This project work covers the different technical and theoretical aspects, related literature
reviews, experimental findings and their both tabular and graphical representations,
technical explanations and result analysis from our work termed Impact of different
clearing limits of yarn clearer on yarn quality and productivity. For all known spinning
methods of today it is necessary to have a yarn monitoring system in the last production
process of the spinning mill, which stops the production position if disturbing faults
occur. The machine must automatically remove the faults and replace it by a splice. The
spinning process is not a perfect process and can produce imperfections. Another source
for irregularities in ring spinning is the availability of flies in the air which are frequently
spun into the yarn and accumulations of fibre fragments and dust at yarn guiding
elements. In ringframe, all fibre and yarn guiding elements, ring traveler, pressure rollers,
belts and spindles can contribute to yarn faults, particularly if there are defective.
Therefore, one important rule of modern quality management cannot be implemented
completely: Preventive actions rather than corrections afterwards!
With the help of yarn clearer such as Uster Quantum 2, Loepfe Zenith etc. we can remove
different types of prominent yarn faults thus improving quality of yarn.
To study about different yarn clearing systems and clearing limits from literature.
To analyze various types of yarn faults.
To process ring yarn of same specifications under three different clearing limits in
Uster Quantum 2 and observe the resultant cut data.
To analyze yarn quality and characteristics before and after winding.
To study the effects of the three different yarn clearer settings on productivity and
wastage generation in winding machine.
Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 2
Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 3
2.1 Yarn clearer
The device which is used to remove faults (thick places, thin places, foreign matter) from
the yarn is known as yarn clearer. Yarn clearing improves the quality of the spun yarn and
hence of the cloth made of it.
Yarn clearing is usually part of the yarn winding process. The yarn from a number of
spinning bobbins, called 'cops', is wound on to larger packages called 'cones' for
subsequent processing into fabric. During the winding the yarn was traditionally passed
through the narrow slit in a steel plate of a yarn clearer or slub-catcher. The object was to
catch thick places, or slubs, which occurred when the spinning process suffered an
aberration, and to prevent them being woven into the fabric to present unsightly faults.
In modern textile industry, after detecting the faults, the clearer cuts the faulty pieces
from the yarn, and after that the piecing device joins the cut ends. 
2.2 Types of yarn clearer
There are two types of yarn clearer
1. Mechanical type
Conventional blunt type
Serrated blade type2. Electronic type
2.2.1 Mechanical type
A mechanical clearer maybe as simple as two parallel blades. The distance between the
blades is adjustable to allow only a predetermined yarn diameter to pass through. A
thicker spot on the yarn (slub) will cause the tension on the yarn to build up and
eventually break the yarn. Consequently, this type of device can only detect thick places
in the yarn. 
2.2.2 Electronic type
Electronic yarn clearers ensure excellent clearing to be obtained with minimum
mechanical stress on the yarn. In order to be able to monitor and to evaluate thick and
thin places as well as deviations from the desired yarn count, the thickness of the yarn
must be converted into a proportional electrical voltage. The course of voltage is called
Impact of different clearing limits of yarn clearer on yarn quality and productivity Page 4
yarn signal. This conversation is carried out either with the sensor of the capacitive
measuring principle or with the sensor of the optical measuring principle.
The capacitive measuring principle
The electrical measuring condenser (1) forms the sensor for the capacitive monitoring of
the yarn mass. This is done by two parallel metal plates, the electrodes. In the space in
between (2), the two electrodes build an electrical field when putting on an electrical
alternating voltage (3).
Figure 2.1 Capacitive sensor
If a yarn (4) is brought into this field, the capacitance of the measuring condenser is
changed. From this change, an electrical signal, the yarn signal is (5) is derived. The
change in the capacitance depends, besides of the mass of the yarn and of the dielectric
constant of the fibre material is used, on the moisture content of the yarn.
With the capacitive measuring principle, the yarn signal corresponds to the yarn cross-
section and yarn mass respectively, which is located in the measuring field. Changes of
the yarn mass cause a proportional change of the yarn signal.
The optical measuring principle
The infrared light source (1) and the photocell (3) represent the sensor for the optical
monitoring of the yarn thickness. The infrared is light is scattered by a diffuser (2) in the
light field and reaches the photocell (3). The photocell emits a signal, which is
proportional to the amount of light.
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Figure 2.2 Optical sensor
If a yarn (4) is brought in the light field, parts of the light will be absorbed by the yarn.
The amount of light, which hits the photocell, is smaller. From this change, an electrical
signal, the yarn signal (5) is derived.
With the optical measuring principle the yarn signal corresponds to the diameter of the
usually round yarn, which is located inside the measuring field. Changes of the yarn
diameter cause a proportional change of the yarn signal. 
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Table 2.1 Comparison between capacitive and optical principle
Property Capacitive principle Optical principle
Yarn signal Corresponds to the Corresponds to the diameter
mass/cross section of the of the yarn and the visual
yarn or the number of fibres impression.
in the measuring field.
Effective measuring field The current yarn signal is The current yarn signal is
length: different measuring the mean value of the piece the mean value of the piece
field lengths influence the of yarn which is located in of yarn which is located in
monitoring of very short the measuring field. the measuring field. Length:
yarn faults. Length: 7 mm 3 mm
Evaluation of the yarn fault
Normal yarn fault The fault is evaluated with The fault is evaluated with
the full increase of the the full increase of the
cross-section in percent. diameter in percent.
Voluminous, visually large As the number of additional The very voluminous yarn
appearing yarn fault fibres is not extremely high, fault absorbs a lot of light.
this yarn fault is considered Therefore, the fault is
as relatively insignificant. considered as significant.
Short yarn faults, length: 3 The increase of the diameter The fault is evaluated with mm
of this short fault is the full increase of the
averaged over the whole diameter.
measuring field length. The
fault is only evaluated as
half of the size.
Very compact yarn fault The fault is evaluated with Compact yarn fault absorbs
the full increase of the small amount of light.
cross-section. Due to the Increase of the diameter is
The distance between two higher number of fibres considered as insignificant.
white lines is 1 cm. thick place absorb more
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2.3 Comparison between mechanical and electronic type
Electronic clearer are more sensitive than mechanical clearers.
In case of mechanical clearers there is abrasion between yarn and clearer parts
but in case of electronic clearers there is no such abrasion.
Mechanical clearers do not prevent soft slub from escaping through clearer
where as electronic type does not allow passing of any types of faults.
Mechanical type does not break the thin places and the length of the fault is not
Mechanical clearer are simple and easy to maintain while the electronic clearers
are costly and requires high standard of maintenance. 
2.4 Development of yarn clearer
In 1960 Zellweger Uster launched the first electronic yarn clearer, the USTER
SPECTOMATIC. With one single, central setting it could be determined, from