FIBRES & TEXTILES in Eastern Europe July / September 2005, Vol. 13, No. 3 (51) 78 n Introductıon Ginning is the frst effective process of cleaning and separating the impurities and seeds from the cotton. After the cotton has been picked, it is taken to the ginning-mills, where the fbre, called cot- ton lint in the trade, is separated from the seed. Ginning processes are important in determining the cotton fbre quality for the production of cotton yarn. The measured and unmeasured cotton fbre properties may be identifed as follows: length, strength, elongation, cleanness/cleanability, fneness and ma- turity, sugar content, motes, neps, fbre maturity, stickiness, contamination, seed coat fragments, dead cotton, cavitoma. The only characteristics infuenced by the ginner are length, neps and foreign matter. Also, the fbre moisture during ginning, the amount of cleaning used and the gin housekeeping practices infuence the cotton fbre’s characteristics [1]. Hughs reviewed the ginning literature for saw-gin and roller-gin machines. Lint cleaners are very important in determi- ning the quality of cotton. Lint weight, mean length, short fbres, neps and yarn strength are infuenced by lint cleaners. The effect of lint cleaners can be sum- marised as follows: card web nep counts, short fbre content and dyeing problems may increase; yarn appearance, staple length and strength decrease as the amo- unt of lint cleaning increases. [2]. Ginning mills are divided into saw-gin mills and roller-gin mills. The processed cotton is named after the looms used, thus saw-gin cotton or roller-gin cotton. The working principles of these two machines are different from each other. In general, the structure of the roller- gin machine is rather simple. However, labour expenses are much more than those of saw-gin machines, as these are more complex than roller-gin machines. Harmancıoğlu found in his investigations that saw-gin cotton was more suitable for spinning coarse yarn, and roller- gin cotton was suitable for fner yarns. These two ginning processes have little effect on the strength of the yarn [3]. The roller gin is a slow working machine and processes 60 to 80 kg of seed cotton per hour. However, saw gins can process 600-800 kg per hour. Roller-gin machi- nes has minimal pre-cleaning equipment, and the lint contains leaf and trash. Saw- gin machines, on the contrary, have a great deal of pre-cleaning equipment for seed cotton and lint cleaners after cleaning [4]. It is very diffcult to estimate the cost of ginning, and data on ginning costs is not available from all the cotton producing countries. However, Chaudry [5] consi- dered the cost of ginning in many count- ries in the light of the transportation cost to the ginning factory, the fee for classing and grading the cotton, and the cost of other expenses related to ginning. It was shown that the ginning cost was highest in Spain, at US$549 per ton of lint, whereas the lowest cost was in China, at US$25 per ton of lint. The mean value of ginning cost in selected countries was US$240. Mangialardi & Anthony discussed the characteristics and effciency of fow- through air-type lint cleaners. It was mentioned that improved air-type lint cleaners, by adding a second stage of saw-type lint cleaning, might be suffci- ent for lint cleaning with one saw cylin- der lint cleaner [6]. Kechagia [7] has outlined the conditions and requirements to be met in quality cotton production as well as the relevant practices in exami- ning the optimisation of the ginning pro- cess. Several recommendations for better ginning operations in cotton procedures and for industry-government organisati- ons were also made. Chaudhry [5] alsoexamined the existing number of saw-gin and roller-gin looms used worldwide. The roller-gin and saw- gin looms used in selected cotton pro- ducing countries were investigated. Ac- cording to the paper, India has the most roller-gin looms with 46,529 looms and the USA leads in using saw-gin looms, with 1275. The distribution of ginning cotton systems in selected countries in percentages has also been investigated by Chaudhry, concluding that saw-gin ginning machines were slightly more preferred to roller-gin machines. Dorais- wamy et al. examined the roller gin and saw gin machines, and their characteristic differences & process stages in detail [8]. Both ginning operations include pre-gin- ning equipments and lint cleaners. The aim is to condition, clean and prepare the seed cotton before ginning. The feed rate of seed cotton from the separator to the ginning machine infuences the lint produced. The saw or roller speed also infuences the quality of lint produced. In saw-gin ginning machines, the cotton fbre is separated by the saw, instead of the roller in the roller-gin machine. Saw- gins are divided into air blast gin and brush gin according to the type of the stripper. The brush-type ginning machine is preferred in high-capacity machi- nes [9]. Further studies were carried out elsewhere by introducing general desc- Theoretical Investigation of Separator Units in Saw-gin Machines. I: Cotton Flow Rate Estimation Erdem Koç, Oğuz Demiryürek Çukurova University, Textile Engineering Department, Adana, Turkey Abstract This theoretical study is intended to investigate the performance of a saw-gin ginning machine with special reference to separator units. For this purpose, a theoretical model of the separator units of a particular saw-gin machine has been developed by introducing the non-dimensional parameters defning the mechanical operating conditions, and we have also outlined a design procedure whereby the cotton fow rate and loss of cotton can be estimated in such a system. This paper forms part of an extended theoretical investigation into the separator units of saw gin machines; here, only the fow rate estimation results obtained for the frst unit of the separator have been discussed. Keywords: ginning process, saw-gin, separator units, non-dimensional fow rate.