Most of the weavers today are aware of the factors influencing the breakage rate, although the relative importance contributing to these factors is not generally understood, opine PV Kadole, Manjunath Burji and MM Makandar.
The grey yarn as obtained from the spinning process has to undergo various processes such as winding, warping, sizing and weaving before it is converted into fabric. During its journey from winding to weaving, the yarn has to withstand various kinds of stress offered by different mechanisms. There are numerous factors which can affect the performance of yarn in weaving. The factors can be classified into following three classes:
- Yarn quality
- Condition of warp preparatory
- Loom action and conditions
This paper implies breakage only related to loom action and conditions. It is stated that the fibres are loosened out of the yarn structure by the abrading action of loom parts and ring around one or more yarns. So often a short length of fabric is woven, the weaving become totally impossible.
Other condition being equal the intensity of destructive action in the form of friction on back rest, in the heald eye, dropper and reed dents, depends on the magnitude of the reciprocating movement of the warp and repeats of the movement. The magnitude of movement is directly proportional to the width of the beat up strip. On other hand, the number of actions on each warp element is proportional to the fabric pack density being processed. The other factors contributing to the intensity of destructive action are: beat up force, coefficient of friction of the different elements and the extent to which the tension in the warp sheet varies and frequency of the action. The variation in warp tension and cyclic deformation arises largely from the beat up and shedding process.
In the process of weaving, the warp yarn is subjected to complex mechanical action. Some of these actions, location cause are listed in table 1. The end breakage rate for weavable single yarns depends upon irregularity of the yarn. Investigation of the causes of warp breaks in the weaving of spun yarns has shown that a substantial proportion of the breaks are caused by abnormal tensions sporadically occurring in individual threads as a result of obstruction of some kind.
In the traditional approaches to the problem of assessing warp yarn performance on the loom, researchers have investigated tensile strength of sized yarn and attempted to correlate it with weavability. However, the use of such tensile strength approach has not shown consistent correlations to weavability, because the process of weaving is far more complex and several authors have raised doubts as to this approach.
The failure of sized yarns on a loom is attributed to the cumulative damage caused by cyclic fatigue of relatively small forces combined with abrasion. The failure of warp yarns on a loom is caused by repeated cyclic elongation at small stresses well below the breaking point applied under static load. The phenomenon commonly known as fatigue is caused by the gradually diminishing resistance of the material, attributable to cumulative damage. Breakages on rapier weaving machine can be classified in to two categories – weft breakages and warp breakages.
Weft breakages on shuttleless weaving machines are seen due to thin places present in the yarn and due to elements of weft insertion systems like accumulator, tensioner, finger box and rapiers. Weft breakages are measured at loom cycle degree of 3600.
1.1) Breakage at 0 degree
- Weft thread breaks in accumulator
- Due to improper working of drum DC motor
- Drum disc/ brush damage worn out tensioner
- Finger height is not proper due to which weft not engaged with rapier causes weft break
- Early cutter timing of weft cutter
- L.H side fall selvage drawing denting not OK
- L.H side rapier pressure plate broken
1.2) Breakage in between 0 to 180 degree
Mainly in this zone weft breakage causes due to L.H rapier
- L .H rapier pressure plate not having proper pressure in that
- Cushion and kit leaver condition is not good
- L.H rapier wing damaged or making sharp edges at weft gripping area
- L.H rapier ribbon damaged or worn out causes vibrations in rapier and weft breaks occur
- If L.H rapier opener setting is not proper
1.3) Breakage in between 180 to 310 degree
Mainly in this zone weft breakage causes due to R.H rapier
- If R.H rapier pressure plate not having proper pressure
- R.H rapier slider damaged or worn out
- Spring Paul condition not good
- R.H rapier hook damaged or bend
- R.H rapier ribbon damaged or worn out causes vibrations in rapier and weft breaks occur
- If R.H rapier opener setting is not proper
Warp breakages are mainly divided into four zones:
- W1 : R.H side warp break
- W2 : L. H side warp break
- W3 : R. H side leno break
- W4 : L.H side leno break
2.1) W3 and W4 breakages (leno breakages) Leno breaks are due to:
- In reed – due to damaged reed, damaged rapier, damaged rapier ribbon.
- In clocker – if alignment of clocker and ‘L’ plate is not proper or damaged clocker and its pin
- Alignment of leno device and leno bobbin stand is not proper causes leno breaks
- If leno bobbin thread tension is not proper
2.2) W1 and W2 breakages (warp breaks)
The warp breaks mainly depends upon warp condition, machine condition, settings and environmental conditions.
2.2.1: Warp breaks during weft insertion:
- Due to damaged reed and worn out sharp dents
- Rapier causes breaks during weft insertion
- If L.H rapier wing damaged, L.H rapier ribbon damaged or worn out, damaged kit leaver causes (W2) warp breaks
- If R.H rapiers hook, body, kit lever, R.H ribbon damaged causes (W1) warp breaks
- If rapier guide hook are damaged or worn out causes warp breaks as well as multiple breaks
2.2.2: Warp breaks in heald frame Warp breaks in heald frame due to
- If heald frame height is not proper or well staggering is not down
- If according to weave and combination shade angle is not set causes warp breaks in heald frame
- If heald frame side support damaged or insert damaged causes warp breaks
- If dobby lever bends, damaged or not working
- If condition of heald wire is not good
- Density of heald wire is more per heald frame
2.2.3: Warp breakage at back side Back side breakages are due to
- If warp stop motion setting not proper (tilt or bend)
- More tension on warp sheet
- Eccentric back rest roller or damaged roller and worn out back rest bearing
- More oscillating back rest due to incorrect position spring and its setting
- Worn out and damaged drop pins
- Sizing-related problem
Majority of breaks are mainly confined to the shedding zone (i.e., from fell to lease rods or drop wires). If proper care and maintenance of machine is done the number of breaks can be reduced for giving better productivity and good quality fabric. Breakages are measured in terms of breaks per centi-million picks.
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PV Kadole and Manjunath Burji are from the Department of Textiles, D.K.T.E’S Textile and Engineering Institute, Ichalkaranji – 416115, Maharashtra.MM Makandar is from Raymonds India Pvt Ltd Kagal, Maharashtra.