ABSTRACT

Revolutionary developments in cotton textile processing are quite evident in areas such as automation, electronic monitoring, and innovative machinery design. Despite these developments, quality problems which were witnessed over 50 years ago still represent unsolved mysteries in today's technology. These problems include:

1. Fiber variability. The variability in fiber characteristics is often conveyed to the yarn and fibers are not utilized to their ultimate potentials in improving yarn characteristics. For example, fiber strength is not fully translated into yarn strength and the deficiency of this translation may be as high as 50%.

2. Today's yarn can not be woven as spun because of the lack of a good surface integrity (i.e. acceptable levels of hairiness and abrasion resistance) which allows the yarn to withstand weaving stresses. Accordingly, the costly sizing operation has to be used just to make the yarn weavable.

3. Other problems such as yarn irregularity, imperfections, and high variability in yarn strength, although have been reduced, are still in existence and at much higher cost than in the past.

4. Attribute parameters such as endsdown in spinning or warp breakage in weaving still exist and at a much higher cost than in older machinery. This is due to the significant loss in efficiency when a breakage occurs even in a fully automatic machine. In a recent survey by the present authors, it was found that the average loss per a single endsdown in a fully automated open-end spinning machine can range from 14 to 54. The corresponding range in a fully automatic ring-spinning machine is from 24 to 74. In weaving, a single warp break may cost from 104 to $2.5 depending on the loom speed and the impact of the breakage on fabric quality.

5. New quality constraints and changes in the order of importance of fiber properties have been introduced as a result of using different spinning techniques. For instance, while fiber length and uniformity still holds a top position in both ring and air-jet spinning techniques, fiber fineness and strength are top priorities in open-end rotor spinning.

6. New terms of yarn quality parameters have been added to the familiar list of yarn characteristics. For example, in air-jet spun yarn, a problem which has been quite disturbing is the extent of "pull-apart". This parameter describes the length over which a weak zone of an air-jet yarn may extend. A minimum of about 2 inches and a maximum of about 2000 yards may represent a length of a "pull apart" zone. In these zones, yarn tends to easily break by slippage rather than fiber breakage creating problems during warping. It is believed that "Pull apart" is a quality problem resulting from the absence of effective wrapping of the core fibers by those on the surface. Ineffective wrapping could result from insufficient air pressure in the air nozzle due to clogging of nozzle holes by fine trash particles.

In recent years, there has been a significant change in quality implementation through the application of quality engineering in several industries both in Japan and the U.S. Quality engineering utilizes parameter design and tolerance design to reduce product development cost. In this paper, an overview of the concepts and theories of quality engineering in relation to cotton textile processing is presented.