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Yarn Storage In Knitting Mills

Organization policies and computerization help to reduce identification problems and contamination, while speeding up delivery and maximizing storage space.

Helmut H.A. Hergeth, Ph.D. and Gary W. Smith, Ph.D.

Yarn Storage In Knitting Mills Organization policies and computerization help to reduce identification problems and contamination, while speeding up delivery and maximizing storage space.  Total quality and quick response are prime requirements for any knitting mill. The primary place for influencing conditions that lead to fast response times and high levels of quality is within companies, since that is where there is the most direct control over conditions and policies.One of the areas that can influence both quality and agility is the storage of raw materials. Garbage in, garbage out is a rule that can apply to any manufacturing endeavor, and this also applies to knitting. Consequently, great care should be given to selecting appropriate yarns and ensuring a consistency of yarn quality by working closely with the yarn manufacturer and/or practicing quality control on incoming and in-use yarns. After taking great care in this area, it then becomes very important not to compromise yarn quality during the time yarn is stored and used. Yarn storage must keep the yarn free of anything that lowers its quality, including yarn mixups and contamination.Today, it is usually necessary to invest a significant amount of time and money in fast and flexible equipment, streamlined production and effective distribution systems, so that a company can survive in a world that reacts quickly. Part of this effort needs to be a streamlined yarn-storage system that allows easy access to correct yarns when they are needed, in addition to providing for a fast tracking of the quantities and types of yarn in inventory, etc.Given the high production rates in knitting and the ability to change products rather quickly, it is evident that particular attention needs to be paid to auxiliary functions such as yarn storage. After all, the team of mechanics at a racetrack is just as critical to winning the race as the driver of the racecar. Investments in yarn storage should also include procedures, policies or low-cost pieces of equipment. The cost impact of such investment on the product is rather low, but the potential return on investment can be quite significant. Yarn Storage CriteriaWith the help of questionnaires, researchers at N.C. State Universitys College of Textiles, Raleigh, N.C., attempted to find out the importance of yarn storage in U.S. knitting mills. The focus of the survey was on companies with up to 150 employees (See Tables 1 and 2 below).It can be noted that approximately 70 percent of the companies have a specified person in charge of yarn storage, so there is a clearly defined area of responsibility. Furthermore, in ranking items in order of their importance, the majority of knitters considered yarn quality and its condition as being the most important items. These were followed by yarn identification and availability.Yarn handling, contamination, transport, logistics, packing and inventory policies were all considered to be less important (See Table 1).After establishing important criteria for yarn storage, the survey investigated specific methods and tools used in the yarn storage area. It was found that approximately 39 percent of the respondents used computer-integrated systems in the storage area. This implies that using computers allows for faster and more reliable sorting of yarns and access to specific yarn lots. It also enables the mill to use software tools to track and optimize inventory.As can be seen in Table 2, most companies segregate their yarns by yarn type, followed by color and origin.Within the analysis of different-sized companies, it was interesting to note that the larger companies (over 75 employees) ranked delivery date as highly as yarn type as a criterion. This may be an indication that first-in, first-out (FIFO) rules are relatively more important for large companies than for small companies. Yarn Storage ProblemsOne of the key questions in the survey asked about problems encountered in yarn storage (See Table 3). Clearly, the most important problem noted was available space. Following a variation of Murphys Law that any task will require the allowable time, it seems that any inventory will fill all available space.The problems that ranked second, third and fourth in importance were identification clarity, prolonged storage time and proper storage.The ranking was slightly different for companies using computer-integrated systems for yarn storage. Prolonged storage time was ranked highest, followed by space and then by general identification issues (e.g., lost labels, location identification, ID clarity, etc.). For companies not using computers for yarn storage, lack of space was clearly the dominant issue, followed by identification issues and prolonged storage time.When examining storage space relative to identification problems and storage environment (lighting, temperature and humidity), identification problems were profound for both groups. Users of computers thus seem to have more concerns regarding the actual storage facility. Lack of space ranks in third place. For non-users of computers, storage environment takes third place.These differences in priority may be an indication that the use of computers in yarn storage actually reduces some of the space needs, possibly because of better inventory control, which apparently curbs duplication of yarns and storage of redundant lots, etc. At the same time, it was expected that computerization would lead to better scheduling and coordination of yarn storage and production and, consequently, to much shorter storage times. The survey did not confirm this expectation. Computer users actually indicated more problems with prolonged storage times. Because the survey results do not allow a comparison of actual storage times, problem awareness may be a result of becoming aware of the true storage times. It may also be that the computers are not properly linked to production planning, so that minimizing the storage times is not possible.Quite a few companies mentioned storage environment problems, and specifically, temperature and humidity, which is to be expected. Only one of the respondents ranked problems with air conditioning, but there was no indication of the nature of the problem.Concerning some of the ways yarns are stored, it was surprising to learn that contamination of yarns is not a bigger problem for knitting companies. Apparently, 91 percent of the respondents store yarn on the floor. This increases the risk of contamination with chemicals, water, lint, fiber mixes, yarn mixups or dirt. The same is true for storing yarn near knitting machines, as was noted by 76 percent of the surveyed companies. This may be partially because of different climatic conditions in the warehouse and/or in the knitting plant.In terms of identifying yarns and avoiding yarn mixups, most companies rely on manual (or visual) identification by operators. Bar coding was used by only 36 percent of the companies.The results of the survey show that there appears to be an inverse relationship between prolonged storage times and the implementation and enforcement of FIFO policies. This, of course, follows the concept that enforcement of inventory rules tends to reduce inventory level, and that specific FIFO rules tend to reduce the average time that yarns are stored in inventory. Reducing Storage ProblemsThe survey showed that knitting companies are not using all of the technology and techniques available for their warehousing systems. For smaller and mid-sized companies, the degree of computerization in the yarn storage area is quite low. However, it becomes clear that some of the typical storage problems can be reduced without major investments in facilities or computers. These problems are especially related to identification and contamination issues. Organizational policies rather than equipment can help reduce these problems as well as lead times and associated average storage times. Thus, in order to streamline the overall operation, the integration of yarn storage and production planning is imperative. For smaller operations, this may be possible through organizational steps only, but larger operations may need to computerize their yarn storage to optimize benefits. The survey and its analysis also made apparent that seemingly minor issues can lead to great benefits without much cost. 

Table 1
Table 2 
Table 3Editor's Note: Helmut H.A. Hergeth, Ph.D., and Gary W. Smith, Ph.D., are both associate professors in Textile and Apparel Technology and Management at N.C. State University's College of Textiles.

September 2000