Modern Drafting System:

3-roller, double-apron drafting systems are used exclusively on modern ring spinning machines
used for short staple spinning. They consist of three fluted, driven, bottom steel rollers (a) with top
rollers (b) positioned above them, supported and pressed against bottom rollers (a) by a rocking
support (c) (pressure arm). Since a fiber bundle with only few fibers has to be transported in the
main drafting zone, the main drafting zone is provided with a guide unit consisting of rotating
bottom and top aprons (e).
The front top roller is set slightly forward by a distance of 2 to 4mm relative to the front bottom
roller, while the middle top roller is arranged a short distance of 2mm behind the middle bottom
roller. (Fig-2)
Another roller configuration has been offered by the INA Company in the so-called V Draft
drafting system. In this case the rear top roller is shifted to the rear on the bottom roller. The larger
wrapping arc (a, Fig. 3) results in an additional fiber control zone. However, it can also result in a
wider spread of the fiber ribbon.

Fig. 1 – The drafting system

 Fig. 2 – Section through the drafting system

Fig. 3 – The INA drafting system

 Overhang of the front top roller gives smooth running of the top rollers and shortens the
spinning triangle. This has a correspondingly favorable influence on the end break rate.
 Rubber cots with hardness less than 60 degrees shore are normally unsuitable because
they cannot recover from the deformation caused by the pressure on the top roller while
running.
 Soft rubber cots for top rollers have a greater area of contact, enclose the fibre strand
more completely and therefore provide better guidance for the fibres. However softer cots
wear out significantly faster and tend to form more laps.
 Normally harder rubber cots are used for back top rollers, because the roving which
enters the back roller is compact, little twisted and it does not require any additional
guidance for better fibre control. In the front top roller, only few fibres remain in the
strand and these exhibit a tendency to slide apart Additional fibre guidance is therefore
necessary. Therefore rubber cots with hardness levels of the order 80 degrees to 85
degrees shore are mostly used at the back roller and 63 degrees and 65 degrees at the
front roller.
 If coarse yarns and synthetic yarns are being spun, harder rubber cots are used at the front
roller because of increased wear and in the case of synthetic yarns to reduce lap ups.
Double apron drafting system with long bottom apron
In the double apron drafting system the fiber guidance unit consists of two aprons rotating with
the middle rollers. The top apron must be pressed against the bottom apron with controlled force
in order to provide guidance. For this purpose there must be a gap between the two aprons at the
apron delivery end (tensor gap) that is precisely adjusted to the fiber volume. This gap can be
adjusted by using different spacer plates, shoes, etc.
The top aprons, which are often plastic aprons, are always short. However, the bottom aprons
can be as short as the top aprons (Fig. 2) or quite a bit longer and guided accordingly around
deflecting elements (Fig. 1). The advantage of long bottom aprons over short aprons is that they
are easy to replace in the event of damage. They are also less inclined to become clogged with
fiber fly.

Fig-2
Fig-1

Double apron drafting system with short bottom apron

Although the short apron arrangement is almost as old as that with the long apron, it is not used
so often. The draw- back of short aprons is that they are more difficult to re- place in the event of
damage. They can also be more inclined to become clogged with fiber fly if holders are used,
and then they run out of true. However, they also have distinct advantages:
 less design effort, i.e. cheaper;
 structural components under the drafting system, such as deflectors, cleaning devices and
guides, can be dispensed with, and accessibility under the cylinders is improved;
 They can be placed closer to the front rollers, which improves fiber control.
Method of applying pressure:
The following way load or weighting is applied at the nip point of bottom roller by top roller.
 Spring loaded or Pendulum arm.
 Pneumatic weighting
 Magnetic weighting
With pneumatic loading system, the total pressure applied to all top rollers is obtained by simple
adjustment of the pressure in the hose using pressure reducing valve. Moreover the rubber cots
will not get deformed if the machine is stopped for a longer duration, because the pressure on top
rollers can be released to the minimum level.
The fibre strand in the main drafting field consists of only a few remaining fibres.
There is hardly any friction field and fibre guidance provided by the rollers alone is inadequate.
Special fibre guiding devices are therefore needed to carry out a satisfactory drafting operation.
Double apron drafting arrangements with longer bottom aprons is the most widely used drafting
system in all the modern ring frames.
In double apron drafting system two revolving aprons driven by the middle rollers form a fibre
guiding assembly. In order to be able to guide the fibres, the upper apron must be pressed with
controlled force against the lower apron. For this purpose, a controlled spacing (exit opening),
precisely adapted to the fibre volume is needed between the two aprons at the delivery. This
spacing is set by "spacer" or "distance clips "Long bottom aprons have the advantage in
comparison with short ones, that they can be easily replaced in the event of damage and there is
less danger of choking with fluff.
Spindles and their drive have a great influence on power consumption and noise level in the
machine The running characteristics of a spindle, especially imbalance and eccentricity relative
to the ring flange, also affect yarn quality and of course the number of end breakage. Almost all
yarn parameters are affected by poorly running spindles. Hence it should be ensured that the
centering of the spindles relative to the rings is as accurate as possible. Since the ring and spindle
form independent units and are able to shift relative to each other in operation, these two parts
must be re-centered from time to time.

Pneumatic drafting system Pendulum arm/Spring Loaded

1. Loaded by pneumatic pressure i.e.
compressed air 1. Loaded by spring
2. Uniform pressure is applied to all drafting 2. Applied pressure in all drafting zones is
rollers not uniform
3. Consistent yarn quality is achieved 3. Consistent yarn quality is not achieved
4. Modern drafting system 4. conventional system
Apron:
Rubber Apron is made of synthetic rubber material, with excellent wear-resistance/oil-
resistance/ageing-resistance and smooth surface. In addition, it is of good stability, flexibility &
wide application. It is used in drafting system of ring frame and some other modern drafting
system in spinning machine. It contains cradle for guiding its direction of length.

Rubber cot Roller:

It is one type of synthetic rubber material which is used in top rollers of ring frame drafting
system. The rubber cots also used on drawing frames, combing machines & spinning frames. Its
hardness can be varied. The hardness of rubber cots is expressed by degree. Generally harder
cots are used in the back rollers and softer rollers are used in front rollers.

Hardness ranges are given below-

 Soft: 60° to 70° Shore
 Medium: 70° to 90° shore
 Hard: above 90° shore
80° to 85° shore are mostly used at the back roller and 63° to 65° shore at front roller.
Spindle:
The spindle is the main part of a ring frame which helps in twisting, winding simultaneously.
Sometimes, spindle referred as ‘heart of spinning’. It hold the bobbin, somewhat loosely but tight
enough to prevent slippage.

Functions of spindle:
 Twisting and winding is performed by spindle.
 It holds the bobbin.
 The capacity of ring frame is mainly determine by the number of spindle.

Different parts of spindle:

 The parts of spindle are given below:-
 Spindle blade
 Wharve
 Bolster
 Lock
 Bearing
 Bolster cage
The last three parts help the spindle to fix at the right place and work properly.

Ring:
The ring are made of low carbon steel i.e. soft steel or ceramic in the form of a bar which
modeled into ring shaped either by bending and welding or by pressing by means of dies and
then the stock is given the desired projection term as ring flange.

Function:
There are some important functions of ring. These are given below:-
 Ring guides the circular run of the traveler.
 It also helps in twisting by means of running of the traveler.
 It also acts as a track of traveler.

Optimal running conditions depend upon:

 Materials of the ring and traveler
 Surface characteristics
 The form of the both elements
  Wear resistance
 Smoothness of running
 Running-in conditions
 Fiber lubrication.

Classification of ring:
A) According to origin or element:- i. Metallic ring, ii. Ceramic ring
B) According to number of flange:- i. Single flange ring, ii. Double flange ring
Single sided ring (Fig.2a) must be replaced by new ones after they are worn out; a double sided
ring (Fig.2b) worn on one side and can be turned over and used on the second side. The later
serves for mounting of the ring while the first side is acting as traveller guide.
Flange:
The path of traveler on the ring is called flange. It may be single or double.

Flange width:
The term flange width express the difference the outer diameter and inner diameter of a ring.
Flange width is expressed in flange no.

Flange width= (Flange no. + 3)/32 inch

Flange no. Flange width (mm)

1 3.2
1.5 3.6
2 4

Rings are available with the following internal diameters (in mm):
36, 38, 40, 42, 45, 48, 51, and 54.

The following materials are used in Ring

 Flame – or induction hardened steel, to some extent;
 Nitride steel; this is now rare since ablation can arise owing to the high surface
hardness;
 Carbon nitrided steel; this is the most common;
 Chrome steel; this is found more rarely.
Required features for the ring
 Best quality raw material
 Good, but not too high, surface smoothness
 An even surface
 Good, even surface hardness, higher than that of the traveller
 It should have been run-in as well as possible (optimal running-in condition)
 Long operating life time
 Correct relationship between ring and bobbin tube diameter
 Horizontal disposition
 It should be exactly centered relative to the spindle.
Traveler:
Traveler is the most tinny and simple mechanical element in ring frame which carries the most
important function like simultaneous twisting, winding, thread guide etc.

Function of traveller:
Traveler does some important in ring frame. These are mentioned below:-
 Twisting on the drafted strand of fibre.
 Winding of the yarn on the bobbin.
 Maintain winding tension of the yarn by the frictional resistance between the ring and the
traveler.
 It acts as a guide for yarn on the way to be wound on the bobbin.

Parts of traveller:
There are three parts of a traveller. They are given below:-
 Bow
 Horn
 Flange
Types of traveller:
Travelers can be classified into following two ways:-

A) According to shape:-
 C – traveller
 Elliptical traveller
B) According to the X-section of wire:
 Round traveller
 Flat traveller
 Semi-circular traveler
(a) C traveler; (b) flat traveler (standard traveler); (c) elliptical traveler; (d) N traveler

Traveller Feature:
 Generate as little heat as possible
 Quickly distribute the generated heat from the area where it develops (the
contact surface) over the whole volume of the traveller
 Transfer this heat rapidly to the ring and the air
 Exhibit high wear resistance; but
 Be somewhat less hard than the ring, because the traveller must wear away in
use in preference to the ring.
Factors considered for selection of a traveler:
1. Yarn count: Higher the yarn count, lower will be the traveler weight.

2. Spindle Speed: If the spindle speed is high, then the yarn tension will be high. So lighter
traveler should be used to minimize tension.

3. Ring dia: For same spindle speed and count, with the increase of ring diameter yarn tension as
well as frictional area increases. So traveler should be lighter.
4. Empty bobbin dia: When empty bobbin dia decreases, winding angle decreases resulting a
higher yarn tension. So a light traveler should be used.

5. Lift of bobbin: If the lift of bobbin increases yarn tension will be higher. So traveler weight
should be less.
Some important information:
 Usually used ring diameter: 33, 36, 38, 40, 42, 45 mm
 Ring cup diameter: Empty bobbin dia. = 2:1 or 2.5:1
 bobbin length = 5 x Ring Diameter
 Bobbin lift = Bobbin length – 20mm
Traveller Count:
Traveler no. expresses the wt. of traveler. It can be done in two ways –
a) Indirect system: Here the unit is 10 travelers. If 10 travelers weight is 10 grain then, the
no. is one. If it is 11 grain then no. is 2 and so on. Again, if the wt. of 10 travelers is 9
grain then, traveler size is 1/0 or 1-0. If it is 8 grain then the size is 2/0 or 2-0 and so on.
That is, if the no. is less, then the traveler is light. In practice, travelers are available
from no. 1 to 10 (Heavy traveler) and reversely 1/0 to 20/0 (Lighter). Commonly, for
finer yarn light traveler is used and for coarser yarn heavy traveler is used.
b) Direcect system: Here every individual traveler is weighted. Heavy wt. indicate heavy
traveler

Recommended traveler no. for various yarn counts:

Count (Ne) Traveller No.

16 2
20 1-2/0
30 3/0-4/0
40 6/0-8/0
50 10/0-12/0
60 13/0-15/0
80 16/0-19/0
100 19/0-20/0
A basic distinction is made between three groups of spindle drive:
 tape drive
 tangential belt drive and
 Direct drive.
Tape drive is in turn sub-divided into:
 individual spindle drive and
 group drive
And direct drive into:
 Mechanical and
 Motorized direct drive.