Tuesday, 30 December 2008
Fibers and DP ( Degrees of Polymerisation)
Nylon 6 -120
Polyester (PET)- 100
Polyacrylonitrile > 2000
Viscose Rayon- 150-350
Thursday, 18 December 2008
On Beam Warpers
1. Lapped Ends
The yarn's broken end is not tied to its end on the warp beam and overlaps the adjacent yarn. The bem is not properly braked, the signal hook fails to operate.
2. Bulges and yarn ends drawn from the midddle
The broken end has not been correctly found and pieced up to the adjacent yarn.
3. Broken ends on the beam
It is due to reasons mentioned in point 2. A group of ends is broken and tied as a bunch or worked-in with overlapping
4. Incision of yarn at the butts of the warp beam or slackness of extreme yarns
The reed is improperly set with respect to the warp beam flanges; deformation of the warp beam flange
5. The number of yarn ends of the beam is excessive or insufficient
Incorrect number of bobbins in warping
6. Conical winding on the beam
Incorrect load applied by the pressure roller
7. Slacks and irregular yarn tension
Improper threading of the yarn into the tension devices; ejection of yarn from under the disc of the yarn tensioning device, yarn tension devices of poor quality
8.Frequent yarn breakages at the beam edges
Burrs and nicks on the surface of the warp beam flanges
9. Improper length of warping
Malfunction of the counter, and the brakes of the measuring device and warp beams
10. Coarse Knots
11. Loose yarn winding
The pressure roller is lightly pressed against the warp roller
12. Working -in of fluff, oily ends and yarn of different density
Careless work of the operative, creeler and oiler.
13. Bulgy winding on the warp beam
Irregular laying of yarn ends in the reed, missing a dent and placing two ends in the adjacent one.
Wednesday, 17 December 2008
Silk Weighted= >1.60
Silk - B. Mori (raw)= 1.33
Length wise shrinkage--> after 3rd wash---> -1.2% to -2.8%
Width wise shrinkage --> after 3rd wash--> -2.5% to -3.5%
Hard Waste % in Denim Industry
Unsized Yarn--> 0.4%
Sized Yarn--> 0.6%
All these above are percentage of Hacoba Production
Knotting + Reknotting waste --. 0.7%
Extra ends--> 0.7%
All the above are as percentage of loom shed production
Total Hard Waste= 4.8%
Tuesday, 16 December 2008
Impact of Rotor machine variables on Yarn Quality
On increasing rotor speed
1. Centrifugal force (g.tex) increases
= (w^2 x 0.981)/20000, w= pi x D x N
where D= Rotor dia in meters
N= rotor rev/second
so there is better fiber consolidation and better strength
2. Combing roll efficiency will reduce , fibres get deposited in rotor groove in bunches and not in single file and so strength reduces.
3. Hooks will get less time to straighten
4. Number of wrapper fibers will increase
5. Also yarn elongation decreases at higher rotor speed
On increasing rotor diameter
a. % wrapper fibres = l x 100/ pi x D
where l= effective length of fibres used
so as D increases, % reduces so strength increases
b. No of doublings inside the rotor
pi x D x TPI
so evenness and imperfection reduces, strength increases
c. Reduction in spinning in coeficient at higher rotor diameter. This leads to weaker yarn.
d. Higher power consumption
PC ( Watts) = K n^2.5 D^3.8
n--> rotor speed ( rev/min)
D--> rotor dia in mm
k--> a constant
e. Yarn elongation decreases at higher rotor diameter
On Increasing Draft
Increasing draft will increase fibers breakage due to increase in the value of carrying factor (ie. no of points per fibre) optimum should be 120-150
Combing roll speed should be around 6000-8000 rpm
Design of Doffer tube
Grooved tube permits yarn to be produced at lower twist factor but poor fiber orientation and high short term variability.
Affeect on Twist
Higher twist: Elongation increase, and abrasion decreases
Sunday, 14 December 2008
Quality Characteristics of OE yarn as compared to ring yarn
Production- Increased 3-3.5 times
Package size- Increased 20 times
Tex Range- 20-60
Twist- 10-15% higher
Average Strength- 15-20% weaker
Variation in Strength- Less
Extensibility- 10% higher
Work of Rupture- same
regularity- 10-20% better
count variation- better
appearance- more uniform
bulkiness- sp. volume increased by 10%
hairiness- 20-40% less
nappiness- fewer neps
yarn faults- decreased by 80%
resistance to abrasion- 20-30% better
fiber blending- much better
take up of size- better ( less size required)
take up of dyes- better ( vivid colors)
End breaks in spinning- reduced 75%
Fly liberation- less
Characteristcs of OE yarn in use and of fabric made from them- comparison with ring spinning
Yarn made from OE spinning
End breaks- reduced by 50%
Knots (after winding)- decreased by 15-17/kg
warp breaks in weaving- decreased by 70%
weft breaks in weaving- decreased by 25%
tensile strength- reduced
tearing strength- reduced
bursting strength- reduced
appearance - more uniform
barring- much much better
cover- 10% better
neppiness- fewer neps
resistance to abrasion- 5-7% better
thermal insulation- 10-15% better
air permeability- 15-25% better
Take up of dyes- better ( vivid colors, clear definitions)
Absorption of water- much better
raising- easier and more uniform
Friday, 12 December 2008
Thursday, 11 December 2008
Tuesday, 9 December 2008
Friday, 7 November 2008
A float or Jala is formed when there is no proper interlacement of the warp and weft yarns over a certain area. The remedial measures are the use of overall high warp tension and keeping the lease rods close to the heald shafts.
Weft Crack (Jerki)
A srip in the fabric where the pick density is lower than normal is calld a weft crack or jerki
Crammed Pick (Patti)
A strip in the fabric where the pick density is more than normal is called a patti. The defect is caused by improper setting of the anti crack motion.
The defect is caused when many ends break consequent to a shuttle trap. The important causes of shuttle trap are : wrong timing of shedding, soft picking, insufficient checking of shuttle in the boxes, severe slough off, and damaged or broken picking accessories.
A weft slough of one or two coils. the main causes of slough are softly wound pirn, overfilled pirns, high density of coils, short chase length etc.
Improper Weft Threading (Single Moti)
The defect is characterised by a loose and uneven selvedge consisting of weft and warp protroduing loosly beyong the true selvedge line.
Hardened fluff, as well as foreign matter such as piece of leather accessories or wood chips, woven into the texture of the fabric is called a gout.
In this defect, the yarns are distorted from their true paths and fine holes are caused near the selvedges. Unsuitable choice of temples and poor mechanical condition of temples are the main causes of this defect.
The defect is characterised by uneven and distorted appearance of the fabric, because of hard gummed spots in the warp. Use of cold size or keeping the immesion roller dipped in size during a long machine stop causes such spots.
Stains are caused by lubricants and rust. Most of the stains can be traced back to poor manintenance and material handling.
Thursday, 6 November 2008
Common Fabric Defects
1. Weft Streaks
These are faint or sometimes prominant lines along the lenght of the fabric. Use of good quality reeds will largly reduce streaks due to uneven end spacing. Streaks can also be avoided through careful housekeeping and ensuring that different batches of yarns do not get mixed up.
This defect is characterised by a general grouping of warp ends drawn through individual dents of the reed with a fine crack showing up in between such groups. This is caused by
- insufficient tension difference between the shed lnes during beat up.
- excessive warp tension
- late shedding
3. Irregular reppiness
It is characterised by the prominance of alternate picks over small areas on one face of the fabric. The following precautions can help to minimise the occurrence of reppiness.
a. Worn out tappets and tradle bowls should be replaced
b The back rest should be raised by about 4 cm with respect to the fell line.
c. The emery rolles should be in good condition.
d. An increase in warp tension within workable limits helps to reduce this defects.
4. Small weft loops ( phurkies)
A phurki is a weft loom protruding from the cloth surface. Generally, the length of the yarn in the loop is not sufficient to permit snarling. These loops may protrude from both faces of the fabric. Early shedding, incresing warp tension within workable limits, use of good temples and adequate size pick of about 12% or higher - these measures can be used to prevent the occurrence of phurkies.
5. Curled and folded selvedges
This defect is characterised by the appearance of curls and folds in the fabric selvedges. The following points merit attention:
a. Denting order- the number of ends per reed dent in the selvedge should be 50 to 100% more than that in the body.
b. Warp Tension- An increase in warp tension results in a tighter selvedge.
c. Selvedge construction- The selvedge yarns should be preferably two ply and should be drawn one end per heald eye.
6.Missing Interlacement of weft at selvedges
In this defect, a group of extreme warp ends in the selvedges do not interlace with the weft over a fabric length of 1 to 4 cm. The main cause of this defect is excessive tension in the weft yarn.
7. Weft snarls
A weft snarl in a fabric is caused by a short length of three fold weft yarn of which two folds are intertwisted.
The incidence of such snarls can be reduced by ensuring the process setting of twist and by minimising the possibility of severe rubbing of yarn between the shuttle and the box front plate.
8. Weft Bar
A weft bar is dark or light band across the width of the fabric which shows up prominantly particularly in dyed fabrics.
Medium to long term periodic irregularity in yarn will produce regular weft bars in the fabric.
The remedial measures can be:
a. Better process control such as:
i. uniformity of count on groups of ring frames spinning the same count.
ii. Prevention of periodic irregularity in the yarn.
iii. Control of winding and pirning tension.
iv. Proper maintenance of let off and take up motion
v. Control over blend proportion.
vi. Better housekeeping to prevent mixing up of yarn from frames.
9. Broken Picks
In plain woven fabrics, this defect materialises by the presence of two picks in the same shed for a part of the width of the fabric.
The main cause of weft breaks are rough surfaces of shuttle, shuttle box, rough or incorrect placement of shuttle eye, loose fitting of pirn in the shuttle, incorrect alignment of pirn with shuttle eye and low yarn strength.
Lashing in is the term used to describe bits of extra weft yarn found tucked into the selvedge of the fabric.
Remedial measures are:
a. Proper maintenance of accessories and loom parts.
b. Adjusting the pattern of changes of the boxes.
c. The use on drop-box looms of a suitable brush fixed at the end of the temple rod.
11. Missing End (Chira)
A defect where one or more warp ends are missing in the fabric is called a chira. This is the most frequently occurring defect in Indian fabrics and constitutes 40-50% of the total defects. Most chiras are caused by broken that are not mended immediately.
It can be prevented by minimising missing ends in the beam and efficient maninteance of the warp stop motion.
Effective supervision to ensure that a broken end is not left unmended for long can also minimise the occurrence of chira.
Wednesday, 5 November 2008
Maximising Loom Efficiency at Loom Shed
Control of Stops:
The various stops can be classified as
1. Stops due to warp breaks and weft faults
2. Stops due to weft breaks
3. Stops due to shuttle changes
4. Stops due to mechanical failures
1. Stops due to warp breaks and warp faults
Given a quality of yarn, the end breaks during weaving are increased by
- Preparatory deficiencies such as uncleared yarn faults, unsized beams, excessively starched yarns etc.
- faulty loom settings
- defective loom parts and accessories
-unsatisfactory atmospheric conditions
The stops due to warp faults such as slack ends, sticky ends, cross ends, missing ends etc. are due to preparatory deficiencies.
2. Stops due to weft Breaks
Given the quality of yarn, breaks are mainly influenced by unwinding tension and package faults.
The unwinding tension in turn depends upon
- The condition of the surface of the pirn
- shape and dimension of the pirn
- condition of the shuttle accessories, such as shuttle tongue, shuttle jaw
3. Stops due to shuttle changes
4. Stops due to Mechanical Failures
The more common mechanical failures are: faulty working of the warp-stop-motion, weft-stop-motion, pirn transfer mechanical, fast read motion, bang off and shuttle trap.
5. Miscellaneous Stops
All other stops no caused by the earlier four categories such as stops due to beam gaiting, repairs, oiling and cleaning, and delays due to shortage of pirns, beam accessories are included here.
6. Quality of Yarn
It is proven that in mills where there is a consistently low warp breakage rate, the yarn CSP is higher and also the number of thin places is less than the certain minimum level.
7. Loom Performance
In order to determine whether the prevailing breakage rate is really different from the norm and to compare the effect of two treatments say two different size mixings, the appropriate tests are:
((O-N)^2)>=4 and ((A-B)^2)/(A+b) >=4
where O are observed breaks and N are norms for breaks. A and B are breaks with different treatments
Control of Loss of efficiency by Snap Reading
Snap reading is a technique that helps both in listing the various causes of loss in efficiency and in estimating the percentage loss due to each cause. For taking such reading, one walks down the loom alleys making the tally of looms that are stopped against a list of the causes of stoppage.
For example, in a shed of 800 looms, after taking 25 rounds of snap readings, if 4000 looms are found stopped, then the loss of loom efficiency is (4000x100)/(800x25) = 20%
If out of the stopped looms, 1600 looms are found stopeed due to end breaks and warp faults, the loss in efficiency due to this cause is 8%.
OPTIMUM LOOM ALLOCATION
Generally when we answer this question "How many looms per weaver", we should taken into account both operative and machine efficiencies simultaneously.
Thursday, 23 October 2008
Warp Preparation for Rope Dyeing-II
Oz tensioner: It consists of round cylinderical housing and is located at each running package in the creel. At the top and bottom of the housing is a small ceramic eyelet. Inside of the housing are two steel balls.The yarn is threaded up through the bottom eyelet, around the steel balls out through the top of the housing.
Tension is applied to the yarn as it passes around the steel balls inside of the housing.
Advantages: Tension at the front and back of the creel is constant. 2. Adjustments are never required. 3. It is almost maintenance free.
1. there is a limit to how much tension can be applied
2. Threading of tensioner is difficult
3. It is relatively expensive.
1. Capastan Type
2. Rotating Disc Type
Capastan Type: There is a round capastan mounted on a precision shaft. This capastan is positioned onto the bearings which are located inside of a round DC coil. The yarn is wrapped around the outer surface of the capastan. The action of the yarn being pulled out of the creel by warper rotates capastan. If no voltage is applied to the DC coil, an EM field is created under the capastan. A hysterisis ring is attached to the inside of the capastan which reacts to this EM field and as such creates resistance to free rotation of the capastan. This resistance to rotation adds tension to the yarn on the capastan's outer surface. Varrying levels of DC voltages are applied to each tensioner in the creel and will provide equal tension to each in the rope.
Rotating Disc Type: Two disks are mounted in the vertical position onto a ceramic shaft. Behind the inside disk is a DC coil. When voltage is applied to the DC coil, an electromagnetic field is created. The outside disk is steel and is of course attached to the magnetic field which has been created. It pulls tightly against inner disk; again depending upon the strength of the EM field created by the DC coil, the yarn is threaded between the two disks. A 4 RPM AC motor mounted on each tensioiner, turn these disks to prevent thread cutting.
Advantage of Capstan types:
- No electric motor
- yarn is not distorted due to pinching action of disk
- less maintenance
As speed of ball warping is slow, mechanical tensioner are normally sufficient.
5. After that the yarn is then threaded through the eyebrows down the length of the creel. Here self threading type of ceramic eyelet is generally sufficient.
6. A stop motion device is required
a. The drop wire system
- It is located on each vertical row at the front of the creel bands.It is inexpensive with very short reaction and response time.However, it is exposed to dust, and if the end should break at or near the warper, there may be enough residual tension on the yarn, holding it up and preventing the drop wire from falling.
b. Photoelectric system
Instead of drop wire, this system uses a faller which is attached to a shutter inside of an airtight housing. Inside this housing is a photocell having a transmitter at one end of the housing and a receiver at the other end. A light beam is emitted to the receiver and an open electric circuit is maintained. When an end breaks, the faller drops and the attached shutter passes through the light beam, thus imitating the stop signer to the warper. it is reliable, comparatively inexpensive, easy to thread and maintenance free. However,it suffers from the same problem of residual tension.
c. Electric Motion Sensor
It is normally mounted on the balloon shield at the yarn package. This system actually measures the motion of the yarn as it exits the package. The yan balloons through a light beam housed in the balloon shield. As long as the light beam is constantly broken by the ballooning motion, the system remains open when the end breaks, the ballooning action stops and sensor signals the warper to stop. The circular motion of the yarn passing through the light sensor keeps the lenses clean. It is reliable, fast acting and self cleaning. However it is expensive.
7. The yarn exists the creel and is threaded through the lease stand. It houses a unique reed which allows each adjacent yarn end to be raised or lowered in order to create a shed through the yarn sheet. A lease string is inserted through this shed at given intervals ( 1000 m) in order to maintain control of the yarn during reopening at the long chain beamer. It can be manually or pneumetically operated.
Wednesday, 22 October 2008
Tuesday, 21 October 2008
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.
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.
Monday, 20 October 2008
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.
3. Factors effecting Loom efficiency
Various factors that affect the loom shed efficency are
2. Human ( Related to weaver skill and work methods)
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
Sunday, 19 October 2008
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
Reeds are generally counted using STOCKPORT system, which is based on the number of ends in two inches.
Ex. A 72s stockport reed means 72 dents on 2 inches or 36 dents per inch.
Particulars of reed while ordering
100s ST, 18 G., 44"x 5" blue
- Stockport reed of
- 100 count
- using dents of 18s wire gauge
- Reed is 44" long
- 5" deep
- there will be blue paper on baulk of the reed.
Ex. What will be the number of ends/inch in a reed of 3/80s stockport
80s stockport= 80 dents per 2 inches
= 40 dents per inch
Therefore no of ends per inch = 3 x 40 = 120
When a set contains 4 shafts, it is called a plain set.
The number of heald eyes per inch across the healds in a set expresses the count of the heald.
Ex: 60s count for a plain set means 60 heald eyes on 4 shafts per inch i.e. 15 eyes per inch per shaft. For a 6 shaft set, it becomes 60 heald eyes on 6 shafts per inch i.e. 10 eyes per inch per shaft.
Ex. Find the count of healds that will be required for weaving a 6 shaft satin fabric using 72s stockport reed, drawn 3 ends per dent.
No. of ends per inch in the reed = (3x72)/2 = 108 ends
Therefore no of healds /inch = 108/6= 18 healds per inch.
Thus we require 72s count of reeds in a plain set.
Saturday, 18 October 2008
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.
Friday, 17 October 2008
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 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 !!
Thursday, 16 October 2008
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
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%
Wednesday, 15 October 2008
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
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
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.
Tuesday, 14 October 2008
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.
Monday, 13 October 2008
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
Mutton tallow= 7.5
Preparation of Size Receipe
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.
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
1. Size add on = 18 %
2. Increase in strength % = 5.2
3. Elongation at break % os sized yarn = 6.8%
Saturday, 11 October 2008
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
-quality of beam
-a method to calculate the expected level of productivity
Friday, 10 October 2008
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.
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.
Friday, 3 October 2008
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.
Thursday, 2 October 2008
Process Control in Warping-3
Maintenance Check points at Warping
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
In case of high speed warping machine, check tension weights at every count change- regularly
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.
1. Check for concentricity- half yearly
1. Check for the conditions of flanges and beam shafts, repair damaged beams- regularly
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
Tuesday, 30 September 2008
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
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.
Monday, 29 September 2008
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.
Friday, 26 September 2008
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.
Thursday, 25 September 2008
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.
Tuesday, 23 September 2008
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.
Thursday, 11 September 2008
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.
Saturday, 6 September 2008
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.
Friday, 5 September 2008
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.
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"
Tuesday, 19 August 2008
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.
Diameter of hole in inches= constant x sqrt (grains/yard of sliver)
Question : How does the setting to the following pair of card points affect the quality of sliver produced.
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.
Sunday, 17 August 2008
Process Control in Cotton Mixing
These two lectures answer the following questions:
1. How can I decide about cotton mixing for denim.
2. How can I decide about cotton mixing for making knitted fabric.
3. What is information required for an optimum cotton mixing.
4. What is an ideal cotton mix.
5. What are the steps to create an optimum cotton mix.
6. What are the four components of yarn quality. How each of these is affected by fiber quality.
7. What values of yarn quality parameters can be obtained from a cotton mix of particular fiber attribute.
8. For some pre specified values of yarn characteristics, what are the average values of fibre attributes that we should in cotton mix.
9. What are the various problems due to cotton mixing vairations, case study of fabric barre.
The answers to the above questions will be found here.
Saturday, 16 August 2008
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
Friday, 15 August 2008
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.
Wednesday, 13 August 2008
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.
Tuesday, 12 August 2008
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
- 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
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.
Kullu is a place in Himachal Pradesh. It is famous not only for entertainment and beautiful sceneries but also for its traditional textiles named Kullu Shawls throughout India. Kullu shawls are pure woollen shawls having traditional designs.
Kullu shawls are made from woollen yarns. The fibres for this yarn are collected from sheep and then sorted out (near front legs and neck, best quality of wool is found on a sheep) according to color, length, quality and feel. The fibres are processed by domestic methods. Under these methods, the fibres are sorted, scoured and radical impurities are removed and then these fibres are dyed by tub dyeing method. Then the fibres are spun into yarn by charkha and Takhli. Now-a-days few quantities of silk and cotton are also used for borders, pallau and centre motifs. Somethimes greige fibres are also used to produce produce patterning and motifs.
Though Kullu shawls are produced in different colors like china blue, olive green, maroon coffee etc. but beauty of Kullu Shawls stands only in black shades.
Because Kullu Shawls are not made by big machines, this is an art of hand woven technology. Sometimes Zig-zag effects are also produced.
In Kullu shawls small diamonds, small dots, small squares, small triangles, plus marks etc. are found on the body of the shawls. there may be small lines of patterning on the selvedge or border with matching colors.
Kullu shawls are of woollen yarn of high count and shape just like 10s of cotton yarn. This is optimum to have better quality.
Panipat is famous for carpets. Regarding the origin of carpets there is no proper clue available in history about when carpet manufacturing had started in India, but it is sure that thousands of years agao, the Rishi Munis used an Ashram Cloth material which is a part of carpt of ancient days. In 15th century, carpets were available in well developed homes.
Though carpets are known as woollen carpets but woollen yarn alone is not able to produce perment structure while working without the help of cellulosic fibres, that is why carpets are woven by woollen and cotton yarns. Carpets of 15th century show that in warp wool is used and in weft cotton is used. It is a style of 'dari'. Now-a-days different types of fibres are used in carpets eg woollen, silk or cotton carpets etc.
Carpets are woven with the help of different techniques. Some of which are given below:
1. Loom carpets are woven in 'dari' style, means hundred percent warping of cotton threads and 100% woollen threads as weft yarn with extra weft yarn for loom weaving.
2. Few carpets are woven with the help of latest machinery, some computerised techniques are used for lifting the yarn and loading the yarn to produce carpet effects.
3. Hand tufted carpets are latest carpets now-a-days. Such carpets are woven with the help of tufting gun. To produce such carpets the base fabric is cotton fabric in dense weave. These carpets are produced by tufting guns according to required design.
Generally loop carpets are produced in very dark and medium colors and light colors are mainly used in tufted carpets. Light, medium and dark all types of colors are used but it depends upon taste of country to country eg. carpets of Germany are usually in medium colors and dark colors, Americans never like purple dark colors while Australians use light colors.
In India floral designs are used very much while in Western countries ( European ) geometric designs and mural designs are liked. Commonly in America the designs of latest inventions are produced on the carpets eg. trains, buses, sea coasts, dinosaur etc. Though carpet is a very much expensive style of weaving as well as precious traditional textile of India.
Sunday, 10 August 2008
Kanchipuram is a city near Chennai (Madras) in Tamil Nadu. Kanchipuram produces brocaded silks of superb texture, color and lustre, known as kanchipuram Sari.
The raw material for Kanchipuram sari is silk and Zari. The silk is brought in from Bangalore and Zari threads for brocading come from Surat Gujarat.
The main items of production are the silk saris with the solid brocaded borders ('korvai'). The silk is woven on a throw shuttle pitloom with a drawbox harness. Designs and patterns are woven with extra warp and extra weft and are worked into the body of the fabric by means of an indigenous device known as the 'adai' which fulfils the same function as the jacquard.
Kanchipuram Saris in the south Indian style have a pallav and/or borders, that contrast in color to the main field of the sari.
Green, blue, red, yellow, mashroom, orange or purple colors are commonly used with contrasting borders.
On the borders, small flowers, mangoes and geometrical motifs are woven with zari. Pallu is also highly decorative part of the sari. Nowadays, artificial zari is used commonly.
Saturday, 9 August 2008
The Coromandal coast of India was once a world renowned source of fine hand painted textiles, fortunately its textile tradition is survived in AP temple town of Kalahasti where the paintings of scenes from the Hindu Epics on cotton cloth was revived by the establishment of a training school by the All India Handicrafts Borad in 1958.
On Kalamkari cloth, printers and painters use both natural and chemical dyes. Though indigo is found in abundance in the area, but their red shades came from chemical alizarin.
Kalamkari is practiced in east of India at Masulipatnam in AP and Kalahasti in South. In Masulipatnam, the agents that control the patterning are traditionally applied with a kalam (pen). Machine loomed cloth known as Kora is bleached by repeated immersion in a solution of goat or buffalo dung and frequently rinsing in a river or a canal. The cloth is then mordanted in a myrobalan solution, to which is added fresh buffalo milk to prevent the spreading of the dye or application. Outline printing of the floral, bird and animal patterns is done with black (made of iron salts and gum) or with red ( alum with gum) or with both colours then follows the washing and the cloth is left to dry for two or three days. After washing, the cloth is scalded in a vat of alizarin and madder solution, enhancing and fixing the red patterning and removing the myrobalan and gum juice. Bleaching then takes place, leaving a white cloth patterned in red and black. Cleaning, bleaching and starching follows prior to the painting of the cloth in yellow and green colors. Yellow is achieved by boiling myrobalan flowers in water and by applying the solution with a simple Kalam made from a short pointed bamboo stick whose dye reservoir is a felt pad bound with string. Pressure on the myrobalan soaked pad allows the artist to control the release of the dyeing agent. the dyes are fixed permanently by dipping the cloth in an alum solution, after which it is part bleached in cow dung solution to give the yellow an attractive clarity and color. Finally the cloth is soaped and washed.
Unlike the Masultipatnam cloth the hangings from kalahasti are decorated entirely by free hand use of Kalam pen. Machine loomed cotton cloth is washed to remove starch and soaked in myrobalan solution ready to take the black dye. Once spread on the ground, or on a low wooden bench the cloth is ready to be sketched on by the artist. Oulines of figures and designs are first drawn freehand with charcoal sticks made of tamarind twigs. The kalam for fine linework is a pointed bamboo stick, six to eight inch long swaddled at the sharpened end with welt or wool that is tied to the cane by a net of strings. The felt pad holds the dyestuff, which may be released by slight varirations of finger pressure to run down to the point of kalam and on the cloth as the designs are drawn. Black outlines are painted with the kalam using a solution of salts of iron. An alum solution is painted as infill with a bamboo kalam. The cloth is then immersed into a solution of pobbaku leaf, surudu root bark and majistha root and the mordanted areas are coloured red. Double mordanting of figures and patterns with alum creates tones of red and the cloth is then bleached in a solution of cow's dung. The final colurs of yellow, blue and green are painted on the cloth as infill and detail with a kalam. Yellow is obtained by painting a myrobalan flower solution as areas pre-mordanted with alum, blue by applying indigo mixed with a little alum and green by coating yellow areas with indigo.
In Kalahasti, the subjects of illustration are either traditional takes from Hindu epics, or modern as scenes from company logos. Also there is a religious code for the decoration of Kalamkari fabrics. All gods are blue, female characteristics are golden yellow, bad characters and demons are red.
Friday, 8 August 2008
These are fine transparent cotton muslin with discontinuous supplementary weft motifs woven in heavier cotton threads.
Jamdani weaving methods employs two weavers sitting side by side at a simple handloom who add every discontinuous supplementary weft motif separately by hand , using individual spools of threads called tilis. No special warp lifting mechanisms are required.
In terms of color and design, contemporary Jamdanis fall into six categories: those with
1. Natural coloured, unbleached cotton grounds with bleached white cotton supplementary work.
2. Pastel coloured grounds with white supplementary work.
3. Dark coloured grounds with white supplementary work.
4. Any of the other, with coloured threads, either of similar or contrasting tones.
5. Any of the above combinations with 'zari' supplementary threads as part of the mix.
6. Dark grounds with only zari supplementary work.
The only town in India where traditional Jamdanis are still made is Tanda in Uttar Pradesh. Here finely patterned white Jamdanis usually completely covered with vines and foliate patterns, have been created since at least the nineteenth century. Today most Tanda Jamdanis are woven into dupattas or yardage, although sais of this type were most popular among wealthy old women and widows.
Thursday, 7 August 2008
Alipura is traditionally the district of Varansi, where the famous Benaras brocades are woven, brocades are textiles woven with warp and weft threads of different colors.
The Benaras brocades are woven in silk, with profuse use of metal threads on the 'pallaus' and the field of the sari.
The weavers are muslims, known as karigars. The brocades are woven in workshops known as karkhanas which are a series of interconnected rooms, usually on the first floor. Almost every square inch of ground space in the room is taken up with looms, and above each loom hangs a crowded arrangement of strings leading down to the loom heddles. the weavers work in artificial light, in a calm and quiet atmosphere which is conducive to the concentration needed for the weaving of such complicated designs.
The Zari thread known as kalabathun consists of finely drawn gold, silver or base metal thread, wound round a silk thread. Silk traditionally come from Bengal, Central Asia and Italy, but now comes from either Malda, in Bengal or from Kashmir or Japan.
The most famous brocaded textile of Varansi is called Kinkhab woven with coarse but durable silk called Matka which is heavy enough to take brocading with gold or silk thread. A silk and zari work brocade of lighter material and less heavy ornamentation is known as 'pot-than' or 'bafta'. The name for brocades without any metal work is called Amru.
Wednesday, 6 August 2008
In India's legendary heritage of textiles, few are as highly prized as patola, the double ikat silk fabric, in which both warp and weft are separately tie-dyed before weaving to create patterns of unmatched richness and subtelty.
Patan, the ancient capital of Gujarat has been the centre for patola for many centuries.
In Gujarat they are traditionally worn by Hindus, Jains and Vohra Muslims. A well to do bride invariably wears a patola today. Throughout India, Patolas have become a symbol of wealth and family lineage, transcending the boundaries of Religion and community.
The complicated patola weaving procedure is naturally labourious and tedious and it is possible to complete only about 25 cm of cloth a day.
To begin with, skeins of silk are opened and wound on reels. Once this is done, eidth threads are plied together by lightly twisting them and feeding them into another hand reel. This twisting prepares the silk for the next stage- bleaching.
Bleaching is achieved by soaking the hanks of silk for a minute in boiling water mixed with soda ash and soap. Once dry, the silk is filled into bobbin and wound onto a charkha. It is then twisted and transferred to a smaller charkha. From this warp and weft are prepared.
Befor the tyeing and dyeing can start, the pattern is first traced onto a graph paper.
The warp is assembled with the help of round iron or steel pegs covered in white muslin, protruding horizontally from the wall. The number and arrangement of the pegs can be altered to suit the desired length of the warp. Twelve wooden bobbins on stand, containing the eight ply silk, ar placed in two rows in front of the pegs. The warp is spread on a rectangular wooden frame and sectioned by grouping the threads accorging to the pattern.
Once the wapr and weft are ready on the frames, the tyeing begins, always from the right with the use of thread or old cloth, exact measurements of the portions being tied are taken continuously. Of all the phases of the weaving process, this is the most delicate and often it is done by women. As different portions of the yarns are tied, it is removed from the frames and dyed. This process continues until every color in the pattern appears in the yarn.
The dyeing, traditionally achieved with vegetable colors, but now increasingly with chemical dyes, is carried out by both men and women. Hanks of silk are usually left soaking in cold water for a day or two before each dyeing to ensure that the colors are absorbed evenly. The yarn often needs to be vigourously rubbed by hand for it to be properly soaked. After the final color has been dyed, the yarn is yet once more returned to the frame. Now the entire pattern becomes clearly visible. The weft is separated and taken back onto bobbins for weaving.
The patola loom is very simple and tools are hand made from bamboo. The loom does not have a foot paddle but a handle by which threads are manipulated. It is placed at right angle to the floor and two people are required for weaving. The first stands on the right and passes the shuttle to the left and the second sits in front of the loom and passes the shuttle from left to right. While at the loom, the weavers hold the weft threads on both sides, constantly checking for a missmatch in the pattern between warp and weft. The process is painstakingly slow. Little wonder then that it takes roughly 20 days to finish a sari about five meters long.
There are some 10 basic patterns, mainly of plant, zoomorphic and geometrical motifs. While most motifs can be traced to traditionaly forms, some relatively modern ones certainly evolved in response to the demands of the export market. In a weaving technique so complicated, it is true that geometrical motifs should predominate. These were used in variation between the border and the body pattern. The designs most commonly found include chhabdi bhat (the basket pattern), Fulvari bhat (flowering pattern), ratan chowk bhat ( jewel mosaic), Paan bhat (pipal leaf pattern), akhrot bhat (walnut motif), nari kunjar (women and elephant), popat kunjar ( parrot and elephant), wagh bar hathi bar (tiger and twelve elephants), maharas bhat ( women dancing with sticks in hand)