Himanshu Chaudhary and S.K. Saha
Department of Mechanical Engineering
Indian Institute of Technology Delhi
Haus Khas, New Delhi-110016, India
Tel: (011) 2659 1135/6320; Fax: 2658 2053
Handmade carpet industry needs upgradation in weaving technology to meet the demand of quality carpets and the rate of production. Present looms to weave the carpets are made of wood, which are susceptible to termite attacks. The use of wood also causes deforestation. Moreover, the high tension required in the warps is generated by pulling a rope. This requires about 40-45 minutes by 2-3 persons. The traditional practice of generating high tension is laborious and demands a change. In order to avoid the above difficulties, an improved metallic loom has been proposed elsewhere which made weaving easy but the cost of loom is high. In the improved loom, worm and worm-wheel, and ratchet-pawl are used to develop tension in the lower beam and to lock the upper beam, respectively. In this paper, finite element analysis of the metallic loom is carried out to determine the critical stresses and deflection in its components so that optimum sizes and shapes of the structural members can be selected.
Keywords: Carpet loom, Finite element method, and Structure.
Handloom weaving of carpets is different in many aspects from the handloom weaving of the fabric . Handloom weaving of fabric almost replaced by sophisticated power looms but not the same has happened to the carpet weaving because of its inherent knotting system and aesthetic values associated with it. The oriental carpet, as shown in Fig. 1, is generally woven on a warp fixed almost vertically in front of the weaver. Required length of warp threads wrapped over upper beam called warp beam that supported by a pair of columns, about 1.8 m high. Tuft of wool or silk inserted between the warp threads, knotted it in with weft and warp, as illustrated in Fig. 2. The process continues along the whole row. Then, the row is pressed using a tool called beater . Carpet knotting continues according to the carpet design. Traditionally, oriental carpets are woven on wooden looms (Fig. 1), which are becoming economically, environmentally and functionally non-viable due to the following reasons [2-3]:
�Life is limited (5-8 years) due to susceptibility to termites and frequent investments are required;
�Need rope arrangement to generate high tension in the warps, which is laborious; and
�Over the time the wooden beams bend causing non-uniform tension in the warps. Hence, the carpet quality is affected.
With wooden looms, carpet weaving for large width becomes difficult because greater effort is required to put the warp threads in high tension. Tensioning requires 2-3 persons who pull a rope to rotate the beams, as shown in Fig. 2. Since there is no mechanical advantage in pulling the rope, the tensioning job is very tedious, and requires about 30-40 minutes. Moreover, in addition to the low life and deforestation, they are prone to accidents due to the damages done by the termites. Existing wooden components have evolved over the years based on the weavers� experiences. There is no literature reporting any systematic design of such components except in by one of the authors of this paper . In order to overcome the problems of existing wooden looms, Saha et al.  designed and developed a metallic loom, as shown in Fig. 3, considering all aspects of carpet weaving. The lower beam fitted with a worm and worm-wheel for developing tension in the warp threads. A ratchet-pawl mechanism is used to lock the top (warp) beam. Main components of the metallic loom  are shown in Fig. 3, where the upper and lower beams, and two side supports contribute to the 90% of the loom weight and cost. In order to reduce the weight and cost, it is important to know the critical zones of the beams and columns so that their sizes and shapes can be modified. In this paper finite element analysis of this structure is performed to locate the critical zones, whereas a modified design is proposed in a separate communications .