CHAPTER V
YARN QUALITY PARAMETERS OF IMPROVEDCHARKHA
Yarn Quality plays an important part in determining the working
of the loom, appearance of the cloth woven and ultimately the price of
cloth. Better the yarn quality more is the yarn demand for the yarn
and higher will be the market price for good quality yarns. SITRA has
evolved quality standards or Norms for the cotton yarns spun. The
yarns that are produced on the different charkhas have been
ultimately compared for quality against SITRA Norms to see we ,ther
they meet the quality requirements. The quality particulars have been
evaluated for each count that is spun on the charkha
5.1 Yarn Quality Parameters To Be Tested andEvaluated
Yarn samples were spun on all the 3 types of spinning
machines namely 8 Spindle Hand Operated Charkha, 8 Spindle
Motor Operated Charkha and 16 Spindle Improved Charkha. The
roving bobbin of 0.90 hank was taken to Spin 10s' and 33s Nm and
1.20 hank roving was used to spin 64s and 72s Nm. The Spindle
speeds were kept at 5500 rpm and 6500 rpm. Only when the speed
exceed 6500 rpm and above the yarn quality deteriorated due to
excessive end breakages and it was not practical to run the
machine at speeds exceeding 6500 rpm as the stoppage time of the
machine to repair broken threads has become very high. A total of
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20 readings for each count was taken to get the average yarn
quality characteristics like CV% of TPI, U%, Thin place/km, Thick
place/km, Neps/km, Rkm values, % of Elongation and Hairiness
Index. The quality particulars of the yarn have been tested and the
results have been analyzed. It can be seen from the test results that
there is vast improvement in yarn quality, obtained with yarn
produced on improved charkha and the quality levels are
comparable with SITRA* norms for mill made yarn of similar counts.
There is also appreciable improvement in yarn quality when shifts
are made from Hand-Operated Charkha to Motorized charkha and
16 Spindle Improved Charkha for all counts. This is because of the
uniform twist flow to the yarn during charkha spinning as the
spindles are driven by motor; this ensures constant speed of
rotation of the machine parts. This stabilization of TPI has yielded
better yarn quality.
5.2.0 Yarn Quality Characteristics
5.2.1 Yarn Quality Characteristics Of 10s Nm spun on charkhas
(5500 rpm and 6500 rpm)
10s Nm** count was spun on the selected charkhas with 5500
rpm and 6500 rpm of spindle speeds .The quality particulars of 10s
Nm count are obtained from 8 Spindle Hand Operated Charkha, 8
Spindle Motor Operated Charkha and 16 Spindle Improved Charkha
are compared with SITRA norms.
* SITRA - South India Textile Research Association, Coimbatore
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The TPI (Twist Per Inch) 10.0 is given to the yarn, which is kept
constant for all the charkhas.
The trial was taken on 8 Spindle Hand Operated Charkha, 8
Spindle Motor Operated Charkha, 16 Spindle Improved Charkha on
10s Nm at a constant speed of 5500 rpm and 6500 rpm. The yarn
was tested for various parameters like CV% of TPI, U%, Thin
places/km, Thick places/km, Neps/km, Rkm values, Percentage of
Elongation and Hairiness Index. Average of 20 readings for each
quality particulars is given in the Table- 5.1 and 5.2.
5.2.2 CV% of TPI
CV % of TPI affect the working of the yarn in looms. Lower
CV% of TPI is preferable. From the Table -5.1 it is evident that the
CV% of TPI are higher in the yarns made out of 8 Spindle Hand
Operated Charkha, this is because of irregular rotation of handle of
the machine. But the 8 Spindle Motorised Charkha shows 22.4
percentage improvement when compared to 8 Spindle Hand
Operated Charkha. Similarly the CV% of TPI shows 64.2 percentage
improvement in 16 Spindle Improved Charkha when compared with
Hand Operated Charkha and 53.9 percentage improvement when
compared with 8 Spindle Motor Operated Charkha. Even when the
speeds of the charkha were increased to 6500 rpm in Table - 5.2, it
is observed that there is a 30 percentage improvement in CV% of TPI
in the 16 Spindle Improved Charkha.
** Nm - Metric System Of Yarn Numbering
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5.2.3 U%
U % means uniformity index of the yarn tested is lister
evenness tester (Evenness of yarn). The lower U% means better
quality. The U% rating of 8 Spindle Hand Operated Charkha yam
shows higher values than other two charka yarns. The.re is a 15.3
percentage improvement of U% in the 16 Spindle Improved Charkha
when compared with 8 Spindle Hand Operated Charkha in Table-
5.1. However the SITRA norms give lower values. Among the three
charkhas, 16 spindle motor operated charkha yielded better yarn with
16.56 U% for 10s Nm at 5500 rpm.
5.2.4 THIN PLACES/Km
Table - 5.1 indicates the performance of 10s Nm yarn in terms
of thin places (Yarn imperfections). There is a 82.2 percentage
improvement in the yarn imperfections for 10s Nm count at 5500 rpm
of spindle speeds, between hand operated 8 spindle yarn and 16
Spindle Charkha. The 16 Spindle Charkha has given better quality
than SITRA norms. The 8 Spindle Hand Operated Charkha shows
higher values because of the irregular motion of charkha and jerky
rotation of fluted rollers. But, the 16 Spindle Improved Charkha shows
4 percentage improvement when compared with 8 Spindle Motor
Operated Charkha and 82.2 percentage improvement when
compared with Hand Operated Charkha, because of smooth rotation
of drafting rollers and no vibration in improved machine. This has
confirmed that 16 spindle improved charkha has yielded better results
among the charkhas selected for the study. Even at higher speeds of
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6500 rpm in Table - 5.2, there continues to be reduction of thin
places in yarn spun on improved charkha.
5.2.5 THICK PLACES/Km
Table - 5.1 indicates the performance of thick places at 5500
rpm {Yarn imperfections). There is a 48.6 percentage improvement in
the yarn imperfections for 10s Nm count between 8 spindle hand
operated and 8 spindle motor operated. The 16 Spindle Charkha has
given better quality than SITRA norms and the 16 spindle charkha
has yielded better yarn showing an improvement of 53 percentage
over hand operated charkha yarn and 3.5 percentage improvement
over 8 spindle motor operated charkha yarns. Even at 6500 rpm the
thick places have come down in 16 Spindle Improved Charkha in
Table - 5.2. This was because of smooth rotation of drafting rollers
and no vibration in 16 spindle-improved charkhas.
5.2.6 IMEPS/Km
Neps are defined as entanglement of immature fibers into small
ball the size of a pinhead. The neps undesirable both in the yarn and
the fabric as theyappear as fabric defect. These neps do not qbserii'
the dye applied on to the fabric uniformly, because they consist of
immature fibers. Therefore steps are taken to reduce the nep
generation in the spinning process. It is the blow room and the
carding departments that contribute to nep generation. The neps of
16 Spindle improved Charkha shows 3.48 percentage improvement
in yarn imperfections when compared with 8 Spindle Hand Operated
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Charkha however the SITRA norms are better probably because
better collons are used in the mills and latest spinning machinery are
available in the mills. Neps generation has been attributed to mainly
the beater speeds, settings in blow room and carding settings
between feed plate and taker in.
5.2.7 TOTAL IMPERFECTIONS/Km
The total imperfections are the sum of thin place, thick place
and neps/Km of yarn. It goes to show the total yarn defects in a
Kilometer of yarn length. Total imperfections influences loom
performance and over all fabric appearance. Less number of
imperfections in yarn is preferred for better yarn quality. The Table-
5.1 indicates that the total imperfections of 10s Nm count shows 57.1
percentage improvement when compared between 8 spindle hand
operated and 16 spindle improved charkhas and 3.6 percentage
improvement in the 16 Spindle Improved Charkha when compared
with 8 Spindle Motor Operated Charkhas. At speeds of 6500 rpm in
Table - 5.2, it is noticed that the total imperfections in 16 Spindle
Charkha is comparable to SITRA quality standards.
5.2.8 RKM VALUES
Stronger the yarn, higher will be the RKM value. Stronger yarns
produce stronger cloth and spin better without end breakage. The
RKM value of 16 Spindle Improved Charkha shows 31.8 percentage
and 4.8 percentage improvement when compared with 8 Spindle
Hand Operated Charkha and 8 Spindle Motor operated Charkha
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respectively at 5500 rpm of spindle speed for 10s Nm. From this
table, the 16 Spindle Improved Charkha values are higher than 8
Spindle Motor Operated Charkha, because of uniform motor speed
and also less vibration of machine. Here the RKM values of different
Charkhas are equal to SITRA norm values. So the higher RKM
means stronger yarns. Hence, it can be inferred that 16 Spindle
Improved Charkha is giving better yarn strength than ring spun yarns.
It can be obs
