to reduce variation even further. Let us assume the categories have different internal variation.

Category	Average Micronaire	Standard Deviation
A	3.5	0.20
B	4.0	0.10
C	4.5	0.20

Category B is more uniform because its standard deviation is lower. An optimum category picking method may select slightly more bales from B while still keeping the average micronaire close to the target.

Category	Bales Selected
A	5
B	12
C	3

Average micronaire:

\[ \frac{(5 \times 3.5) + (12 \times 4.0) + (3 \times 4.5)}{20} = \frac{17.5 + 48 + 13.5}{20} = 3.95 \]

This also gives the same target average of 3.95, but it uses more bales from the most uniform category. So both PWC and OPC may hit the target mean, but OPC can reduce laydown variation further.

Method	A Bales	B Bales	C Bales	Average Micronaire
PWC	6	10	4	3.95
OPC	5	12	3	3.95

Visual 3: Comparison of random picking, proportional category picking and optimum category picking.

12. Adding Cost to the Problem

Now let us add cotton cost. This makes the problem more realistic because mills must balance both quality and cost.

Category	Average Micronaire	Cost per Bale
A	3.5	₹45,000
B	4.0	₹48,000
C	4.5	₹44,000

Category C is the cheapest. A purchase manager may be tempted to use more C bales. Suppose a cost-biased laydown uses 6 bales from A, 7 bales from B, and 7 bales from C.

Average micronaire:

\[ \frac{(6 \times 3.5) + (7 \times 4.0) + (7 \times 4.5)}{20} = \frac{21 + 28 + 31.5}{20} = 4.025 \]

The average micronaire shifts upward from 3.95 to 4.025. Now compare the cost.

PWC Cost

\[ (6 \times 45000) + (10 \times 48000) + (4 \times 44000) \]

\[= 270000 + 480000 + 176000 = \text{Rs. } 926000\]

Cost-Biased Mix Cost

\[ (6 \times 45000) + (7 \times 48000) + (7 \times 44000) \]

\[ = 270000 + 336000 + 308000 = \text{Rs.} 9,14,000 \]

The saving is:

\[ 9,26,000 - 9,14,000 = 12,000 \]

At first glance, this looks attractive. But if the higher micronaire causes harsher yarn, more fly, more hairiness, more processing breaks, or poorer fabric quality, then this saving may disappear. This is the key lesson: the cheapest cotton mix is not necessarily the most economical cotton mix.

13. Final Comparison of Picking Methods

Method	Logic	Average Micronaire	Cost Control	Quality Risk
Random Picking	Pick any 20 bales randomly	May vary	Uncontrolled	High
PWC	Pick according to population proportion	Stable	Moderate	Low
OPC	Pick to reduce variation	Stable	Can be optimized	Lowest
Cost-Biased Picking	Pick more cheaper bales	May shift	High short-term saving	Possible hidden risk

It can be showed that random picking gives much higher between-laydown variation than proportional or optimum category picking. In the comparison shown there, random picking had the highest between-laydown variance, while PWC and OPC reduced this variation substantially.

14. Practical Meaning for a Spinning Mill

A spinning mill should not simply ask which cotton is cheapest. It should ask which combination of bales gives the required fibre profile with minimum variation and acceptable cost.

This question combines textile science, statistics, and cost optimization. A good bale selection system should ensure that the average fibre values are close to target, variation within the laydown is controlled, variation between laydowns is minimized, the cotton mix suits the yarn and fabric end use, and the cost is optimized without damaging process performance.

15. Related Reading

Related Reading on Cotton, Yarn Quality and Spinning Decisions

• Understanding Cotton Fibre Properties and Their Effect on Yarn Quality
• Micronaire in Cotton: Meaning, Importance and Practical Interpretation
• Yarn Count, Twist and Fibre Selection in Spinning
• How Short Fibre Content Affects Spinning Performance
• Building a Python Model for Cotton Mixing Decisions

16. Conclusion

Cotton mixing is a scientific decision. It begins with understanding the yarn requirement, continues with defining the cotton mix profile, then studying the bale population, and finally selecting bales through a suitable picking scheme.

Random picking may be simple, but it can create unstable yarn quality. Proportional category picking gives better consistency. Optimum category picking goes one step further by considering variation and cost.

In today’s language, cotton bale selection is a classic problem of raw material optimization. It uses fibre science, yarn engineering, probability, statistical variation, cost modelling, and process knowledge.

The real objective is not merely to buy cotton cheaply. The real objective is to produce consistent yarn at the lowest total cost. That is the art and science of cotton mix profiling and bale picking.

17. General Disclaimer

This article is intended for educational and explanatory purposes. The numerical example used here is hypothetical and simplified to explain the logic of cotton mix profiling, population profile analysis, and bale picking schemes. In actual spinning mills, cotton selection should be based on reliable fibre testing data, mill-specific process conditions, yarn quality requirements, machinery constraints, commercial considerations, and expert technical judgment.

FAQ in cotton spinning-4

FAQs in Cotton Spinning
Q. Discuss about the feed rolls used in opening machine with given headings.
(i) Definition, (ii) Construction, (iii) Fundamental, and, (iv) Types of feeding
Q. Define the beater in opening machine.
Q. What are the objects of beater?
Q. Express the drafts and their calculation. What is the difference between the actual draft and mechanical draft?
Q. What are the objects of carding? How are these objects fulfilled
Q. What is meant by card clothing? With a neat sketch show the parts of a card clothing.
Q. What is meant by neps in carding?
Q. Mention and briefly explain the factors in judging the quality of carding.
Q. What are the effects of doubling
Q. Explain about the function of drawing rolls used in drawing frame.
Q. What is meant by cotton combing?
Q. What are the objects of combing? Explain briefly how these objects are fulfilled.
Q. List the various yarn characteristics improved by combing.

Please see the answers to these questions here

FAQ in cotton Spinning-3

FAQ in cotton spinning-3

Q: What are condensers, what is their role ?
Answer: These are perforated cage rollers. They supply a current of air at a high velocity, convey the cotton uniformly from stage to stage and incidently, perform a bit of cleaning by carrying away the floating dust, impurities and short fibres to a separate collection centre.

Q. What is difference between the conventional and the modern blow room lines.
Answer: Modern blowroom lines have more opening points and fewer beating points.

Q. What is the object of carding.
Answer: The objects of carding are three:
1. To open out thoroughly the tiny lumps so that every fibre becomes individualised and the cotton is no more in an entangled state.
2. To remove all impurities, neps, short fibres etc. which have escaped the blowroom action.
3. To prepare the well cleaned material into a compact sliver form and lay into containers for subsequent processes.

Q. Name the three major regions where cleaning takes place.
Answer: Taker-in and flats.

Q. What are the constituents of flat strips.
Answer: The flat strips are mostly short fibres with some of the impurities like kitty leaf bits etc.

Q. Why speed of licker-in is kept less for longer staples.
Answer: Longer fibres are held for longer time by the bite of the feed roller after the licker-in starts working on them. As a result more teeth act on the fringe of the fibres and there is every chance of fibres getting damaged.

Q. What is back plate. What is its function.
Answer: This ia a curved plate covering the cylinder just above the licker-in and its main function is to keep the fibre bunches delivered by licker-in, remain on the cylinder wire till they are taken by the flats. This also helps to prevent the development of undesirable air currents.

Q. What is front plate. What are its purposes. Why it is called percentage plate.
Answer: This is a plate similar to back plate and is fitted at the front just above the front door. This has a three fold purpose namely:
1. To keep the cylinder surface covered in order to prevent the fibres from flying off.
2. To keep all other material away from cylinder.
3. To provide the opening for stripping and grinding the cylinder.

It is known in America as 'percentage plate' as its adjustment helps to regulate the quantity of flat strips.

FAQs in cotton Spinning-2

FAQs in Cotton Spinning

Question: What are the causes of Cotton Fibre degradation

Light in the presence of moisture has a degrading effect on cotton fibres. Heat also affects strength, stretch and life of cotton.

Q: What are neps. How they are formed

Neps are fine specks in the form of tiny balls of entangled fibres. They are formed due to bad mechanical processing conditions. Longer and immature cottons are more prone to neppiness.

Q: What are naps. Hw they are different from neps


Naps contain fibres whcih are entangled together, but much more loosly than those in neps. A nap can open out while it is not possible to open out a nep.

Q. What is the necessity of a blowroom.

Textile mills are generally located far away from the fields where cotton is grown. Therefore, compressing loose cotton into a compact bale form is unavoidable for economic transportation. This cotton has to be opened in the blowroom.

Also during picking and ginning quite a number of impurities get associated with such cotton, to remove all such impurities from the cotton, blowroom sequence of machines is quite necessary.

Q. Why there are so many machines in the blowroom sequence

The real work of opening, cleaning and blending is done by the blowroom machines. The action of opening and cleaning should be gradual. Therefore, a number of machines are required which gradually open and clean the cotton. The machines in the beginning of the line are mostly expected to reduce the lump size, and the latter machines are expected to open out or still reduce the size of fringes or tufts.

Q. What are lattices in blow room line, what is their purpose

Lattices are made up of wooden legs which are either plain or spiked. Horizontally arranged lattices are mostly plain while spiked ones are meant for lifting purposes. They help to move the cotton ahead in regular and uniform quantities.

Q. What is the purpose of beaters.

The object of beating is to shake out the impurities and force them through specially arranged gridbars and perforated sheets.

Q. Why a three bladed beater is better than a two bladed beater

It is heavier in weight and each blow is more forcible than a two bladed beater. Besides, it gives 50% more beats, which means that this can be run at a lower speed than a two bladed beater and incidently reduces vibrations, wear and tear in the machine.

Introduction to textile sizing

Necessity of Warp Sizing
During the weaving process, the yarns are subjected to three basic physical stresses. These are stretch, strain and abrasion. Although these forces exist in varyiing proportions depending upon the type of loom and the fabric styling,all three are forces that must be considered in all cases.Therefore, the ideal sizing material would produce a smooth, tough, elastic film which would adhere to the yarn. It should smooth to friction and abrasion. It should be tough to endure the load or strain and it should be elastic to allow flexibility and sufficient stretch.

Advantage of using Polyvinyl Alcohol in Warp Sizing

PVA is an excellent film provider. Its tough film is easily removed (desized) with hot water. It leads to the following benefits:

-Superior Abrasion resistance
- Adhesion to synthetic fibres
-flexibility/ elongation
-strength
- user friendly slashing performance.

Yarn sized with PVA can run at lower add-on because of the adhesion and strength advantage PVA provides over natural binders. It requires in quantity only 1/3 rd of the starch.

The excellent abrasion resistance means less shedding on the slasher and in the weave room.

The inherent flexibility of films of PVA resins eliminates the need for high Relative humidity in the weave room. A RH of 65-75% are recommended

PVA solutions are thermally stable and can be maintained for lower periods of time at high temperature.

PVA are widely reclaimed and reused for sizing, thus reducing effluent levels from the finishing plant.

PVA and wax together will provide the optimal size performance. Wax is needed to reduce dryer can sticking, weaker film for easier split, minimize clinging on looms and improved lubrication for the size coating. However, excessive use of waxes can lead to poor adhesion, brittleness, roughness and decreased abrasion resistance. Also waxes can be difficult to remove at desizing stage which can lead to quality problems in desized fabrics. It is important to select a wax that contains an effective emulsifier. It will act to prevent wax from redepositing back on the fabric during desizing. Common wax is tallow.

Starch is primarily used as an extender for PVA to reduce formulation cost. However antistats are needed with starch containing formulations to minimize static on warp yarns. Generally they are not needed with 100% PVA sizes. Antistats funciton as humectants, helping to retain moisture in the film while simulatneously plasticising the film. It includes urea, ethylene glycol and glycerol. Recommended level is 3-7%.

Defomers: Size solution can exhibit foam. For this we need defoamers in the levels of 0.25 to 1.00% based on the weight.

Binders- They are used for synthetic fibres- two major types are polyester or polyacrylic solution.

To avoid lappets warp density: For ring Spun 100% cotton - Spacing between adjecent ends should not be less than the diameter of the yarn. For Ring spun P/C blend spacing should not be less than 1.5 times the yarn diameter. For open end yarns, number of yarns per inch should be 10% less than the ring spun yarns of comparable count.

Viscosity: A properly sized warp will have completely encapsulating (360o) the yarn surface to hold down loose fibres. Internal penetration must be sufficient (15-25%) to anchor the size film to the surface of the yarn. Too low a size viscosity allows liquid to penetrate too deeply into the yarn. Too high a viscosity will not allow sufficient penetration to anchor the size. If ends are tightly packed in the size box, viscosity should be lowered to improve penetration.

Temperature of the size box is important for the right viscosity. High temperature may cause PVA to form skin- causing hard size formation when the slasher is stopped. Recommended temperature is 160-185 o F.

Drying can temperature should be set at the minimum to dry the yarn to hte desired moisture content of 5-8%.

Yarn stretch in cotton should be 1-6%, PC should be 1-1.5%, and Rayon/ Acrylic should be 3-5%.

Desizing agents: Can be water for PVA, NaoH for oils/waxes, HCL for starch, Enzyme for starch, Solvents for oils/waxes or peroxide for PVA.

For more details about textile sizing please click here.

Dyeing of silk with lac dye

Dyeing of Silk with Lac Dye

To extract dye, stick lac is crushed into pieces but not into powder form because at the time of boiling, the sticky resin substance melts and sticks to silk fiber thus damaging the material. These small pieces of stick lac are wetted with water overnight and then churned by which dyes with water come out easily in the form of solution as the dyes are water soluble. It is filtered well and care should be taken that even a small piece of resin is not present in the solution. Depending upon conditions, dyes are extracted from 50% to 98%.

Silk is treated with 2-5% solution( on the weight of the material) of mordant (generally alum) at the boiling temperature for 45-60 minutes. Some times the dyer add turmeric powder (curcuma longa) to get the orange tone. Silk is squeezed only, not washed by fresh water, at this stage. If potash alum is used as mordant then purple color is produced. If copper oxide with ammonia is used then bluish violet is obtained. To get dark red, lead acetate is used, to get reddish yellow, pot. dichromate is used. Copper sulphate produces violet. Barium Hydroxide gives dark red, Tinchloride with Oxalic acid gives pink. Ferrous Sulphate gives a color ranging from grey to black. K2SO4 with Cream of tartar gives violet color.

Dye bath is prepared with the extracted dye solution and rest with water with material to liquor ratio of 1:30. Dyeing is carried out for one hour at boiling temperature. A little solution of myrobalan (Terminalia Chebula retz) is added during the process to achieve greater fastness.

Acidic pH is maintained throughout the process of dyeing and if required the pH is maintained by use of acetic acid. Now dyed material is taken out from the dye bath and washed with fresh water.

About 4-5 kg of stick lack is required for dyeing 1 kg of silk.