Sunday, September 13, 2009

post spinning operations

Post Spinning Operations (PSO)
TITLE: Notes for spinning

Comparison of Winding Packages:
Following is the comparison of three types of winding operations.
Sr. #
SPOOL
CHEESE
CONE
1.
Package having flanges on both sides e.g. warp beam
No shoulders.
Tapered package
2.
Parallel side package.
Parallel side package.
Parallel side package.
3.
Side end withdrawal
over end withdrawal
over end withdrawal
4.
Package rotate during withdrawal
Package remain stationary during withdrawal
Package remain stationary during withdrawal
5.

Center tube is cylinder
Center tube is cone
6.

More withdrawal friction
less withdrawal friction due to angle
7.
Stable package
Unstable package
stable package
8.
Less edge damages
Edges more prone to damage
Less edge damages
Angle of winding
“The angle between the directions of the yarn lay on the package surface and any plane perpendicular to the package axis.”


The greater the angle of wind the better will be the package. Stability will be the greater with greater wind angle.
In drum winding surface speed of yarn remains constant therefore drum speed remains constant.
What is wind?
“The wind is the number of coils of yarn wound on per single traverse from one end of the package to the other end.”
Traverse ratio:
It is the number of coils wound on per complete traverse cycle; therefore it is twice the wind.
Traverse ratio=2×wind
Traverse displacement:
It is done to avoid the formation of hard package ends. By displacing the overall traverse laterally by 3-5 mm uniform package density can be arranged at the package ends.
Precision winding
Comparison of Winding Packages
« Winding rate increase with diameter
« Now in new machines, constant driving speed is possible.
« From start of the package and up to a certain limit spindle speed is constant. After that surface speed is kept constant.
Types of precision winding:
a) Reciprocating yarn guide
Ø In this method a yarn guide is move backward and forward alternately. The speed of precision winder is limited by the reciprocating speed of the traversing yarn guide.
Ø The drawback of this system was jerks and vibration during winding. Due to this reason poor winding took place.
b) Grooved traverse rollers:
Ø In this method grooved drum was used.
Ø Jerks and vibrations are controlled due to grooved drum.
Ø For different shapes and designs grooved drum has to be changed.
Ø No ribbon winding (patterning) problems which was fault of drum winding.
Ø Speed limitations are overcome by using grooved traverse roller instead of yarn guide.
c) Drum winding:
Ø In this method cylindrical drum is running at a constant surface speed.
Ø Invertors control motor is used.
Ø The package surface is in contact with the drum surface.
Ø Package rotates at a speed equal to the surface speed of drum. Hence yarn winding rate can be kept constant.
Ø At constant drum speed rotary speed of package will decrease with increase in diameter.
Ø PATTERNING: “layers of yarn one upon other makes an effect called patterning”. To avoid this, package turn should be in whole numbers. In old method we lift the package for an instance over the drum. Now a days ribbon breakers are used. Also some new arrangements are made on invertors control motors.
Yarn Splicing
Splice:
“A splice is an advance form of knotting the broken thread in which broken ends are combined to form yarn without applying a knot.”
Splicing procedure:
i. Untwist the both loose ends
ii. Overlap both ends over each other
iii. Re-twist them together.
Important points:
« Splice area is 20% weaker than yarn.
« In cotton splice strength is 85% while 75% in polyester.
« Objective of splicing is to produce knot-less yarn.
« Splicers are more reliable.
« Fewer yarn breakages.
« Less maintenance is required.
« Different nozzles may be needed for different type of yarns.
« Air pressure and splice length is adjustable.
Yarn waxing
Waxing is added to machine knitting yarns in order to provide a low uniform yarn tension. Usually paraffin wax with suitable melting point.
To apply wax on yarn we use wax disc and a round plate. Wax disc is adjustable. Hardness of wax disc is very important. Usually 1% wax is applied to the yarn by weight.
We do waxing to,
« Avoid dust and escape of fibers
« Reduce maintenance,
« Fewer yarn breaks during knitting.
« More uniform and reproducible fabric
« Less fly waste at knitting process
« Reduce maintenance,
Yarn reeling
“Reel is a soft package of yarn wound on a rotating swift from which it may be removed in the form of a hank after having the ends tied together”. Yarn may be reeled into hanks for scouring, mercerizing, dyeing and bleaching.
There are two types of reeling,
1) LEE REELING
The hanks are buildup in parallel wound sections. A leasing band is inserted to facilitate unwinding.
2) CROSS REELING
This consists of repeatedly traversing the yarn across the full width of the hank so that adjacent yarn coils cross each other at an angle. This minimizes yarn entanglement during processing.
Modern reels are available in two versions,
a) CHANGE REELING MACHINES
Essentially these consist of two swifts 4 meter long supported in a single pivoted frame. Each swift may be brought alternately into the running and then doffing positions.
b) DOUBLE REELING MACHINES
This type of machine has two swifts each 2 meter long supported in cantilever fashion from center. It is preferred when reeling time is less than 5 minutes.
Yarn polishing
It is used after singeing process. Yarn is passed through brushing surface or brush.
The objective of polishing is to lay-in the surface fibres
Ø To promote yarn smoothness and
Ø Reduce friction in sewing process.
Yarn singeing
This process consists of passing the yarn through a heater at speed varying from 200-800 m/min. singeing is used to remove surface fibres from the yarn surface.
Yarn mercerizing
“it is the process used to increase the yarn strength and luster”.
PROCESS:
§ Immerse the yarn in NaOH solution and a wetting agent.
§ Then follow the rinsing, neutralizing and drying processes.
ADVANTAGES:
§ Luster is improved
§ Dye ability is improved
§ Softness is improved
§ strength is improved (in fabric form 15% increase in strength, 40% if twist less yarn is used)
Factor Affecting Mercerizing:
§ Alkali concentration
§ Temperature
§ Time of treatment
§ Yarn tension ( without tension 30% shrinkage)
§ Yarn twist
PROGRADE PROCESS:
§ “If liquid ammonia is used instead of NaOH in mercerizing, the process is called prograde”.
§ It consists of winding process at about 200m/min in which yarn is immersed in liquid ammonia followed by stretching the yarn in hot water. Then dried before package formation
Advantages of prograde process include,
ü50-100% increase in tenacity/strength then mercerizing
ü33% reduction in elongation at break
üLoop/knot strength increased
üIncrease luster
üIncrease dye affinity
Yarn clearer
There are following three types of yarn clearers,
§ Photoelectric yarn clearer
§ Capacitor type
§ Dual/combined clearer
Yarn clearer has two portions,
i. Detecting unit
ii. Clearing unit
A. PHOTOELECTRIC YARN CLEARER
In this type yarn is passed between a light source and a photoelectric cell. Amount of light received by the photocell determined the yarn thickness.
Advantages:
« change in color can be detected
« change in cross-section can be detected
« moisture will not affect the result
Drawbacks:
« excess of moisture can damage camera (photocell)
« Purity of material can not be detected
« Change in depth can not be detected
« Change in dimension can not be detected
« More maintenance and clearing is required
« less sensitive
Measurements:
Only thick (long & short) and thin (long &short) places were detected.
B. CAPACITOR TYPE
In this method a two parallel plate capacitor is used in which air and material of yarn is used as dielectric medium.
The variation in capacitance is proportional to the mass of the short length of moving yarn between the plates of the capacitor.
Advantages:
« Purity of material can be detected
« more sensitive
Drawbacks:
« change in color can not be detected
« Moisture in and outside the material will change the dielectric value hence result will fake.
Measurements:
Thick (long & short) thin (long &short) places and neps are detected.

C. DUAL/COMBINED CLEARER
It can check,
« Neps
« Small and long thick
« Splice
« Long thin
« F.D & F.L
« Vegetable impurities
« Polypropylene impurities.
(MID TERM EXAM)










Yarn Folding
“Yarn folding consists of combining two or more single yarns together by twisting them around each other in one operation”
« COUNT OF PLIED YARN is
« The EFFECT OF TWIST during yarn folding is that yarn shrinks due to twist.
« “If more than two yarns are folded together then they are called as MULTI-FOLDED yarns”.
« CABLED YARNS are produced by combining together a folded yarn with one or more other yarns by twisting them around each other .Folding of filament yarns is done for tyre cords.
« Variation in yarn strength is reduced. It is possible that CV% of folded yarn may be 55-65% less than the single yarn.
OBJECTIVES OF YARN FOLDING:
ð Irregularity is reduced
ð Luster can be improved
ð Elongation at break can be controlled.
ð Mean yarn strength is increased.
ð Variation in yarn strength is reduced
ð Balanced folded yarn can be produced.
ð Novelty (fancy) yarn can be produced.
ð More compact and bulkier yarns can be produced.
ð F/S ratio of strength increase = 1.1(coarser) to 1.7 (finer)
TYPES OF FOLDED YARNS
There are two basic types of folded yarns,
1. S on Z yarns:
“The folding twist direction will be opposite to spinning twist direction”.
Results of S on Z twist:
ð Yarn extension
ð Yarn becomes soft
ð Resultant twist decreases.
ð Twist in plied yarn will be less than the single yarn.
ð Less than single twist, less than doubling twist given.
ð F/S<1 (F/S ratio =Folding twist /Spinning twist)
2. Z on Z (S on S) yarns:
“The folding twist direction will be in the same direction as spinning twist direction”
Results of Z on Z twist:
ð Yarn will contract
ð Yarn becomes hard
ð Resultant twist increases.
ð Twist in plied yarn will be more than the single yarn.
ð F/S>1
Uses of doubled yarns:
i. WARP: (hard and more strength yarn). F/S > 0.66
ii. WEFT: (soft and less strength). F/S= 0.5 to 0.6
iii. KNITTING: (softer and lesser strength) F/S = 0.5
Balanced yarn: F/S =2/3 = 0.66

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