International Journal of Engineering Trends and Technology (IJETT) – Volume 30 Number 8 - December 2015 ISSN: 2231-5381 http://www.ijettjournal.org Page 393 Warp tension analysis of narrow fabric weaving and designing of tension compensator to avoid start up marks Dr.TSS Jayawardana #1 , GHD Wijesena #2 , Dr. EASK Fernando #3 , Prof. Rohana Kuruppu *4 # 1 ,3 Senior Lecturer, Dept. of Textile and Clothing Technology, University of Moratuwa, Sri Lanka # 2 Chief Technical Officer, Dept. of Textile and Clothing Technology, University of Moratuwa, Sri Lanka * 4 CEO, Brandix College of Clothing Technology, Ratmalana, Sri Lanka Abstract— Start up marks are one of the major defects on woven fabric and this defect occurs when loom restarts after stoppages due to warp tension variation at the time of start. This defect is more prominent in high speed looms and it is critical in manufacturing elastic tapes. In this paper, formation of start-up in elastic tape on a narrow fabric loom was analyzed mathematically and provided a practical technical solution to the problem. In mathematical analysis both continuous operational condition and stopping condition of a narrow fabric loom was taken into consideration and the developed mathematical model established a quantitative relationship between excess warp yarn length fed and the tension variation of warp yarn at the point of starting the loom. A system simulation was carried out using the model developed and compared with the experimental results to show the accuracy of the model. A tension compensating device was proposed to avoid formation of the startup marks. The effectiveness of the proposed solution was proven practically with a prototype developed. Keywords — lastic tapes, narrow fabric loom, tension analysis, warp tension compensation, start up marks. I. INTRODUCTION Apparel industrial sector acquired a rapid growth in the recent past to compete in the global market and this movement is mainly focused at achieving higher productivity with higher quality. In order to maintain high quality level in the end product, it is imperative to use good quality raw materials. As an essential part of the supply chain, raw material manufacturing for garment industry has been significantly developed and became one of the highest quality materials in the international market with no exception to the narrow elastic material. Still the full potential of productivity could not be met due to frequent fabric defects such as startup marks which are also known as irregular pick marks. Due to tension variations at stopping and starting of loom, pick density variation can be specifically observed in the elastic tape and it appears as a fabric flaw termed as start up mark. This defect is more prominent when the looms are operated at high speeds and it is crucial case in elastic fabric formation. Startup marks lead to create colour variations during dyeing process therefore it is essential to remove startup mark portion from the elastic tape before dyeing. The existing solution for this problem is to cut elastic tapes to remove the defective part and rejoin each tape with plastic tag pins which is not a value addition process and such practice concedes a large sum of money as well as experiencing an inevitable material wastage. Material wastage is significantly high in case of elastic bands with a design as the entire repeat having defects should be removed as a waste. Further, the efficiency of packing is reduced approximately by 50%, when a joint is detected by the layering machine as it is required to stop and operator has to cut the joint and connect two ends with an adhesive tape. Further operator has to match needle edge to needle edge, wire edge to wire edge and face side to face side in this process. Further elastic fabric manufacturing is done in large scale to cater for the very high demand and frequently occurring startup marks is a serious manufacturing problem which needs an immediate and sustainable solution. Depending on the nature, startup marks can be divided into two types namely open mark or thin start up mark and dense mark or thick startup mark. Open marks appear when there is decrease in pick density due to cloth fell go away from reed. At the instances of stoppage, warp tension decreases and open mark appears at the time of starting the loom. Dense marks appear when there is an increase in pick density and it occurs while the cloth fell moves towards reed. This phenomenon was described in the literature in the following manner. Thin start up mark appears as a result of lower warp tension while thick start –up marks are the result of higher warp tension, during restarting in comparison to steady state running tension [7]. The picks of synthetic yarn at cloth fell slip back when the reed moves back after beating up causing non-uniform pick spacing at the cloth fell. The backward movement of the picks at the cloth fell may occur due to both slipping and rolling back. Rolling back is easier than slipping back as it requires less energy. The release of energy stored in a twisted yarn promotes rolling back of inserted weft [9].