Multiphase Weaving Machine:
Weaving machines are classified into two groups: single-phase and multiphase. In a single-phase loom, a single insertion of weft yarn is made in one revolution of the loom, the shed is fully opened across the whole width of warp, and the pick is inserted. In a multiphase loom, not just one but several sheds are formed, and at the same time several weft insertion elements enter the entire width of the warp.
Single-phase shuttle-less looms such as rapier loom, projectile loom, air jet loom and water-jet loom are considered to be the second generation of weaving machines in which the primary mechanisms of weaving (i.e. shedding, picking and beat-up) take place in one loom cycle, thereby inserting one pick in a single phase. Only one shed is formed across the width of the warp.
In multiphase weaving, several sheds are formed across the width of warp at the same time (Figure 2). Multiphase looms are considered to be the third generation of weaving machines. One of the latest multiphase looms can produce 1.5 yards of fabric in one minute.
In multiphase weft insertion systems, several weft threads are inserted at the same time. In the wave-shed weaving machine, the sheds are oriented wave-like across the whole warp width. In each wave, a small weft cop is drawn off as with the shuttle loom. Production machines have already been sold by various European loom manufacturers. However, this principle has not succeeded because of a lack of quality and flexibility. An automated system to fix weft breaks is another challenge.
Sequential multiphase looms provide sequential sheds in the warp direction, each for one weft insertion. This principle has been known for a long time. At ITMA 1995, Sulzer-Ruti presented its sequential multiphase weaving loom M 8300. Despite the high production speed, it was no commercial success, the main reasons being the low flexibility regarding patterns and the difficulties when fixing a weft yarn break.
All the weaving techniques discussed thus far require that the shed be open all the way across the machine for the device carrying the filling yarns to pass through the shed. This imposes a limit on loom speed. The multiphase weaving machine overcomes this limitation by forming many different sheds at different places across the machine and forming these only as the weft yarn inserted. In this way, a number of weft yarns can be inserted, one behind the other. As a section of the shed opens, the weft passes, and the shed closes, opening again in the new pattern as the next weft yarn arrives. Speed is increased because of the number of yarns that can be inserted almost simultaneously one right after the other, but the actual speed of movement of the weft yarns is lower than in other types of machines. For this reason, weft yarns that are weaker can be used. Sultzer Ruti, the manufacturer of a multiphase machine, states that its loom will insert upto 5,400 meters of pick per minute.
The process transforms weaving into a continuous process rather than a cycle of shedding, picking, and beating up. Multiphase weaving machine continually inserts weft yarns from yarn carriers. Rotary beat-up devices press inserted yarn firmly against previously formed cloth. If the pattern changes, small groups of yarns are changed into a new shedding position after each new yarn carrier has passed.
The operation of multished weaving machines is based on a series of wave like motions across the weaving surface. In general, fabrics woven on these looms do not have a true 90º angle between warp and weft; the weft yarns are slightly slanted, or skewed. Multished weaving is limited to special types of fabrics, but it can be expected to gain acceptance in the years ahead.
As many as 16 to 20 weft carriers insert the pre cut weft in a continuous process Instead of the intermittent process of single-shed weaving. Beating up and shedding arrangements are different. In this continuous weaving process, the number of picks per minute is doubled. However, multiphase looms have never been extensively used in the industry.
Principle of Weft Insertion in Multiphase Weaving:
Multiphase weaving can be achieved by employing two different principles, either: (a) in which shedding, picking and beat-up occur across the width of the warp, i.e. in the weft direction, or (b) in which these actions take place along the length of the warp (in the warp direction).
Several weft carriers, one behind the other, traverse the reed space and insert one pick length of weft yarn (stored inside them) at a time. Weft yarn is continuously drawn from weft packages and wound onto the weft carriers one pick length at a time. Their phase number and velocity determine the weft insertion rates. The shed and reed clearance open and close around each carrier as it traverses the reed space, the movement of the upper extremities of the shedding elements giving the impression of a wave motion travelling from picking to receiving side. The special reed motion impels the weft carrier through the shed, each of which inserts weft length as it goes. At their reversal point, the mobile reed dents beat the weft yarn emerging from the weft carriers against the fell of the cloth. Upon reaching the receiving end, the carriers then return under the fabric to the picking side for recharging, the weft from the package is transferred to the carriers and the process continues.
References:
- Woven Textiles: Principles, Developments and Applications, Second Edition Edited by K. L. Gandhi
- Handbook of Weaving by Sabit Adanur
- Principles of Fabric Formation By Prabir Kumar Banerjee
- Textile Technology: An Introduction, Second Edition by Thomas Gries, Dieter Veit, and Burkhard Wulfhorst
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Founder & Editor of Textile Learner. He is a Textile Consultant, Blogger & Entrepreneur. He is working as a textile consultant in several local and international companies. He is also a contributor of Wikipedia.
