2. Definitions
A textile yarn is an assembly of a substantial
length and relatively small cross – section of
fibres and/or filaments with or without twist.
Yarns can be can be classified as;
Spun staple fibre yarns – Yarns in which
staple fibres are assembled and bound together
by various means e.g. Twist insertion and use of
adhesive
Continuous filament yarns – Yarns
produced from continuous filament fibres
02/12/2013 88
3. Staple FibreYarns
A staple spun fibre yarn is a linear assembly of fibres
held together by the insertion of twist to form a
continuous strand, small in cross-section but of any
specified length.
Staple spun fibre yarns are used in processes such as
knitting, weaving and sewing
Staple fibre yarns can also be classified according to;
Fibre length:
Short staple yarns: made of fibres of length less than
60mm
Long staple Fibres : made of fibres of fibre of length
greater 60mm
02/12/2013 89
4. Staple FibreYarns
Yarn Construction i.e.They way a yarn is made
Single yarn: One yarn made up of twisted fibres
Plied or folded yarns : Made of two or more single yarns
twisted together
Cabled yarns: Made of two or more plied yarn twisted
together
FancyYarns:Yarns having deliberately produced
irregularities
Spinning System Used
Ring SpunYarns:These are produced on the ring spinning
machine
Rotor spun yarn: Made on rotor spinning machine
02/12/2013 90
5. Staple FibreYarns
Friction Spun Yarns: Made on friction spinning machine
Wrap spun Yarns: made of a parallel bundle of staple
fibres bound in a compact structure by a continuous
filament yarn. Staple fibre yarns can also be used.
Core Spun Yarns: Yarns having a central core wrapped
with fibres e.g. Filament core wrapped with fibres
Fasciated yarns: Yarns made up of parallel bundles of
fibres bound into a compact structure by surface
wrappings at regular intervals
02/12/2013 91
8. Yarn Dimensions
As with fibres, It is not easy to measure the diameter of
a yarn.
Yarns have different dimensions/thickness depending on
the end uses and how the yarn is made.
It is thus accepted to express the yarn thickness using
the yarn counting systems i.e. in terms of its linear
density
There are two main Systems used to indicate the yarn
linear density namely direct system and indirect
system
02/12/2013 93
9. Direct System
In this system, the fineness (linear density) of a yarn is expressed as
the mass of a yarn per unit length.
Linear density = mass of a yarn/length of a yarn
In this system, the lower the linear density, the finer the yarn
The direct system is called the Tex system. Units used in this system
and their conversion are given below.
1Tex = 10 Decitex (dTex),
1 kilotex (kTex) =1000Tex
1 dTex = 0.9 Denier
1Tex = 9 Denier
1Tex = 1000Millitex
This system is used internationally i.e. it is a universal system
02/12/2013 94
10. Indirect System
In this system the yarn thickness is expressed as the length
of a yarn in a unit mass.
Linear Density = Length of a yarn/mass of a yarn
In this system, the yarn can be measured in;
Metric count (Nm): Number of 1000 lengths in a
kilogram. i.e. The number of kilometres in one kilogram
of a yarn.
Cotton Count (Ne): Number of 840 yard Hanks of a yarn
in one pound.
02/12/2013 95
11. Indirect System
Conversion factors:
Cotton count (Ne) = 590.5/Tex
Metric Count (Nm) = 1000/Tex
Note:
For a given yarn linear density, the number of fibres in
the cross-section of a yarn can be calculated if the fibre
linear density is also known.
Example:The linear density of a yarn is 20Tex and the yarn
is made of fibres of a linear density of 0.5dTex. Find the
number of fibres in a yarn cross – section.
Formula: Number of Fibres = linear density of yarn/linear
density of fibres
02/12/2013 96
12. Yarn Production Methods
There are two main systems of yarn production
namely ring spinning and open end spinning
systems.
Ring spinning is done on ring spinning frame
(machine)
Open end spinning system including systems such
as rotor spinning, friction spinning, vortex spinning,
wrap spinning
Several systems of open end spinning exist but
only rotor and friction spinning systems have been
commercially successful, with rotor spinning
dominating the market.
02/12/2013 97
13. Ring Spinning Frame
The ring spinning frame consists of the drafting system,
the spindle, the yarn guide and the ring rail.
The rings are built in the ring rail.
The yarn guide, the ring and the spindle share the same
vertical axis.
The yarn from the roving passes through the drafting
system, where it is reduced to a lower linear density.
The roving is gradually reduced as it progresses from
the back to the front roller.
The back roller draft is normally set at 1.25 which is
much lower compared to the front roller draft
02/12/2013 98
21. Ring Spinning
The twist is inserted by the traveller as it rotates
around the ring,
Twist insertion rate depends on the diameter of
the bobbin – any variation of twist?
As the traveller rotates the twist is inserted in the
balloon length and propagates to the yarn guide
and to the nip of the front rollers – creating a
spinning triangle!
The package on the tube is built by up and down
movement of the rail along the bobbin
Increasing yarn tension results to excessive
breakage
02/12/2013 101
24. Db
Nt
Ns
Bobbin
Traveller
(Ns - Nt) π Db = Vd
Ring
VdSpindle speed =
Bobbin speed
Twists/Meter t = Nt / Vd
Rotation of traveller
Inserts twist
25. Vd = (Ns - Nt) π Db
Vd / (π Db) = (Ns - Nt)
Vd / (π Db) + Nt = Ns
Nt = Ns - Vd / (π Db)
During production:
Ns, Vd do not change
Db increases
Nt increases
26. Twists/Meter t = Nt / Vd
Nt = Ns - Vd / (π Db)
Yarn twist increases during production
t = Nt / Vd
= Ns / Vd – 1 / (π Db)
T ≅ Ns / Vd
Small value
Usually ignored
27. Twists/Meter
t = Ns / Vd
Vd = Ns / t
Faster spindle speed: faster production
More twist: slower production
28. Production rate (kg/h):
NE
tex
Vd ××××× 60
1000
1
1000
NE
K
tex
Ns ×××××× 60
1000
11
1000
5.1
textK =
t
Ns
Vd =
tex
K
Ns
=
K
texNs
=
tex
K
t =
30. Machine efficiency is affected by:
End breakage rate
Package size
Yarn tex
Spindle speed
End breakage rate is affected by:
Machine condition
Yarn strength (evenness, fibre, twist, tex)
Yarn tension (spindle speed, balloon size,
ring & traveller)
31. Package needs to
Have maximum yarn
Be free from yarn entanglement
Be stable
Be even in density and yarn tension
32. Main layer
(slow lifting of ring rail)
Ring Package (Cop)
Tube
Cross layer
(fast descending)
Package building
motion
33. Ring Spinning
The increase of yarn balloon between the traveller
and the yarn guide is the result of yarn tension
increase
This increases at increased traveller speeds and type
Proper selection of the traveller weight for a
particular yarn linear density and yarn type is
crucial!
For yarn counts in the range of 20Tex to 30Tex,
traveller weights of 3mg/Tex are recommended, and
2.6mg/Tex for higher count
A new ISO standard specifies the appropriate
traveller number for a given yarn linear density
02/12/2013 102
34. Traveller weights recommended by ISO
standards
Cotton Synthetic fibres
17 45 56
20 56 71
24 71 90
30 90 100
36 100 112
02/12/2013 103
Linear density Traveller Number
36. Draft values for cotton and synthetic
fibres
Material Draft
Carded cotton Up to 35
Medium fineness combed cotton up to 40
Fine cotton Up to 45
Synthetic fibres Up to 45
02/12/2013 105
• Accurate and precise drafting arrangement (rollers)
is required;
• Otherwise it can cause uneven yarn and thus
contributing to end breaks.
• Higher drafts contribute to reduction in yarn quality.
37. Minimum Number of Fibres inYarn
Cross Section
Combed cotton 33 fibres
Carded cotton 75 fibres
Carded synthetic fibres 50 fibres
02/12/2013 106
• Many fibres are required in the cross section for cotton
than in synthetics since most cotton fibres are short
compared to synthetic fibres.
• The minimum number of fibres therefore sets the
spinning limit.
38. Roving Production Calculation Example
Given:
Spindle speed: 1000 rpm
Roving linear density: 400 tex
Drafting roller diameter: 25 mm
Drafting roller speed: 250 rpm
Bobbin tube diameter: 5 cm
Full bobbin diameter: 10cm
Calculate:
Roving twist factor
Initial bobbin speed (empty bobbin)
Bobbin speed when bobbin is full
39. Ring Spinning Production Calculation Example
Given:
Spindle speed: 18,000 rpm
Yarn linear density: 36 tex
Twist factor: 36 turns⋅cm-1⋅tex1/2
Machine efficiency: 90%
Production rate: 100 kg/h
Calculate:
The number of spindles required.
The production rate of the machine
for a 9 tex yarn, all other conditions
remain the same.
