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Yarn Preparation (Winding)

Process/processes of preparing the yarn produced on the

spinning machine to meet the requirements of su bsequent

processes, such as weaving, knitting and y arn dyeing

Clearing, winding and waxing are usually performed on

one machi ne: WINDER

Objectives of yarn preparation

Clearing: fault removal

Winding: transferring yarn from one package form to another

Yarn treatments: e.g. waxing, steaming and conditioning

Warping: preparing the w arp package (beam)

Sizing: mainly for preparing the warp for w eaving

Yarn must not be damaged during winding

Winding requirements

Yarn fault must be reduced to the required level

Yarn tension must b e appropriate and as

uniform as possible

Package size, shape, build must meet the

requirements of the next process

Package types

Cylindrical

Cheese (with / w ithout flange)

Pineapple cheese

Pirn

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Cone

Package requirements

Size

Density

Stability

Unwinding performance

Package Build

Parallel build

High density

Unwinding is restricted

Flange is often required

Low stability

Parallel Built PackageWith Taper (Roving)

Cross wound (quick traverse)

Lower density

Better stability

Large fluctuation of unwinding tension

Compromise of density and ease of withdraw

(shorter traverse length)

Chase build (progressive conical tr averse)

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Main layer

(slow lifting of ring rail)

Ring Package (Cop)

Tube

Cross layer

(fast descending)

Package building

motion

D

D

Basic theory of winding

Ang le of win d (two defi nit ion s)

Ang le between yarn and package ax is

Ang le between yarn and any plan e perpendi cu lar t o

the package axis

Vt

DpNp

Vt

Vp Tan

Winding speed

NpVp

Vt

Vw

Dp

22VtVpVw

Angl e between yarn and package axi s

Effects of Angle of Wind

Package Density

Minimum Density at 45o

Maximum Density at 90o (Parallel Wound)


Package Density

Package Stability

Maximum 80o

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If winding angle is too l arge,

coil pitch can be too small on tube (small D),increasing risk o f yarn entanglement

Coilpitch


Package Density

Package Stability

Traverse speed

Power consumption

Accelerat ion for ce on yarn gui de

Normal range: 70o~80o

(limit depends on yarn type and wi nding speed)

Vt

VpTan

Number of yarn coils wound o n package during one

single traverse (from one end of package to other end)

Wind

Number of yarn coils wound per complete traverse

cycle (from one end of package to other end and back)

Traverse r atio

It is twice the wind

Nt = Vt / 2Lt

Lt = traverse length

Vt = traverse speed (ignoring reversal effects)

If

Number of double traverses per minute

(traverse rate):

Lt

Traverse ratio Tr = Np/Nt

Traverse Ratio:

Number of Yarn Coils per Cycle (Double Traverse)

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Tr = 10

Tr = 5

Patterning (Ribboning)

Repeated winding of yarn at exactly t he same

place on the package during successi ve

double traverses

Patterning causes

Poor unwinding performance

Uneven colour i n dyeing

Traverse Ratio=3 Traverse Ratio=2.5

The yarn will return to its starting pointafter n double traverses

With a traverse ratio ofw +m/n

w, m and n are integers

m < n

m and n have no common factors

5-1/15 5-1/20 5-1/37 5-1/43 5-1/68 5-1/1000 5+77/10000

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Traverse method

Reciprocating yarn guide

Traverse method

Reciprocating yarn guide

Characteristics

Speed limited by inertia

Flexible in package formation

No appreciable twist displacement

Grooved Drum

Traverse method

Mainly used for spun yarns

Grooved drumCharacteristics

Usually also act as package drive roller

No inertia problems

Lower energy consumption

Less maintenance cost

More twist displacement

More yarn abrasion by drum

Higher tension is required

Traverse method

Rotating blades

Traverse method

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Not widely used

Rotating blades

CharacteristicsNo inertia problem

Flexible package formation

Blades can cause yarn damage

Blades may lose control of yarn atreversal points, causing traverselength variation

Traverse method

Package drive

Friction drum

Not suitable for yarns withlow abrasion resistance

Direct drive

Constant rotational speed

(wide application)

Constant surface speed(expensive)

Traverse ratio decreases

Random winding

Package surface speed (Vp)

and

Traverse speed (Vt orNt)

are constant

Since tan = Vp / VtAng le of wind i s cons tant

But Np = Vp / DpDp inc reases

Np decreases

During winding

Tr = Np / Nt

Tr =Np/Nt =Vp/DpNt

Smaller Dp Faster Tr changes

But package diameter Dp increases

So package surface speed

Vp=DpNp increasesAnd

tan = Vp/Vt increases

Precision Winding

Package rotational speed (Np)

And traverse rate (Nt) are constant

Tr = Np/Nt

Traverse ratio is co nstant

So winding angle increases

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Combination of precision winding and random winding

Some general aspects of pr ecision winding

Package drive (cons tant Np)

Patterning (avoided by su itable traverse ratio)

Limited package diameter (winding angle/speed)

Variable productio n rate

Close-winding and open-winding

Close Wind Open Wind

The magnitude of the gain determines how close to each

other yarn coils from suc cessive double traverses will be

Precision Winding

Gain

If the traverse ratio is w + z

where w is an integer

Yarn coil from succ essive layers

will be displaced by z revolutions

z is the gain

Gain can be positive or negative

Dp

Lt

y

Dp/2 y=zDpy=d/cos

Traverse Ratio=2+z

y

z

d

yd

Z = y/(Dp) = d/(DpCos)

For close winding:

Yarn diameter (count, tw ist, fibre type)

Package diameter

Winding angle

The gain required for close wind ing depends on

Z = d/(DpCos)

The loss of traverse length at highpackage speeds

Limits of winding speed

The inertia of the yarn guide (Nt ~ 450 d.t./min)

The traverse ratio (Tr= Np/Nt)

The angle of wind (70o ~ 80o)

The textile limit imposed by the yarn

(~1200 m/min for spun yarns)

Winder speed can be much higher

Vt

VpTan

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Short term tension variation

Cheese: length of t hread path varies fromthe middle to th e ends of package, causing

speed variation and tension variation

Cone: yarn speed varies along package length


Cheese: length of t hread path varies fromthe middle to th e ends of package, causing


Cone: yarn speed varies along package length

Short term tension compensators


Cheese: length of t hread path varies from

the middle to th e ends of package, causing


Tension Control

Yarn tension must be controlled within limits

for good package formation, correct package

density and minimum yarn damage

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Over-end Unwinding

Unwinding tension

Adds tw ist

Extra tension is usually applied

Less affected by yarn s peed variation

Tension varies as balloon height changes

Friction (low speed: yarn sliding on the surfaces

of tube and p ackage)

Balloon (high speed)

Stationary package

Over-end

Unwinding tension

Side Unwinding

Unwinding tension

Only applicable to high tension w inding (e.g. coarse industrial

yarn) and low s peed negative let-off systems (e.g. warp supply)

Rotating package

Rotational speed must vary to maintainconstant yarn speed

Positive driven

Negative let-off

Inertia changes with package weight

Accelerat ion and deceleration cause lar ge tens ion fluctu ation

Package must be retarded

on package surface

on spindle

Package growing at high s peed

Yarn tension can not be kept low and regular at high speeds

Side Unwinding

Inexpensive

Tensioner

Easy to thread

Easy to adjust

Yarn tension within specified limits

Unaffected by yarn lub ricants, loose fibres and fly

Easy adjustment and self-compensating for wear

Not affecting yarn twist dis tribution

Device to Increase Yarn Tension Durin g Winding

Requirements

T1 T2

Yarn pathdirection

T3

11

12

eTT

eTTinout

22

23

eTT

2211

1

eeT

)(

121 eT

Tensioning devices

a) Friction rods: multiplicative

Magnifies tension fluc tuations

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eTTinout

Example

Tin = 101 g

10

e

Tout = 10010 g

T2T1

P

T2T1

P

T2 = T1+P

T2 = T1+2P

b) Tension roller and plate

c) Two tension plates

(b) and (c) are additive

Influenced by

Can cause twist redistribution

and twist variation

dirt accumulation

localised wear

T2 = T1+PExample

T1 = 101 g

T2 = 1001 g

P = 90 g

Constant Torque

Pulley Rotates with Yarn

No Slippage

Pulley tensioner

pulley with constant torqueyarn pulls it around without slippage

P

Disk tensioner

combination of additive &

multiplicative principles

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T1

T2

Tension Compensator

Provide constant winding tension,

independent of unwinding tension

32 winding

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