In the last two decades spectacular progress has bees made in the field of weaving technology and the most significant being the replacement of convectional looms by shuttleless looms for increasing productivity and quality of the end product.
Shuttleless weaving is making an impact on the textile industry. The change over from fly shuttle to shuttleless involves both new technology and shift from labour intensive to capital intensive, mode of production. Moreover, for export market, the quality requirements are becoming more and more stringent with the result that the export of the Indian mills is falling. Market demand is also for long lengths of fault free cloth, which is only possible with shuttleless weaving machines. Increased labour cost without any corresponding increase in productivity is resulting in reduced profit to mill owners. So today, we are in need of shuttleless machines which are weaving from the lightest to the heaviest of fabrics and diversified products using materials like spun, jute, wollen, worsted, metal wire, glass fire, mono and multifilament etc. with good quality.
We always said that
- Width and length of the piece should be within acceptable limits.
- Fabric construction such as EPI, PPI, Warp count, Weft count, blend percent should be within limits.
- Fabrics should be free from contamination of colour flaks, polypropylene, hair and jute or within specified limits per 100 linear meters.
- Tensile strength of the fabric should be as specified.
- Major defects such as floats, continuous missing end, wrong drawn-end, double end and double pick, visible to the eye should be absent.
To achieve above specification of fabric, the machine makers started developing their weaving machines. While modernizing they also touches the cost factor. For reducing manufacturing cost machine makers has given attention to energy and spare part consumption. So further we discuss about developments in weaving machines.
DEVELOPMENTS IN SHUTTLELESS MACHINES
When the topic of developments in shuttleless machines is discussed in any group/forum a question first arises is,
“Why Shuttleless Machines?”
In-fact the modernization or automation is not just for reducing man power. So is the case for installation of shuttleless machines. Our country lacked behind in global market competition mainly due to this aspect.
The benefits of installing shuttleless machines are as follows
- Better and assured quality fabrics produced.
- Higher rate of production.
- Consistency and reliable performance.
- Assured delivery time.
- Flexibility of the machine.
- Scope for manufacturing creative products.
- Better-engineered fabrics, wider fabrics etc.
To earn trust with customer and to form long term customer base manufacturing/facility should comply with above requirements. This justifies the need for going towards shuttlelessnization.
So in order to achieve good quality fabric the machine manufacturers develop their weaving machines by introducing various features.
Among the shuttleless machines considerable developments are observed in three basic picking principles i.e. projectile, Airjet and Rapier. While the new picking style i.e. multiphase weaving. We discuss one by one.
FEATURES COMMON IN ALL MACHINES: –
Several essential features found common with all shuttleless machines are listed below
- Higher speed
- Wider width.
- Electronic take-up and let-off.
- Shedding systems- cam , dobby and jacquard (mechanical and electronic).
- Electronic monitoring of weft yarn flight.
- Electronic warp stop motion.
- Automatic pick finding.
- Quick style change.
- Microprocessor controls with digital display.
- Low noise and vibration.
- Tension free weft supply by weft accumulators.
- Microprocessor control lubrication system.
DEVELOPMENTS IN PROJECTILE MACHINES
1) COLOUR SELECTION: –
- 1 X 1, 2, 4 and 6 colours can be used in weft direction.
- The system is freely programmable and operated by servo controller.
- No limitations on feeder position shifting.
2) ELECTRONIC WEFT BRAKER: –
- This device keeps a uniform tension on weft.
- The braking force and the braking duration are programmable.
- Program can be given for each pick.
- The device is driven by stepper motor.
3) Pre-acceleration to weft yarn is given by compressed air, which relieves extra tension in weft while inserting.
4) K3 Synthetic projectile can be used for weaving of delicate yarns.
5) The no. of heald shafts operable by cam motion is extended to 14.
6) Speed has been increased upto 1400 mpm (470 rpm). Due to improvement in many related mechanisms.
7) LED display at signal pole for machine speed, projectile arrival time, angle of machine stop, etc. which helps in monitoring of process.
8) Automatic weft brake repair motion enables shifting of feed package to a reserved one in the event of weft break between package and accumulator, no stopping of machine which increases the machine efficiency.
DEVLOPMENTS IN AIRJET WEAVING
The Airjet weaving machine continues to dominate as the machines of very high speeds. Today, practically (an Indian condition) at 1200 rpm the machine works or wider machine can attain a WIR of 2500 mpm. The system had the disadvantage of higher energy consumption due to the usage of compressed air in picking which accounts for 60% of total energy consumption.
The machine makers claim a reduction in energy by about 10% (Sulzer, Somet ) in their latest models. The developments in picking related systems have helped in expanding the horizon of weft material and count. The yarn colour selection upto 6 or 8 beyond which demand is very rare. That means, the major limitations of the system are being attended and scope for applicability has been increasing.
LATEST DEVELOPMENTS: –
- Modification In Weft Insertion System: –
The multi nozzles are divided into two zones and connected directly with separate tanks. The weft yarn requires higher pressure at later part of its flight, and this separation has helped greatly in optimization of pressure in duration of Jet opening.
o The weft insertion, based on a precise electronic control that includes ATC (automatic timing control), also uses newly developed nozzles, which guarantees optimum weft insertion conditions.
o Independent pressure tanks make it possible to set weft insertion pressures at optimal levels, this makes a significant contribution to energy conservation.
o All settings regarding picking is done by microprocessor keyboard, which reduces machine down time.
- Tandem Nozzles: –
In tandem nozzles, the two main nozzles are arranged in series so called tandem nozzles.
a. It reduces the nozzle pressure
b. Saving in energy
c. Also use of wider weft count range.
d. Low pressure weft insertion to occur, making effective for super high-speed operation accommodating yarns with low breaking strength.
- Tapered Sub-Nozzles: –
It consists of a tapered hole to prevent air dispersion.
a. It enables stable weft insertion with lower air volumes.
b. It stabilizes air injection angles during weft insertion.
c. The weft insertion is more stable and requires less air.
v v Tapered Tunnel Reed: –
A tapered shape has also been applied to the tunnel selection of reed blade.
1. 1. It helps in preventing air dispersion.
2. 2. The weft insertion is more stable and requires less air.
- Electronic Braking System: –
One of the serious drawback of Airjet picking was tension peak in weft when brake is applied. The electronic braking system can precisely control braking time and brake stroke, which significantly reduces tension pick, thereby reduction in weft breaks.
- Automatic Pick Controller: –
For smoother working, all machines have weft arrival time sensing and correction of pressure at nozzles but when package is changed from empty to full package, the arrival time will be delayed and this would be beyond the capacity of such a correction system. With APC (Automatic pick controller), this problem is attended.
- It instantly corrects the main nozzle’s air pressure for timing control during full cheese changes.
- It adjusts automatically nozzle air jet pressure, which compensates for variations in the travel timing of weft yarn.
OTHER DEVELOPMENTS: –
- Weft feeder threading is comparatively time consuming and, now the self-threading by pneumatic system is done.
- The weft cutter is electronically controlled and operated by steeper motor By this, cutter can easily adapt to any cutting time to the accuracy of 1°. Style changing time is saved.
- With the help of mechanopneumatic tucking device can hold the weft at both selvedges firmly during beating and then tuck-in. this eliminates auxiliary selvedge and weft waste is zero. The system can work upto 850 rpm.
- Almost every machine manufacturer supplies positive easing motion for maintaining constant tension during shedding and beating.
- There is a new shedding concept introduced, in which the heald shaft is directly controlled by Servo Motor. Thus the total motion of heald shaft can be independently programmed.
DEVELOPMENTS IN RAPIER WEAVING: –
The Rapier machines are emerging as weaving machines of the future. They are not far off from Airjet in production (Speed ) rate (upto 1500mpm or 600 to 800 rpm) without scarifying their special status of flexibility. They have been making inroads to heavy fabrics (900 gsm) and also shedding off the known drawback of higher weft waste.
SPECIAL DEVELOPMENTS: –
The design improvement in Rapier gripper permits handling wide range of yarns without any need for changes.
The machine owes its speed, flexibility and low energy consumption to a combination of high technology and economic design. Style changes can be executed ‘Exceptionally rapidly’. having independent motor drives, this yielded fewer moving parts, fewer gears, fewer oil seals and no timing belts i.e. there are fewer elements to influence fabric quality, less need for resetting and reduce maintenance. There are no toothed belts, which are prone to wear, and breakage.
- Saving on energy consumption of more than 10% in comparison with conventional clutch and brake configuration.
- Machine speed setting is done accurately and completely, electronically via the keyboard of microprocessor. This reduces the setting time to zero.
- Speed setting is easy to copy to other machine either with electronic set card or with production computer with bi-directional communication.
- Automatic pick finding becomes faster, which significantly reduces the down times for repairing filling and warp breakages.
- The machine can always work at optimum weaving speed in function of quality of the yarn, the number of frames, and fabric construction.
PFL (Program mable Filling Lamellae): –
It controls the filling brake ensures a current yarn tensions at any time during insertion cycle. The PFL can be installed for each channel between the pre-winder and entry of fixed main nozzle. It has been designed to slow down the filling at the end of insertion. The PFL thus significantly reduces the peak tension of the pick at the end of the insertion and decrease the tendency of pick to bounce back in the shed. As a result of which the filling tip is stretched correctly.
- Lower peak tension in filling yarn.
- Reduced tendency of filling to bounce back.
- Inserted pick can be stretched more easily.
- Adjustments are done by means of machine keyboard and display.
- The settings can be adopted for each filling yarn.
- Fewer filling breaks.
- Fewer machine stops.
- Better fabric quality.
- Higher productivity of machine and staff.
- Weaker filling yarn can be used.
- Correct setting of filling waste length and consequently less waste.
QSC (Quick Style Change): –
With quick style change just one person can carry out a style change in less than 30min. This is achieved by swapping the whole back part of split frame, with the warp beam, the back rest and the supports, the warp stop motion the harness and the reed.
Additionally this unique system makes it possible to carry out all article related settings on the warp side outside the weaving shed, before the style change, QSC not only reduce labour requirement but also result in efficient planning of warp and style changes. The key to the operation is the split frame design, several extra modules and warpy modules transporter are also required.
- Reduce machine down time.
- Interference losses due to simultaneous stops are practically non-existent.
- Fewer personal required for warp and article changes in weave room.
- Warp changes can be replaced by style changes, enabling the load on the tying and drawing-in equipment to be balanced instead of having two bottlenecks.
QUICK STEP FILLING PRESENTER: –
The filling can be presented at low tension, which avoids unnecessary filling breakages. The quick step-filling presenter operates with independent modules. Each consists of electronically controlled stepper motor with presenter needle and the system handles upto 8 colours. The weaver can enter colour pattern through microprocessor keyboard or at jacquard control unit.
- It is monitored by weaving machine microprocessor so timing for presenting for filling yarn is perfectly synchronized with machine speed and weave pattern.
- The course of filling yarn is low and remains constant.
- The filling presenter also provides ideal position for re threading.
- The modules of quickstep are interchangeable.
ELSY (False Selvedge Device):
The unique ELSY full leno false selvedge motion is electronically driven by individual stepper motor. They are mounted in front of harness so all harness remain available for fabric pattern.
This only Rapier machine that allows selvedge crossing to be programmed on microprocessor independently of shed crossing even while machine is in operation. So result of resetting can be checked immediately.
The easiest position of rethreading can be set by a simple push button. When machine starts, the selvedge system automatically comes to original position.
PSO (Prewinder Switch Off): –
PSO is the system by which the machine does not stop immediately after a bobbin breakage, but continues to weave, until the weaver is available to repair breakage. The weaver is informed by flashing orange light that the machine carries PSO action. Consequently the waiting period for intervation of weaver reduced to zero, weaver can decide himself when breakage must be repaired, for this Piezo-Electric filling detector is used.
ELECTRONIC TAKE-UP AND LET-OFF MOTION: –
It plays important role. Required pick density can be programmed on microprocessor keyboard. No pick wheel required. The accuracy of settings make it easy to adjust pick density of fabric with optimum fabric weight and minimum yarn consumptions. By ETU make it possible to weave fabric having various pick densities.
The electronic link between let-off and take-up is an additional tool to manage the fabric marks. Warp beam driven by electric let off motion through separate drive wheel that stays on loom, ensures trouble free operation of let-off system and improve fabric quality.
FDEI (Filling Detection At The End Of Insertion): –
When weaving ‘lively’ yarns, use FDEI system. It checks the presence of filling at the end of insertion. The system detects short picks, rebounding fillings and prevent faults in fabric at right end.
At filling breaks, the machine stops and only the harness are moved automatically to free the broken pick for removal of weaver. The is outstanding since automatic pick finder is not driven by separate motor but monitored by hydraulic system. In this way a two speed slow motion become a standard luxury to the weaver. The transfer position of filling yarn in center of fabric is always correct even after changing the cloth for new style.
MULTIPHASE WEAVING MACHINE: –
The Sulzer Ruti M8300 Multiphase weaving machine has introduced a new concept to the principle of multiphase weaving. The phase wise shed formation is along the warp direction instead of weft direction and 4 weft yarns are inserted simultaneously.
- Shed Formation: –
The warp yarns pass over rotating weaving rotor and shed forming elements select and lift warp yarn for shed formation. The curve shape of the elements, rotation of rotor and movement of warp positioners help in selection and formation of shed by controlling the motion of warp positioner. The weave selection is made possible.
Weft insertion: –
The channel in the shed forming elements guide in insertion of weft. The weft is inserted by nozzles are similar to Airjet weaving. Additional nozzles between shed forming elements further support the weft. Four wefts are inserted at a time. The weft measuring, clamping, cutting, sensing and controlling are similar to air jet machines.
- Beat-Up: –
The combs located behind shed forming element perform the function of conventional reed. The lower shed, which rises after insertion of weft, lift the weft out of channel over the entire weaving width. The beat-up comb then catches the weft and beats up.
The modular design concept adopted has helped to change warp beam within 20 min. the warp beams upto 1600mm diameter can be used. The inclusion of batching motion for cloth winding has reduced change intervals.
Many machines are in operations since 1997- 98 and this might be the machine for mass production in future.
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