What is Shuttle Weaving?
Shuttle weaving is a traditional method of weaving fabric. A shuttle in weaving is a device used with a loom by which weft is inserted on shuttle weaving machines. A shuttle loom uses a shuttle to carry the weft yarn. The shuttle carries a pirn (cop) on which sufficient weft yarn has been wound provide for the weaving of a few hundred picks. Each time the pirn runs out of weft, the shuttle has to be replaced with a fresh shuttle carrying a full pirn. The shuttle inserts the weft yarn in the shed during its traverse back and forth across the loom width. On both sides of the loom, picking mechanisms are fitted, which will propel the shuttle to the other end. The shuttle can be made out of wood or plastic. Figure 1 shows a shuttle used in conventional looms. A pirn is a small piece of tube made out of plastic or wood on which the weft yarn is wound. The size of the shuttle will vary according to the loom and normally it will be able to hold various pirns of different sizes. The size of a pirn will vary from 15cm to 25cm according to the requirement.
Conventional Loom:
In conventional looms as the weaving proceeds, the weft yarn is unwound from the pirn and inserted in the warp shed. Since the weft yarn package has a limited quantity of yarn, it will run out after a limited time. Usually after every 5 to 6 minutes, the loom has to be stopped, and the pirn has to be changed manually. Such weaving machines are used in small-scale enterprises (such as family workshops, small handicraft establishments, etc.) and older factories established for the development of specific types of fabrics. Figure 2 shows the schematic of a shuttle loom. Splitting the warp yarn into the top and bottom layers is called shedding. Propelling the shuttle into the warp shed with a speed is called picking. On each side of the loom, there is a picking stick which will hit the shuttle to fly to the other side of the loom. The shuttle will fly at a speed of approximately 15m/sec. On reaching the other side the shuttle will be stopped by shuttle checking system.
There are different mechanisms for shuttle picking. Figure 3 shows a cone-under-pick mechanism used in conventional looms. A cam is fixed in the cam shaft, which is continuously rotating. The cam hits the cone of the picking shaft, which turns and pulls the lug strap. The picking stick attached with the lug strap is also pulled, and it hits the shuttle through the picker, making the shuttle to fly to the other side of the loom. If it is assumed that the speed of the shuttle is 15m/sec and for a loom having a width of 150cm, the shuttle will take 0.1 sec to reach the other side.
The shuttle travels on the race board while the bottom layer of the warp yarn is between the shuttle and the race board. The reed guides the shuttle, and the race board supports the shuttle.
The reed and the race board are assembled on the two oscillating arms, which is called a sley. The sley oscillates back and forth by means of a crank mechanism attached with the main shaft of the loom as shown in Figure 4. During its forward movement, the sley pushes the inserted weft yarn to the fell of the cloth. This is called beat-up. The meeting point of the warp yarn and the newly formed cloth is called the fell of the cloth.
Timing Diagram of Shuttle Loom:
All the basic motions namely shedding, picking and beat-up are synchronized in a loom for its proper working. Taking the revolution of the crank-shaft as 360° and the beat-up position as 0° the start and end of all the motions are indicated in a circle. This is called a timing diagram of the loom. The timing diagram of a shuttle loom is demonstrated in the Figure 5. The timing diagram may be different for different looms. The beat-up position that is the furthermost position of the sley represents 0°. Picking starts 80° from the beat—up and lasts for 30°. The shed is fully open from 30° to 150°. Shuttle checking takes place from 260° to 290°.
Automatic Loom:
In a conventional loom, as soon as the weft yarn in the pirn exhausts, the loom has to be stopped, the exhausted pirn should be replaced with a full pirn manually and the loom needs to be started again. This will reduce the efficiency of the loom and involves manpower. A starting mark of one or two picks will be left in the fabric. To make the loom continuously run without stoppage for weft replacement, pirn changing mechanisms have been developed. Pirn-change mechanisms replace the exhausted pirn with a full pirn while the loom is running. The looms fitted with pirn-change mechanisms are called automatic looms. The automatic replacement of pirns and shuttles increases the productivity of weaving maсhines by between 25 and 200 per cent. Mechanisms for the automatic replacement of pirns and shuttles are used for change of weft of the same kind or colour (on single-shuttle weaving machines), or for the change of weft to a different kind or colour (as on multishuttle weaving machines). Figure 6 shows the working of a pirn-change mechanism.
Following the indication from the weft feeler for the exhaustion of weft, transfer latch 6 is lifted so that it positions itself against approaching bunter 7. As sley 8 moves forward, the bunter hits the transfer latch, which results in hammer 5 hitting the full pirn kept in battery 1 downwards, ejecting the empty pirn from the shuttle. The full pirn will position itself in the shuttle, and weaving continues without stoppage. All these things will happen in fraction of a second during the furthermost position of the sley.
Limitations of Shuttle Weaving:
Even though shuttle weaving is the most common and simple method of production of fabrics, for many centuries, it has its own limitations. The limitations of the shuttle weaving are:
- Shuttle weaving requires frequent replenishment of weft packages due to its smaller size, which increases the workload of the weaver.
- Because the shuttle has to be propelled back and forth, it requires a heavy mechanism, resulting in the consumption of spare parts.
- A separate pirn winding process is necessary to prepare the weft packages.
- A few layers of weft yarn are always left in the pirn after every full pirn used in the weaving. This needs to be cleaned before the pirn is used again for winding, resulting in wastage of weft yarn to a certain extent.
- The speed of the loom cannot be increased beyond a certain limit say 250 rpm due to the heavy moving parts of the loom and mass of the shuttle.
All the limitations listed above are mainly due to the method of weft insertion by the shuttle system.
Conclusion:
In shuttle weaving, whether conventional or automatic looms, plays a fundamental role in the production of woven fabrics. Conventional looms are slower and less efficient compared to automatic looms, but they remain valuable for smaller-scale or specialized fabric production. A manually controlled shuttle weaving machine has to be stopped in order to replace the shuttle. Shuttleless weaving machines provide higher weaving speeds, as the weft insertion on these machines is carried out using alternate weft insertion devices, which enables faster operation.
References:
- Fabric Manufacturing Technology: Weaving and Knitting by K. Thangamani and S. Sundaresan
- Mechanisms of Flat Weaving Technology By Valeriy V. Choogin, Palitha Bandara and Elena V. Chepelyuk
- Handbook of Weaving by Sabit Adanur
