Warp Breaks || Factors || Analysis

Warp Breaks:

The performance of the loom depends upon the rate stoppages due to warp, weft breakages and other auxiliary stoppages which occur due to mechanical reasons during weaving in the loom shed department.

Out of all these stoppages the time involved in mending is comparatively higher and thus, all attempts are made to reduce the warp breakages. A higher warp brake rate affects the productivity of the loom, increases the work load of the weaver and also affects the quality of the fabric.

During weaving, there are different forces which act on the warp which results in breakages. Some of the major forces are Abrasions, Extensions and Bending. The effect of abrasion of warp during weaving is the primary reason for the breakage. This is because this type of warp breaks happens into the shedding region, occurring in the healds or in the front shed since the abrasion action of the loom is more in heald to fell region as a result of the action of heald and the reed.

WHY A WARP BREAKS?

• During weaving, each element of the yarn is subjected to different destructive actions such as extensions, abrasion and bending due to which the yarn is weakened and fatigued.
• The tensile deformation accelerates yarn failure due to abrasion while the abrading action accelerates yarn failure as a result of tensile deformation and the intensity of the destruction depends upon the magnitude of the deformation.
• A sized yarn is basically composed of two elements, the yarn and the size film and these two elements react differently on a particular given action.
• The rubbing action will affect the size film first and repeated action of extension will destroy both the elements ultimately.
• The abrasion decreases the yarn strength due the rubbing action which develops the stress on the yarn and the size film. Thus, it can be noted that abrasion is the principle reason for warp breaks as it decreases yarn strength.
• The decrease in yarn strength increases elongation, as soon as the elongation exceeds the endurance limit it destroys the yarn structure and leads to breakages. Other reasons for warp breaks can be due to knots, breaks due to impurities, chopped ends, taped ends, twisted yarn, soft yarn etc.

FACTORS AFFECTING WARP BREAKS:

Quality of yarn: Yarn quality is the primary source that influences end breakage. This is because if the strength rate reaches below a stipulated level, the warp break rate increases rapidly. Therefore, a fuzzy, weak and non- uniform will break very often. That is why the quality of the yarn matters the most. The yarn required should be uniform, smooth, and strong so that it can withstand the stresses during weaving.

Quality of Yarn preparation: The end breaks during weaving are increased by preparatory deficiencies such as during warping, winding and sizing.

• Winding: The main objective of winding is to remove objectionable  yarn faults which if remain unnoticed will show up as fabric defects or will cause end breaks in subsequent processes.
• Warping: Warping should be carried out properly and the aim during warping should be minimizing the end breaks. This can be achieved by reducing warp tension.
• Sizing: During sizing, the size paste is coated in the yarn which helps the yarn during weaving process. This reduces the abrasion resistance and brings put the potential of the yarn. Proper sizing can ensure less end breakages. Some important aspects that should be looked after are machine efficiency, machine speed, selection of correct size paste and size pick up paste.
• During drawing: The heals and reed should be in proper condition, skilled operators are required, dressing of the loom should be properly done to avoid cross ends in the loom and should be a provision of extra- ends on the loom in case any end on the loom break.

Loom conditioning and setting: The mechanical parts of looms come directly in contact with warp and this influence the warp breakage rate in the following manner:

• Depth of shed and shed timing: More shed depth than necessary and early shedding leads to higher end breaks. There should be clearance of 2mm between top shed and top end line.
• Improper functioning of warp stop motion: The function of warp stop motion is to stop the loom as soon as the warp breaks. If the warp stop motion does not stop the warp breaks increases.
• Improper Loom cleaning: Fly and dust get collected on healds; drop wires, reed and fly should be cleaned from time to time.
• Atmospheric condition: The proper RH% should be maintained in the weaving department to ensure satisfactory loom performance. RH% is generally 75%-80% for 100% cotton yarn and temperature around 25-27 degrees and 65%-75% for blended yarn. These conditions are mandatory to maintain to prevent end breaks.

ANALYSIS OF WARP BREAKS

It is essential to analyze the causes of warp breaks so that proper remedies are incorporated.  The process of analyzing all types of warp breaks is a lengthy task and thus, warp breaks are classified into following heading

• Knots: As per the literature it is noted that 30-35% of warp breaks during weaving occur due to knots. This is because firstly, the knot may slip or break if it fails to pass through healds, reed etc. Secondly, due to the scissoring actions of knots, the adjacent warp threads are damaged. This type of warp break can be reduced by using spliced joints in the place of knots.
• Taped Ends: Two or more ends sticking together also causes warp breaks. This is mainly due to faulty working at sizing.
• Twisted ends: Here, two or more ends are twisted together compactly and tightly and effort is required to separate them. Such faults generally do not occur frequently.
• Breaks due to impurities: Fly which is sized and flattened produces warp breaks because of its inability to pass through reed dent, heald eye and drop wires. This type of break occurs in the shedding region and the back zone.
• Abrasion: The effect of abrasion of warp during weaving is the primary reason for    the breakage. This is because this type of warp breaks happens into the shedding region, occurring in the healds or in the front shed since the abrasion action of the loom is more in heald to fell region as a result of the action of heald and the reed.
• Unknown: Breaks for which there is no satisfactory proof as to their cause are recorded as unknown. According to the reports 33% of warp breaks are due to this cause.