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

Automation
Adequate automation reduces idle times considerably, thereby rendering the
system more cost effective. The new modular structure allows a level of
automation to be attained to suit specific requirements. The mill can opt for
an automatic cutting device to reduce down-times, automatic carriage insertion
to save time and effort, or an automatic tying and cutting device for optimal
batch change.
Choice of thread tensioning device
There are several of these devices available on the market. Isotens devices
provide optimal and even tension control, suitable for the processing of all
yarn types, both filament and non-filament yarns, centrally operated and
regulated, with dustproof protection, and soft thread handling. For technical
yarns Dynatens-type tensioning devices allow perfect unwinding of technical
yarns without damaging the fibrils, they are centrally operated (moved and
adjusted) and feature long roller life. For yarns that need high unwinding
tensions Megatens-type tensioning devices are available.
Waxing devices
The waxing device is positioned between the warper and the beamer. As an
example, in the Versomat, provision is made for a waxing group that applies
waxes and special products before the beaming stage. The device is made up
of a grooved roller supported by the motorised waxing roller with a waxing
tank which can be lowered. This device is useful for dampening and lubricating
the threads and, above all, for binding the lateral fibrils of the yarns with
special additives so as to ensure optimal weaving on the loom. For single
wool worsted yarns, a size bath is used at warping to apply either hot or cold
size.
5.3.3
Drawing-in, tying-in and dropper pinning
In modern drawing-in machines the process of taking the warp ends from a
warp sheet and drawing-in into healds, drop wires and reed is fully automated.
Drawing-in is done using robot-like machines on a special type of heddle.
Heddles are separated from the stack and brought to the drawing-in position.
A plastic knife opens a gap in the reed, and a hook draws-in the warp end
through the heddle and reed in one step. A drawing rate of 50 000 warp ends
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per 8 hours (200 ends per minute) on these machines provides independence
from availability of trained staff, consistent quality of drawing-in and perfect
draw-in independent of drawing-in pattern, number of frames and type of
yarn.
Stäubli is a leading manufacturer of these machines. The Delta series of
drawing-in machine, which was launched on to the market in 1991, continues
to have the highest degree of application flexibility and drawing-in capacity.
Delta works without any restrictions on the harnesses which could be drawn
in, that is to say the healds, drop wires, reeds and frames. No separating aids
such as angled parts or keyholes are now required for separating the healds
and drop wires from the feed stacks. The user is not forced to renew the
harness park in the event of buying a drawing-in machine. The new Opal
automatic leasing machine by Stäubli can combine several warp sheets (from
one to eight sheets) of multi-colours or single colour into one lease to prepare
such a warp for automatic drawing-in or tying-in. The machine is equipped
with a camera system to ensure the correct yarn colour order as programmed
by preventing doubles and distinguishing between threads of different colours.
Depending on the application, the leasing speed of the Opal is up to 100 000
threads per 8 hour shift. Some Japanese manufacturers are offering an air-jet
automatic drawing-in machine, which uses compressed air instead of needle
hooks or grippers to draw in the warp yarns through the harness (droppers,
healds and the reed), giving improved fabric quality by eliminating damage
to the harness.
On a loom equipped with quick style change, the Delta product range is
supplemented by Warplink equipment in order to rationalise and automate
the processes between warp beam storage and the weaving room. The drawing-
in process is followed by the process of welding a piece of plastic foil to the
warp using the Warplink. Thanks to Warplink there is no longer any need for
tying the warp ends to the tying cloth when laying the warp into the weaving
machine. This is normally a time-consuming operation, which has to be
carried out by specialists. In contrast, the laying of the plastic foil into the
drawing-off rollers takes only a couple of minutes. Another advantage is that
the plastic foil guarantees an even yarn tension over the whole width of the
warp, making weaving start-up much simpler and less time-consuming. In
this way, time savings of between half an hour and an hour can be achieved
at each article change.
Tying-in
A small portable robot is used on or off the weaving machine for tying-in. A
typical warp-tying machine can knot single or ply yarns of varying fineness
and content at a usual rate of 60 to 600 knots per minute. The number of
warp ends to be tied together can be preprogrammed; once this number is
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reached, the knotter stops automatically. A dual knotting system is used on
a double-beam weaving machine. The knotters work from left to right and
from right to left simultaneously. In recent years, knotting machines have
been improved not only in mechanical reliability but also in ergonomic
aspects. All machines now provide the four essential knotting alternatives,
lease-to-lease, sheet-to-sheet, sheet to lease and lease to sheet. In recent
years the free length of yarn between the clams has been extended by some
40% in some machines so that the same extensions in knot formation can
reduce the strain and stress by the same percentage. The machine is highly
flexible with a capability to tie single and double knots, to tie yarns in a
count range from 0.8 to 500 tex and the reference thread tension is recorded
independently and continuously for each individual warp sheet.
Dropper-pinning
The use of the open type of drop wire has increased steadily in recent years
and it is estimated that 50–60% of all drop wires in current use on weaving
machines and looms are of this type. Closed drop wires must be drawn
automatically, semi-automatically or by hand, but open-ended drop wires
can be either drawn or pinned. The pinning operation is normally carried out
in the loom on drawn warps, as knotted warps will already be drawn through
the existing drop wires. Some mills with a wide variety of heald frames and
different types and lengths of heald would find it extremely difficult to
effectively integrate a fully automatic drawing installation. Under these
conditions semi-automatic drawing, automatic entering of the reed and dropper
pinning of open-ended drop wires, either in a frame or the loom, provide an
economical alternative. Fischer-Poege is making dropper-pinning machines
that allow dropper pinning away from the loom.
5.3.4
Transportation and loading
The multi-width weaving machines have greatly increased the complexity of
the materials handling problem. Two 190 cm beams, frequently 10 or more
frames, six banks of drop wires and bars and commonly two or three reeds
are a handling package requiring special equipment. There are significant
problems associated with handling a two tonne, inconvenient and vulnerable
two-part load. The yarn must not be damaged or subjected to tension during
transportation from the preparatory department to the weaving machine or in
the transfer operation from truck to weaving machine. Appreciating the nature
of the problem and the desirability to minimise its frequency and associated
lost machine time, beam flanges have been steadily increased by loom designers
up to 1000 mm, but this further complicates the problem for the preparation
department. An electro-hydraulic loading device is essential to transfer a
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heavy set of frames, drop wires and reeds into the correct location for making
the appropriate connection of the machine. The time for complete transfer of
a multi-width heavy dobby set using the electro-hydraulic loading device is
about 20–25 minutes.