This document discusses drafting systems used in yarn manufacturing. It begins by defining drafting and its importance in the design process. It then describes two main types of drafting systems - spring loaded and pneumatic. Details are provided on the components, setup, and adjustment of these systems. The document further classifies drafting systems into regular systems without aprons and those with single, double, or multiple aprons. Examples are given for each category. In closing, roller drafting systems are identified as the most commercially successful due to attributes like versatility, simplicity, reliability, and ability to handle various fiber types and counts.

1. Yarn Manufacturing-II (TE312)

2. Name: Niloy Saha
ID: 162-23-4732
Sec: B (Eve)
Name: Mehedi Hasan
ID: 162-23-4731
Sec: B (Eve)

3. Drafting is the creation of a drawing or other graphical representation of a building,
mechanical device or other structure for the purposes of determining how the device should
be created. Drafting is used as a part of the design and fabrication processes. Drafting can
be done by hand or using specially designed computer programs and mechanical drawings.
Drafting arrangement is the most important part of the machine. It influences mainly
evenness and strength The following points are therefore very important
 drafting type
 design of drafting system
 drafting settings
 selection of drafting elements like cots, apron, traveler etc.
 choice of appropriate draft
 service and maintenance

4. There are commonly two types of drafting system are used in
ring frame:
Spring loaded drafting system or pendulum arm.
example: SKF PK 2025 or Texparts 2035
Pneumatic drafting system: SKF PK 3025

5. Each compensating roller is
seated in a bearing slide
(1, 2, 3); these are infinitely
adjustable relative to each
other. A spring (4,5, 6) –
sometimes two on the front
roller – presses the top roller
against the bottom roller. In the
case of SKF the loading
pressure can simply be
adjusted in three stages by
means of a tool. Colored marks
indicated the set loading stage.
Fig. – SKF PK 225 rocking support

6. The loading support is stamped from steel sheet and is
mounted on a continuous hexagonal section tube behind the
rollers. The tube contains the compressed air hose
connected to a central compressor unit. Three top roller
holders mounted on two bearing slides are accommodated
in the loading support itself. The two bearing slides form a
double lever system. Depending on where a pin is inserted
in one of the three holes as the pivot at „m“, the total
pressure coming from the compressed air hose and acting
on the entire pressure arm via a cam is applied more
strongly to the back roller or the two front rollers. Pressure
can also be distributed differently between the two front
rollers via a second pin/hole system in the bearing slide of
these two rollers at „n“.
Fig. 13 – Pneumatic loading by Rieter

8. Drafting system can be broadly classified under two
heads namely –
1. Regular drafting system without apron. And
2. Drafting system with apron.
The system with apron can again be classified into
three groups –
1. Single apron system.
2. Double apron system. and
3. Multiple apron system.
Example of regular drafting system without apron –
a. Conventional three roller system.
b. Improved system.
c. H and B four rollers long draft system.
d. 5 over 4 roller systems.
Example of single apron drafting system –
a. Saco – Lowell. Both systems.
b. Saco – Lowell. Shaw system.
c. Saco – Lowell. Z system.
d. Versatex LS system.
Example of double apron drafting system –
a. Casablancas double apron system.
b. Casablancas “L” system with flexible bar.
c. Saco – Lowell thread rollers duo-Roth system.
d. SKF pendulum top arm weighting system. And
Example of multiple Apron drafting system –
a. Casablancas “N” system.
b. Nittoh’s Semi-super high draft system.
c. OM – S super high draft system.

9. Commercially, there are various methods to draft the textile fibrous material like roller
drafting system applied at ring spinning, speed frame and draw frames etc, aero dynamic
drafting functional at rotor spinning, electro mechanical drafting, frictional drafting, etc. Out
of these techniques, roller drafting system is
the most commercially successful one due to its high versatility, simple design and
construction, high reliability and can handle variety of fibres and a wide spectrum of count
range can be spun.
Fig : 3/3 roller drafting system at ring spinning

10. In the Rieter comber, the sliver table
leads to a vertically inclined 3-over-
3 drafting arrangement (Fig. 56),
sometimes with an additional
pressure bar in the main draft zone.
The rollers form two drafting zones.
Break draft as well as main draft
distances and the amounts of draft
are variable. The overall draft lies
between 9 and 16. At the delivery
end of the drafting arrangement a
trumpet collects the discharged web
and guides it, with additional
compacting, to the delivery rollers. Fig. 56 – The drafting arrangement of the Rieter
combers
Fig. – Sketch of the drafting arrangement
of the Rieter E 65/75 combers

11. 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.
Fig. – Long bottom apron

12. The effective drafting force can be represented by the curve form shown in Fig. 45. Up to point
m, at which the fibers begin to slide apart, the curve climbs steeply. This is the straightening and
extending stage. From point n onwards, by which stage many fibers are already sliding, the
curve falls slowly with increasing draft. The reduction of the drafting force with the increasing
extent of draft is easy to explain – there is a continuously declining number of fibers to be
accelerated, i.e. to be drawn out of the slowly moving strand, since a higher degree of draft
implies fewer fibers in the cross-section.
Fig.– The forces acting on fiber (f) during drafting Fig. 45 – Drafting force diagram; F, magnitude of
the drafting force. D, magnitude of the draft