16-08-2014, 12:04 PM
Project Report On Prevention of Faults on Wool Fabrics by Application of Cold Sizing
Prevention of Faults.pdf (Size: 368.88 KB / Downloads: 44)
Abstract
Mechanical faults on woolen fabrics are often the result of
insufficient mechanical properties of wool warp that must be
achieved to ensure smooth process of weaving.
Conventional sizing is not appropriate for the preparation of
wool yarn for weaving because of sensitivity of wool fibers
to high temperatures. For that reason, wool warp is mostly
prepared by using the waxing procedure whereby
protruding fibers on the yarn surface are smoothed. In this
way, its friction and elongation properties are improved.
Another option is a cold sizing. It is a process, which aims to
achieve the effect of conventional sized warp, but without
the use of high temperatures.
Cold sizing has been proved to be a good solution for wool
warp sensitive to dynamic stresses during the weaving
process. This paper describes advantages of the cold sizing
procedure to warp waxing. The number of end breakages on
the weaving machine, lengths of a faulty place in the thread
marked in the inspection room of the weaving mill, and
times spent for manual retouching are compared. The type
of fabric, for which an increase in costs for cold sizing is
justified, is also determined.
Introduction
In the weaving process, the warp is subjected to
various stresses such as cyclic tensioning, bending,
friction with machine parts, and thread-to-thread
friction during weft beat-up etc. In order for the
weaving process to run trouble-free, warp threads
should meet certain criteria related to appropriate
mechanical properties. First, it applies to strength,
friction properties of yarn and elongation properties.
Nowadays, market requirements on fabric
manufacturing become increasingly demanding. A
demand for woven fabrics with as small masses per
unit area as possible increases permanently, resulting
in the use of yarns with very fine counts. Thus, criteria
Fabric Faults Caused by Inappropriate Physical Mechanical Properties of the Warp Yarn
The production of fabrics with lower weight
necessitates the production of finer and more
demanding yarns. Ply yarns with sufficient strength
and compactness, ensuring a trouble-free weaving
process, replace unconventional single yarns to be
used as warp yarns. The cause is an evident difference
in the fineness and price of ply and unconventional
ring-spun yarn. Although yarn properties have been
taken into account in case of developing modified
spinning methods, only minimal requirements can be
infrequently achieved. Limited values of yarn
processability are a frequent cause of disturbances in
the fabric production. The replacement of finer ply
yarns with single yarns sometimes leads to the
reduction of machine efficiency and fabric quality
Experimental
Yarn processability and efficiency of waxing and
sizing wool warp were tested, and the test results were
compared. The warp was warped on the section
warping machine Benninger BEN TRONIC, and the
yarn was from the same batch. About 400 m warp was
warped for about 380 m fabric. The first part of the
warp (180 m) was waxed with a standard wax agent,
while the other part of the warp (220 m) was sized
with a cold sizing agent. The conditions of the
weaving process were the same (Table 1) on the same
Sulzer G 6200 weaving machine.
Warp Waxing
A non-ionizing liquid agent composed of
polyglycol ether and fatty alcohol ethoxylate was
used for waxing. The agent has antistatic properties;
additionally, it is soil resistant and rinsable in the
washing process in the wet finishing. The agent is
poured into the wax container of the waxing unit.
During rewinding from the warp cylinder to the
weaver’s beam, it is applied directly by the
application roller.
Cold Sizing
The cold sizing agent is, by its composition, a
synthetic copolymer, based on a diluted solution of
polyvinyl alcohol (PVA), is water soluble and can
be easily rinsed from the fabric using a neutral
aqueous solution at the temperature 40°C, as well it
is applied very simply when the warp is rewound
from the warp cylinder to the weaver’s beam, as in
case of waxing, without warming and additional
drying as in case of conventional sizing. After the
application of this agent, the warp threads do not
cling to each other and it is not necessary to
separate them. The disadvantage of this agent is
that it very quickly sediments into the upper liquid
layer and the lower gelatinous layer when the
container remains open. Therefore, the size should
be stirred before it is repeated utilized. The sized
warps should not be allowed to rest for a longer
period.
Discussion
In case of the warp waxed with the standard waxing
agent, one end breakage occurred per 6039 picks,
meaning that there was one machine standstill each
13.2 minutes due to an end breakage (Table 3 and
Figure 5). In case of the sized warp, the number of end
breakages was significantly lower. One end breakage
occurred per 14417 picks, i.e. converted into time,
there was a machine standstill each 31.6 minutes due
to an end breakage, 2.4 times lower than in case of
weaving the waxed warp. If it were considered that it
would take the weaver about 3 minutes to eliminate
an end breakage and that the working time lasted for
7.5 hours or 450 minutes, in case of the waxed warp, it
took the weaver 83.3 minutes to eliminate an end
breakages, while in case of the sized warp, it cost 39.0
minutes to eliminate an end breakages. In the latter
case, it will not only take less time to eliminate
mechanical faults for the respective fabric, which is
carried out in the cloth inspection room, but the
weaver can be assigned a larger number of weaving
machines to operate, capable to produce
approximately 2 times more fabric than in the former
case. There are no differences in the number of pick
breakages, which could be expected since the weft did
not undergo any treatment with any agent as well as
high stresses, as the case of the warp.
Tables 5 and 6 as well as Fig. 6 show that the exchange
of faulty threads and cleaning of 174.8 m and 101.0 m
fabric made of the waxed and sized warp cost 470.4
min and 19.2 min, respectively. This means that the
exchange of faulty threads and cleaning of 1 m fabric
made of the waxed warp needed 2.7 min, while it took
0.2 min to exchange faulty threads and clean the same
fabric length for th
Conclusion
The warping, the key process prior to weaving
depends on quality of fabric production in further
processing stages. Faults that occur during sizing are
almost incorrigible in the downstream processes. Thus,
warping is one of very important stages in fabric
manufacturing confirmed by a sentence "well
prepared is half woven". Sectional warping is among
other things used for wool yarns which have usually
been waxed and not sized up to now. Nevertheless,
cold sizing is required due to market demands for
higher quality and more lightweight fabrics. Waxing
does not satisfy new products and cold sizing is
applied.
This paper proves the justification of using cold sizing
for lightweight wool fabrics made of finer warp ply
yarns. By sizing, the efficiency of weaving machines
has increased, enabling a higher machine assignment
per operator. Likewise, the productivity of the
operator cleaning grey cloths increases too. Switching
from waxing to sizing the warp does not mean that the
sectional warper should be rebuilt. Thus, the same
sectional warper can be used either for waxing or for
cold sizing, depending on individual fabric styles.
Further research is necessary to optimize cold size
pick-up based on size recipes and selection of sizing
agents.