8. WEAVING PREPARATION
Conversion process of yarn into fabric requires many intermediate operations, wherein yarn has to subject with varied amount of tensions. Therefore, the yarn, that has to be used for weaving, must have adequate strength to bear with these tensile forces, otherwise it will show poor performance during fabric manufacturing (Rao 1998, Gangopadhyay et al 1999). Direct warping is generally used for preparation of ground warp beam while use of sectional warping machine for pile warp preparation is preferred. Venkatpathi (1999) discussed that yarn quality in terms of strength alone is not adequate for production of good quality of fabrics. In addition to yarn strength, other factors which play a crucial role in deciding weaving efficiency are uniformity, frequency of imperfections, long faults, slubs, count variation, twist variation and hairiness. Venkatpathi (1999) further added that many defects like slack end, pulled warp, sticky ends, broken pattern, etc., predominantly originate in preparatory section.
9. EFFECT OF WEAVING PROCESS VARIABLES
Swani et al (1984) assessed performance properties of terry towels made out of the open-end yarn and the ring spun yarn and found that there was no significant difference in the water absorption rate of ring and OE fabrics although yarn wicking rate was greater in fabrics of OE yarn. Absorption rate increased with increase in pile density but was not affected by pile ratio. Swani et al (1984) further added that maximum absorption for OE fabrics was better than for ring fabrics at lower fabric density and for comparable fabric weight. Ring fabrics showed better dry and wet abrasion resistance than OE fabrics. The abrasion resistance of the fabrics was maximum for moderate pile density and high pile ratio. The wet abrasion resistance was significantly lower than dry abrasion resistance of the fabrics.
Mukhopadhyay et al (1996, 1998) conducted studies on to improve the functional properties of terry towel fabrics made out of bi-component yarn. They developed a bi-component yarn comprising of cotton and a water-soluble synthetic fibre. The water-soluble fibre exhibited good compatibility with cotton during spinning. After weaving, water-soluble component of yarn was dissolved. This process reduced the twist level and resulted in a higher space in each loop. The resulting towel exhibited improved water absorbency, higher abrasion resistance, softer and lighter weight than towels woven using conventional yarns. The process had no adverse effect on light fastness or wash fastness.
Gangopadhyay et al (1999) conducted study on to assess manufacturing techniques of terry towels employed in decentralized sector with a view to identify measures to enhance productivity and functional properties. They assessed machines, processes and work methods followed at each stage of manufacturing such as winding, weft preparation, warping, sizing, weaving and wet processing. The team suggested modification in machines and process to achieve desired performance in quality and productivity of terry fabrics.
Mansour et al (1997) worked on to develop an expert system for terry weave. Most important weaving parameters being identified by them were cut and uncut loops, pile density and pile height. Manipulation of these weaving parameters affected various physical and mechanical properties such as water absorbency, tensile strength, abrasion resistance, fabric weight, thickness, handle etc.
Tarafdar et al (2002) has conducted studies for measurement of moisture transport in terry fabrics. In their study, they concluded that:
� Surface water absorption increases with the increase in pile height.
� With the increase in pile density, wicking behaviour increases both in warp and weft,
but quantitatively warp way shown more wicking absorbency than weft way.
� With the increase in arial density of the fabrics, the wicking height increases.
� The wicking height also shows an increasing order with the increase in thickness of the