http://ir.bdu.edu.et/handle/123456789/2132 Sat, 13 Jan 2001 07:37:26 GMT 2001-01-13T07:37:26Z http://ir.bdu.edu.et/handle/123456789/9300 AN INVESTIGATION ON THE EFFECT OF TOP ROLLER COT GRINDING AND ITS PRESSURE ON YARN QUALITY AND TECHNO ECONOMICS The critical part of ring spinning machine, at which yarn evenness and tensile strength can be greatly influenced is by the drafting arrangement. The main components in drafting have been subject to various studies in order to make a uniform even yarn. In this study an investigation was done on altering the front top roller cot diameter by grinding and adjusting top roller pressure. The study was undertaken in an industrial setup, 15 different combinations of rubber cot diameter and top roller pressure were tried to optimize the utility of rubber cots with enhanced cot service life without compromising the yarn quality to benefit Bahir Dar Textile Share Company, Ethiopia. The unevenness and tensile strength of 20s Ne 100% cotton yarn were investigated. The test results were subjected for statistical analysis and the worldwide quality standard of the results was also determined by USTER ® STATISTICS 2013 v1.1. The result showed that, the decrease in cot diameter by grinding critically influences the mass unevenness and imperfection of the yarns. It does not apparently influence the yarns tensile strength. Accordingly, cot diameters of 29.9mm and 29.6mm at pressure of 2.2bar and 29.3mm at pressure of 2.3bar was found as optimal pressure and cot diameter combinations which can be able to maintain consistency of yarn unevenness and extends the service life of the rubber cot. The techno economics of rubber cot usage was also investigated relating to cost economics at industry level and the result clearly indicates the benefit to the industry to use rubber cots for prolonged service life which can be able the industry to save about 129, 024ETB per a year per ring frame. Tue, 26 Mar 2019 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/9300 2019-03-26T00:00:00Z http://ir.bdu.edu.et/handle/123456789/9299 MANUFACTURE OF RECLAIMED FIBER NONWOVEN FOR SOUND ABSORPTION Recycling is the process of making or bringing out new products from a product that has originally served its purpose. The use of non woven’s for noise reduction is based on two major advantages of these materials, namely low production costs and small specific gravity. Through this thesis, an attempt was made and implemented an innovative technique of developing stitch bonded non-woven by using recycled fiber. Knitted wastes were collected from cut and sew knitwear factories and recycled by using fabric opening machine in Adey abeba textile factory. The opened fibers are carded by mechanical carding machine by varying the number of layers. Six nonwoven samples were manufactured by stitching the web structure with core spun yarn. The manufactured reclaimed fiber stitch bonded nonwoven sound absorption coefficients were measured according to ASTM E 1050 standard by an impedance tube. The results revealed that the sound absorption coefficient increased with increasing frequency level of 500Hz, 1000Hz, 1500Hz, 2000Hz, 2500Hz and 3000Hz. Factors influencing sound absorption of nonwoven materials such as fabric thickness, areal density, air permeability and thermal conductivity were tested. The results revealed that while thickness increases the sound absorbing performance also increases. Low frequency sound absorption has direct relationship with thickness. However, at higher frequencies thickness has insignificant effect on sound absorption. Less dense and more open structure absorbs sound of low frequencies. Denser structure performs better for frequencies above 2000 Hz. Air permeability of the stitch bonded nonwoven decreases the sound absorption performance increases. The mechanism of sound absorption was conversion of sound energy in to heat but the effect of thermal conductivity of stitch bonded nonwoven structure was very small. Tue, 26 Mar 2019 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/9299 2019-03-26T00:00:00Z http://ir.bdu.edu.et/handle/123456789/9298 THE EFFECT OF APRON SPACER AND TOP ROLLER PRESSURE ON 20Ne OF RING SPUN YARN QUALITY To convert cotton fibers into yarn, a considerable number of machines are required. Each and every machine has different parameters, which can be changed to optimize the characteristics of intermediate or final products. Apron spacer size and top roller pressure are considered as some of the major factors that determine the characteristics of the yarn. To properly draft the material adequate contact of top and bottom rollers and proper apron spacing are necessary. In this thesis work the effect of five different spacer sizes i.e. 3.0mm, 3.25mm, 3.5mm, 3.75mm and 4.0mm by varying the top roller pressure of 2.1bar, 2.2bar and 2.3bar on 100% cotton of 20Ne ring spun yarn has been investigated. The change in cotton yarn properties like irregularity percentage, imperfection level, and tensile strength has also been reported. The process parameters from blow room up to ring spinning are kept identical. The result shows that at closer apron spacer, higher pressure generally improves the irregularity percentage, imperfection level, and tenacity of the yarn. But at wider apron spacer increasing the pressure has an opposite effect on the yarn. The optimum yarn quality has been obtained at top roller pressure of 2.3bar and at spacer size of 3.5mm. Tue, 26 Mar 2019 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/9298 2019-03-26T00:00:00Z http://ir.bdu.edu.et/handle/123456789/9297 STUDY THE PROCESS QUALITY PARAMETERS TO ENHANCE THE QUALITY OF BED SHEET FABRICS AT BDTSC The quality of Bed sheet fabrics can be improved by properly controlling the process parameters during weaving. A 100 % cotton plain woven fabric produced by picanol air jet loom at Bahir Dar Textile Share Company has been studied to examine the process quality parameters. The end breakages were studied in 2 hours for 10 times at five picanol air jet looms based on 1.2, 1.5, 2.0, 2.2 and 2.5 kN warp tension at 500 rpm. End breakages were decreasing up to warp tension 2.0 kN and started to increase beyond 2.0 kN warp tension. The lower end breakage rate was 5.70 at 2.0 kN warp tension. At loom speed of 450, 500, 535, 550 and 600 rpm at 1.8 kN warp tension end breakages were studied. As the loom speed was increasing, the end breakage rates were increasing. An also end breakages were studied based on different loom part at 1.5 kN tension and 600 rpm of speed. The loom has three parts which end breakages were occurred. Based on the results, between weaver beam and drop wires of the loom, the breakage rate was higher due to the frequency of warp crossing. Bed sheet fabric GSM and air permeability were tested under 1.2, 1.5, 2.0, 2.2 and 2.5 kN warp tension at 500 rpm. As warp tension was increasing, bed sheet fabric weights were decreasing but Air-permeability of bed sheet fabrics were increasing. During bed sheet fabric inspections, many fabric defects were detected and analyzed. According to fabric grading results, 66.67 % and 46.67%of the fabrics were meeting export requirement on BDTSC‘s and BTRA norms respectively by using four points grading system. Based on material handlings assessments, contaminations frequently affected bed sheet fabrics. Tue, 26 Mar 2019 00:00:00 GMT http://ir.bdu.edu.et/handle/123456789/9297 2019-03-26T00:00:00Z