O o d h e a d p u b L i s h I n g L i m I t e d

5.4
Advances, benefits and applications of new
weaving technologies
5.4.1
Structures and constructions in woven wool
fabrics
Because wool is a natural protein fibre, it is difficult to weave with the
consistency associated with a wholly synthetic product, whose composition
can be fully controlled throughout the manufacturing process. Woven wool
fabrics are defined by the three categories of manufacturing machinery for
production of wool yarns: woollen, worsted and semi-worsted. The category
used is determined by the fabric’s intended end use. Worsted is a tightly
woven fabric made by using only long staple, combed wool or wool-blend
yarns. Wool-like fabrics are made from worsted blends. Mohair and other
animal fibres were processed on standard woollen, worsted and semi-worsted
yarn manufacturing machines with occasional modifications to adjust for
variations in fibre length.
Production of worsted (long fibre) yarns for weaving is expensive, due to
the need to two-fold, or ply together, two singles yarns, to create yarns that
survive the stresses of weaving. Typical single yarns break too easily during
weaving. An alternative is to use sized ring spun yarn or use Solospun yarn
made using CSIRO’s Solospun™ attachment. Solospun yarns are robust,
single-ply worsted yarns that withstand the stresses of weaving (or knitting).
These yarns are finer, resulting in lighter fabrics and opening up new
possibilities in product design.
Earlier, most woollen and other animal fibre fabrics were produced either
on projectile weaving machines or on rigid/ flexible rapier weaving machines.
Air-jet weaving machines are not suitable for production of heavyweight
woollen fabrics, but are increasingly being used for making lightweight
worsted products. Air-jet weaving technology is a good choice for weaving
long runs with little variation. In all other cases rapier technology is advisable.
Water-jet weaving machines cannot be used to produce fabrics of wool and
similar animal fibres.
In the early 1990s, only Japan’s Tsudakoma Corp. and Toyoda Automatic
Loom Works Ltd manufactured air-jet weaving machines for making worsted
fabrics. With the introduction of new generation, more flexible air-jet machines,
the choice has widened. Sulzer continues to be the leading manufacturer of
projectile machines that were widely used to produce fabrics of wool and
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similar animal fibres. Flexible rapier weaving machines are available from a
small number of Italian and Belgian companies, while rigid rapier weaving
machines are available through several European woollen fabric makers.
5.4.2
Rapier machines (rigid and flexible)
All modern rapier weaving machines are modular in design so that each
machine is based on a common platform designed to accommodate future
extensions or conversions. This modularity safeguards the mill’s investment:
no other weaving machine is so easy to adapt in order to take advantage of
new market opportunities. Designed for universal use, a very wide range of
fabrics, from 20 to 850 g/m
2
 can be woven on these machines for uses
ranging from household textiles to industrial goods. One unique advantage
of rapier machines is the minimal stress on the filling yarns. Up to 16 different
filling yarns, with yarn counts ranging from 5 to 1000 tex can be inserted at
rates of 1400 m/min. Many other features have been added recently.
Shed geometry has been an area of attention. The short stroke of the sley
and the frames and the redesigned rapier heads allow the machine to weave
with smaller shed opening. Less stress is thereby put on the warp ends,
resulting in increased warp friendliness. The optimised shed geometry leads
to uniform fabric characteristics over the whole width. The location of the
sley cams is below the fabric and this allows heavier beat-up forces, so that
fabrics with high cover factors can be woven with ease.
Rapier tape guiding is another area that has received recent attention.
Most machines now offer two interchangeable guiding systems for the rapier
tape. The ‘Guided Gripper’ system offers higher speed while the ‘Free Flight’
system provides higher versatility. The rapier tape in the Guided Gripper
system is guided by one-piece hooks. Industrial speeds are obtained through
use of a small shed and a small rapier head. In Free Flight systems, the rapier
tape is not guided by hooks, as the yarns can be damaged by hooks diving
into the warp yarns. Rather the rapier is guided by supporting hooks for wool
or worsted weaving.
Versatility is enhanced by a Quick Step filling presenter that is modular,
allowing a loom to start with a four-colour insertion and to then add more
channels depending on the need. The colour and weave pattern are controlled
by microprocessor or jacquard. Such Quick Step modules are interchangeable,
and there are no mechanical drives, so no maintenance or lubrication is
required.
The same basic thinking applies to setting of warp tension with the unique
Tension Sensor Feeler (TSF) device. A sensor incorporated in the ends of the
whip roll eliminates unwanted effects from friction and vibration. In a similar
way, the programmable filling tensioner (PFL) for the weft yarn can be
programmed to add prescribed amounts of tension to the weft at precisely
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chosen moments during the insertion. In this way, not only are the weakest
yarns treated gently, but also the weft tension in the fabric is under control.
Fine tuning of the insertion settings is made very easy and accurate with the
tension meter.
Ultimate quality is obtained with the knot extracting device, which makes
sure that every metre of fabric is monitored to remove knots in the weft yarn.
This fully automatic system detects and removes the knots in the weft yarn
before they enter the fabric, so ensuring the best quality.
Rapier looms for woollen and worsted weaving are offered by manufacturers
such as Dornier (HTV S), Somet (Super Excel), Picanol (Gamma 4R), Sulzer
(G6200/250/300) Vamatex (Leonardo) and others.
5.4.3
Air-jet machines
Most of the recent advances have been witnessed on the air-jet weaving
machines. These machines are emerging as the preferred alternative for high-
speed weaving with low power consumption, flexibility and versatility with
minimum maintenance and maximum profitability. Machinery designers have
focused on three basic criteria: higher performance, immediate fabric quality
and full modularity.
Speed or rates of filling insertions (RFI) of 2000 m/min on air-jet weaving
used to be the limit a few years ago. This limit has been overcome by a
number of manufacturers. The 2003 ITMA saw a number of manufacturers
offering fast, wide-width air jet machines. Lindauer Dornier’s air-jet machines
AWSL 4/EasyLeno was shown weaving leno fabric at a speed of 450 picks
per minute (ppm), or RFI of 2349 metres per minute (m/min). The machine
featured a new main nozzle and positive weft clamp that allows the machine
to hold the yarn prior to insertion. Dornier showed another air-jet weaving
machine with dobby machine in a 200 cm nominal width that weaves the
finest wool fabric with wool/elastane filling at 900 ppm. Picanol featured a
wide range of air-jet machines of which at least four exceeded 2000 m/min
RFI. By making the insertion cone shorter and more slender on its OMNIplus
800 loom, the load on the weft yarn was reduced, allowing higher speeds. At
the same time, an entirely new 16-hole relay nozzle has been developed
which, in combination with the short reaction time, enables the loom to
weave more fabric with less usage of air. Promatech showed three air-jet
machines, the fastest being the 3.4 m wide Mythos Tec, shown weaving at a
speed of 2496 m/min RFI. Sultex featured the 2.1 m wide L5400 machine
that wove a womenswear fabric at a speed of 2079 m/min RFI.
The higher speeds also demand that the frame and all moving parts are
perfectly balanced and robustly built. The new hybrid harnesses are made of
aluminium with carbon fibre reinforcements. Another innovation has been
the introduction of variable speed weaving. It becomes important when weaving
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different filling yarns of different qualities. A weaker yarn needs to be run at
low speed while stronger yarn can handle much higher speed. The variable
speed function makes it possible to program the speed pattern according to
the yarn quality, the number of harnesses and the pattern, so that a higher
overall speed can be maintained – the maximum speed is no longer determined
by the weakest yarn or the most complex part of the pattern.
Picanol was the first to introduce a powerful motor named Sumo. This
allows the machine to be driven directly without belt or clutch at different
speeds as desired. The speed of the motor is controlled electronically, without
a frequency converter, reducing power consumption and permitting greater
flexibility. The starting torque is very powerful and adjustable. The beat-up
force is constant from the start throughout the entire weaving process. Since
then, Dornier & Promatech have also showed variable speed weaving machines.
The highest difference in speed was shown by Dornier and Picanol to be 100
picks/min.
Along with variable speeds these machines also offer variable pick densities
that allow the weavers to produce fancy effects in the filling direction. The
variation in pick density has been achieved through modularity and by
controlling electronic let-off and take-up mechanisms via a microprocessor.
The difference between low and high pick density (pick density range) is of
the order of magnitude 11–200 picks/cm.
5.4.4
Jacquard shedding mechanism
With the high pace of innovation it is important that weaving machines offer
a modular basic platform designed to receive all future extensions and
adaptations, thereby safeguarding the investment in the machine. Modularity
also allows easy adaptation of new developments to take advantage of new
market opportunities. On most looms today the basic machine structure for
the cam, dobby and jacquard versions is identical, making it possible to
change the shed formation system at some time in the future. It is possible
to change from cam to dobby or jacquard, and vice versa. The superstructure
mountings are also identical, making it possible to decide at some time in the
future to add features such as a fancy beam. On the latest versions, even the
controller area network (CAN) bus technology allows new features to be
added without complex extra wiring or printed circuit boards being required.
Recently jacquard weaving has been radically transformed by the
introduction of modularity and modern technology. With the introduction of
new jacquard shedding concepts by the two major jacquard manufacturers
Stäubli and Grosse, jacquard machines are free of all mechanical constraints.
In the new concept, the jacquard head is independent of the weaving machine
drive since it has its own drive without mechanical coupling to the weaving
machine. It sits much lower and vertically over the loom frame itself. The
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dimension of the head as well as that of the tie width is the same as the reed
width. This allows the control of individual warp ends through harness cords
set vertically and eliminates the need for magnets, hooks, pulleys, springs
and the gantry. In turn, this has resulted in a smaller machine size and hence
lower building and air-conditioning costs, elimination of mechanical parts
leading to reduced maintenance in terms of lubrication/oil/filter change etc.,
quick style changes, faster speeds, and more freedom to designers.
Stäubli’s Unival 100 electronic jacquard machine individually controls
each end of a jacquard harness using stepping motors or actuators. The need
for hooks, knives, magnets and pulleys is eliminated because each harness
cord or heddle is attached directly to the motor. The selection and lifting of
the harness is performed electronically and hence fabric design is achieved
in the same way as any current electronic jacquard system. Electronic control
allows unlimited possibilities for shed formation (symmetrical, asymmetrical,
shifted, venturi effect shed, etc.) and frees the choice of shed opening and
motion for each warp thread or groups of warp threads. This provides weavers
with new opportunities that were not previously available in jacquard shedding.
Further, the Unival is also modular in its construction where actuators are
assembled in groups of 16 forming a module. The modules are mounted on
aluminium rails enabling jacquard capacities in the range of 6144 to 20 480
warp threads. This modular concept allows the Unival to adapt to any loom
width and yarn density. Various configurations are possible for the same
number of hooks depending on the density, the width of the fabric and the
available overhead clearance.
In Grosse’s Unished, the shed formation has been achieved by leaf springs
that are moved by actuators. The leaf springs control the bottom shed as well
as the top shed (a positive jacquard shed type). Each leaf spring is connected
to a heddle that controls one warp end. The configuration of the jacquard
head and the individual control of each heddle (or warp end) allow the
heddles to be set vertically. The jacquard head is mounted directly on the
side frames of the weaving machine, thus making quick style change (QSC)
possible in jacquard weaving. It is also easy to exchange the entire jacquard
head, including the heddles.
Jakob Müller AG Frick of Switzerland has also introduced a harness-free
jacquard shedding concept for narrow fabrics on its MDL/C label machine.
The shedding concept is based on individual electronic selection of warp
yarns using special heddle wires. Again, there is no traditional jacquard
head, harness or comber board and no hooks, pulleys and returning springs.
Advances in weaving technology in conjunction with the new jacquard
concepts have not only resulted in RFI values higher than 2000 m/min but
also in high levels of versatility in terms of style change (QSC), variable
speed and pick density. This means that intricate jacquard fabrics can now be
woven at the same production speed as that of commodity fabrics.
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5.4.5
Quick style changes and other advances
Beside increasing speed, loom makers have continued to innovate in making
weaving more versatile. All major loom makers now offer the QSC system
mentioned earlier, which is essential for versatility and productivity. QSC is
an important advance for wool weaving as wool tends to be woven in short
runs, is an expensive fabric, and quality must be maintained throughout.
Grosse’s QSC for jacquard reduces the time for a style change from 90 to 10
minutes, enabling short runs. Dornier’s air-jet and rapier machines are equipped
with a patented pneumatic shaft lock (PSL) system that permits locking and
unlocking of shafts using a touch display, facilitating quick change of warps
and styles in less than 30 minutes. Dornier also offers on-the-fly pattern
change on their air-jet machines that allows change from, say, sheeting to
napery fabric without stop. Today, pattern changing (within the same fabric
style) has been completely withdrawn from the list of standard loom stoppages.
In addition to QSC, loom makers have continued to innovate by introducing
many unique features for minimising non-productive time. All major loom
makers, for example, offer automatic pick finding, fast frame connections,
quick fastenings for warp beam and cloth roll, rapid width reductions on
both left and right side and microprocessors for setting the shed and selvedge
crossing times to increase the amount of time available for producing fabric
at high speeds.
In fabric forming, control technologies today offer the possibility of
monitoring and setting of control points like warp tensioning, pick density
change, machine speed, shed closure setting, selvedge binding and even
compressed air-jet opening and closing. Other options include control of
scheduling and generation of reports. ‘WeaveMaster’ and ‘Loomdata’ from
Barco connect the looms by means of a standard Ethernet network and
utilise the standard transmission control protocol/Internet protocol (TCP/IP)
to set up a connection with a company’s enterprise resource planning (ERP)
system. If the looms are equipped with on-loom inspection devices, the
company can automatically download the weave schedules as well as upload
work-in-progress reports, efficiency and quality data on stops and defect
information. The WeaveMaster production monitoring system also allows
automatic export and viewing of reports in a website environment, thereby
allowing travelling managers to keep close control over the operations in
their plants anywhere in the world via the company’s website. They have
access to any of the WeaveMaster reports used within the office. Weave
supervisors/production managers using personal digital assistants (PDAs)
with wireless capability can monitor their looms remotely. In case of a loom
stoppage for example, the supervisor can select the one that has stopped,
check the conditions for stoppage/defect, can override the error and turned
off the machine error light. This allows the operator to restart the machine.
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In other cases, the supervisor can make a decision on the difficulty of the
stoppage condition and have the proper people notified. The on-loom inspection
systems use either cameras or scanners to scan the entire fabric. The system
can now be installed between the front fabric rest and take-up rolls. While
this is an improvement over off-loom cloth roll and post-weaving inspection,
more than 1 metre of fabric can pass before the system can detect it. The on-
loom inspection systems can identify defects, capture and store their images,
report and map defects and stop the weaving process. EVS (Elbit Vision
System) offers an on-loom inspection system termed Loomtex, while Barco
and Uster provide their own versions of on-loom inspection, Cylopes and
Fabricscan.
Barco’s automatic on-loom inspection system, which detects warp and
filling defects, has the ability to generate defect maps and various quality
reports when connected to Barco’s QualiMaster. The defect maps contain the
quality of the fabric rolls in terms of defect types, along with the location of
those defects within the roll. The system has the ability to generate an XML
document on a secure website. The customers can download these XML
files and utilise them directly to optimise their cutting systems. Promatch
offers another type of inspection system, with a new electronic eye. ITMA
has demonstrated the electronic eye on one of their Lenardo Silver FTS
Rapier machines. The distinguishing features of the system are its small
dimensions, low cost and integration with the machine. The function of the
electronic eye is not only to detect defects but also to interact with the
machine and change the setting. While this may be true for some defects,
other defects would not be repaired or avoided without operator intervention.