A study on measures to reduce infrequent yarn faults - Development of an attachment

Transcription

1 Indian Journal of Fibre & Textile Research Vol. 20, December 1995, pp A study on measures to reduce infrequent yarn faults - Development of an attachment A Kanthimathinathan; M Kathirvel, K Gnanasekar, R Hariharan & K P Chellamani The South India Textile Research Association, Coimbatore , India Received 14 February 1995; revised- received and accepted 1 June 1995 A device has been designed and fabricated to be used at the back zone of ring frame to control the high incidence ofiong thin faults, particularly at wider back zone settings. Trials conducted with this device show a significant reduction (about 70%) in long thin and thick faults. Use of this device at the back zone of ring frame does not affect the yarn evenness. However, Uster thin and thick places show a significant reduction. Mill level trials also confirm the above findings. Keywords: Back zone setting, Classirnat faults, Fault control bar, Roving twist multiplier 1 Introduction Detailed surveys of the mixing and yarn quality in more than I()()mills exporting yarns and fabrics have been done! by CfRAs during As per SITRA survey, the overall quality of export yarns corresponds to Uster 57% rating in coarse counts, 70% rating in medium and fine counts and 84% rating in superfine counts. The various infrequent yarn faults measured by the Uster Classimat System are also very high. In coarse and medium counts, the infrequent faults on an average meet Uster 70% standards and in fine counts, the fault level corresponds to as high as Uster 85% standards". Shah- has shown that long thin faults (H + I) are manyfolds higher than Uster 50% levels. Best values of long thick faults (E + F + G) compare well with Uster 25% levels in most of the cases but the average values of these faults are worse than even 50% Uster levels. Substantial reduction in Classimat faults is reported to occur" by using a narrow bottom front zone setting in speed frame. In ring frame, wider top front zone setting results in excessive Classimat yarn faults. But, in this study, no mention is made about the effect of wider back zone setting in ring frame. The survey" by SITRA on "Measures to produce yarns meeting international quality standards for export" has shown that use of wider back zone setting in ring frame (-65 mm) and lesser breakdraft ( ) is prevalent in most of the mills covered in the survey. It has also been observed that wider back zone setting with lesser break draft improves yarn quality in terms ofuster imperfections. However, the effect of wider back zone setting in ring frame on Classimat long length faults has not been covered in this survey. Hence, the present study has been undertaken to study the effect of wider back zone setting in ring frame on long length Classimat faults, and to suggest measures to control long length Classimat wider back zone settings in ring frames. faults at 2 Preliminary Study on the Influence of Back Zone Setting in Ring Frame on Frequent and Infrequent Yarn Faults To reconfirm the influence of wider back zone settings in ring frame on Uster imperfections and long length Classimat faults, this study was conducted for three counts, viz. 30s K, 40s K and s K. Evenness and imperfections at three different back zone settings in ring frame (Table I) clearly show that there Table I-Evenness and imperfections at different back zone settings Count Back zone Evenness Uster imperfections/itxn) m setting U% mm Thin & thick places Neps 30s K s K sk

2 KANTHIMATHINATHAN et af.. MEASURES TO REDUCE INFREQUENT YARN FAULTS 177 is a distinct trend for the evenness and imperfections to improve with wider back zone settings in ring frame. Even though the difference in evenness and imperfections at mm and mm of ring frame setting is not statistically significant in individual cases, the difference becomes highly significant taking all the counts together. This means that the improvement in evenness and imperfections with wider ring frame back zone setting is real and consistent. In the case of wider back zone setting with optimum break draft, twist in roving is broken up in a more gradual manner which, in turn, helps to avoid undrafted ends and short slubs in the yarn. If the slub is of a very high magnitude, it results in end breaks. On the other hand, if the slub is of a smaller magnitude, it is incorporated in the yarn and counted as Uster imperfections. However, the large scale adoption of wider back zone setting in ring frame critically depends on its influence in infrequent yarn faults which are important from the point of view of the performance of the yarn in weaving preparatory as well as during the weaving and knitting processes and the appearance and appeal characteristics of the fabrics. The long thin and thick faults in yarn at different back zone settings are given in Table 2. Both long thick and thin faults increase with wider back zone setting in ring frame. Between mm and mm of back zone settings, the increase is rather statistically significant. The probable reason for the increase in long thin and thick faults at wider back zone setting could be the relatively high level of short fibre content in Indian cottons. The high short fibre content in Indian cottons is supposed to result in some uncontrolled fibre movement in the back zone. This uncontrolled fibre movement creates mass variations at the back zone which are extended in length by the amount of draft in the main zone of the ring frame. Hence, these mass variations are counted as infrequent long thick and thin faults. Therefore, unless some mechanism/method is devised to control the movement of short fibres in the back zone.and thereby to control the tendency of Classimat faults to increase with wider back zone setting, the benefit of using wider back zone setting towards producing yarns with less imperfections can not be fully realized. 3 Design and Development of a Fault Control Bar (FeD) In almost all the modern drawframes,an attachment is provided at the front zone to control the movement of fibres during drafting. Adoption of a similar concept may help to control fibre movement at the back zone of ring frame and thereby to control the tendency of Classimat faults to increase at the wider back zone setting. Accordingly, a fault control bar has been designed and fabricated. However, towards optimizing the configuration of FCB, 4 different designs were made and their effect on Classimat faults evaluated. The 4 designs made are shown in Fig.l. Exhaustive studies made using 4 different bars showed that FCB of the type shown in Fig.1 c gives better results. The results are given in Appendix I. FCB-I C was used for further large-scale trials. The positioning of FCB in the drafting zone of ring frame is schematically-shown in Fig.2. The device consists of a holder (I) which is clamped to the arm bar of the drafting system in the ring frame. The holder holds the long bar (2) which is projected towards the drafting system between top arms. The fault control bar (3) is connected to this long bar with the help of a setting unit (4). The FCB could be positioned in between the middle and back bottom rollers at a raised level to the line offlow of material. The FCB extends over the length between the roller stands. 3.] Effect of FCD on Classimat Faults Using FCB, two counts, viz. 40s K and 40s C, were produced. 40s Combed yarn was produced with 18% noil extraction. The major process parameters are Table 2-Long thick and thin faults-at different back zone settings Count Back zone setting mm Long thick faults Long thin faults (E+ F+G)/Iakh m (HI + II)/Iakhm 30s K 40s K s K Fig. I-Designs of fault control bar

3 178 INDIAN J. FIBRE TEXT. RES., DECEMBER 1995 given in the Appendix II. Classimat long thick and thin faults for the two counts while using FCB in ring frame are given in Table 3. In this experiment, ring frame back zone setting was maintained at mm. For comparative purposes, Classimat faults without using FCB in ring frame are also given in Table 3. At mm setting, while using FCB the long thin faults decreased by about 80% and the long thick faults by'about % as compared to that obtainable without using FCB in 40s K yarn. It may be seen from Table 2 that in medium and fine counts, Classimat long thick and thin faults, on an average, increase by about 70% when the back zone setting in ring frame is increased from mm to mm. Hence, the broad indication is that the level ofclassimat faults (long thin and long thick) at mm back zone setting with FCB is more or less equivalent to that obtained at mm back zone setting without FCB. In the case of 40s carded yarn, while using FCB the long thick faults decreased by 75% and the long thin faults by 40%. The extent of decrease in faults here is rather low as compared to that in 40s K. This is due to the fact that the basic level oflong thin faults itselfis lower in 40s C. This is again attributed to the relatively lower level of short fibre content in 40s C mixing. 3.2 Effect of FCB on Evenness and Uster Imperfections It has been established beyond doubt from the above studies that the introduction of FCB helps to decrease the Classimat long thin and thick faults substantially. However, to find out the effect of FCB on evenness and imperfections, a controlled study was conducted for two counts and the results are presented in Table 3. It is evident from this table that the use of FCB decreases the Uster imperfections (thin and thick), on an average, by about 50% in addition to decreasing the Classimat long thick and thin faults. The effect of FCB on evenness is not significant. Fig. 2-A device for the reduction of long length faults in ring frame [l-holder, 2-long bar, 3-fault control bar, and 4-setting unit) 3.3 Effect offcb on Long Leogtb Faults While Using Roving with Higher Twist Multiplier Shah" has shown that the frequency of long thin and thick faults decreases by about 30% with the use of higher roving twist multiplier. No draft problems were observed on the ring spinning machine in the case of roving material having higher twist levels. It was, therefore, considered of interest to see the influence of FCB on yarn faults while using roving with higher TM. Accordingly, a study was conducted with a higher roving TM of 1.4 (Count, 40s K, Table 3-Effect of FCB on classimat faults, evenness and Uster imperfections Count Back zone Long thick faults Long thin faults Evenness Imperfections/IOOO m setting (E + F + G)/Iakh IT. (HI + lj)j1akh m (U%) rom Thin & thick places Neps Wihtout With Wihtout With Without With FCB FCB FCB FCB FCB FCB Without With Without With FCB FCB FCB FCB 40s K s C Table 4-Effect of FCB while using roving with higher twist multiplier for 40s K count Roving TM Back zone setting rom Classimat faultsl1akh m Uster imperfections/looo m Long thick Long thin Thin & thick places Neps Wihtout bar; and -With bar

4 KANTHIMATHINATHAN et ai.. MEASURES TO REDUCE INFREQUENT yarn FAULTS 179 Table 5-Mill level trials using FCB Mill Count Ring frame Long thick fault: Long thin faults No. back zone (E+ F+G)/ (Hl+ II)! setting lakh m lakhm mm 38s Hosiery ,3 2 50s Carded warp s Combed At wider ring frame back zone settings, the Uster imperfections, particularly thick and thin places, decrease, probably due to the gradual breaking up of twist in the roving. However, the Oassimat long thin and thick faults increase, probably due to the uncontrolled movement of short fibres during drafting. 5.2 The tendency of Classimat long thick and thin faults to increase at wider back zone setting of ring frame is controlled by the use of fault control bar (FeB) designed and fabricated at SITRA. S.3 Use of FeB at ring frame decreased the long thin faults by -80% and the long thick faults by about 70%. -Without bar; and W~With bar Nominal TM, 1.25) and the results are given in Table 4. It is observed that by using FeB, long thin and thick faults decreased by about % in 40s K yarn even when roving with higher TM is used. It may, however, be noted that the extent of decrease (%) in Classimat faults due to FCB (for roving of higher TM) is slightly on the lower side as compared to that obtained while using roving of nominal TM (70%). However;further studies are required to confirm this trend. While using roving of higher TM the imperfections also decrease (about %) due to the incorporation of FeB in the back zone of ring frame. It is of interest to note that the extent of decrease in imperfections at higher level of rovingtm is more or less same as that obtained in the case of normal roving TM while using FeB. Hence, irrespective of roving TM (within the range covered), FCB helps to control long length faults as well as Uster imperfections. 4 Mill Level Trials To supplement the finding at SITRA pilot mill, trials were conducted in 3 member mills of SITRA with and without using SITRA's FCB in ring frame. The counts produced include 38s carded hosiery, 50s carded and s combed. The results are given in Table 5. It is observed that s combed yarn shows substarnial reduction in terms of long thin and thick faults on incorporation of SITRA's FCB at the back zone of the ring frame. The extent of decrease is 50-65% in long thin faults and4o-50o/~ in long thick faults in all. the three mills. 5 Conclusio~ 5.4 FCB also decreased the Uster imperfections. While using FCB at mm back zone setting, the various yarn imperfections, on an average, decreased by about 50%. 5.5 While using a roving of 1.40TM (normal TM, 1.25), FCB decreased the Classimat long thin and thick faults by about %. 5.6 Mill level trials also, by and large, confirm the findings ofsitra pilot mill studies. In mill level trials, by incorporating FeB at the ring frame, long thin and thick faults decreased by more than 50%. Acknowledgement The authors are thankful to MrT V Ratnam, Advisor, SITRA, for guidance throughout this work and to Mr K Sellamuthu, General Manager, Sree Shanmughavel Mills, Dindigul, for permission to conduct the experiments in their mills and also to use the testing instruments at their R&D laboratories. They are also thankful to two other member mills for conducting trials using FeB at their units and to their colleagues, particularly Mr N Ramakrishnan, in Spinning and Textile Physics Division for help at various stages of this project. References I Measures to improve the quality of export yams. A joint report of ATIRA, BTRA, SITRA and NITRA (BTRA, Bombay) Seshadri S & Ramakrishnan N, A study on the quality of export yams, SITRA resea~ch report. 36(7) (1991). 3 Shah P H, Measures for reducing long thin faults in cotton yams through appropriate actions at speed and ring frames. Proceedings of the 34thjoint technological conference of A TI RA. BTRA. SITRA and NITRA (ATIRA, Ahmedabad), Chellamani P, Kanthirnanthinathan A & Karthikeyan S, Measures to produce yarns meeting international quality standards for export. Mill control report No.7 (SITRA, Coimbatore), April 1991.

5 180 INDIAN J. FIBRE TF.XT. RES., DECEMBER 199'1 AppeDdix I-Putiealars ofabe optimizatioil IriaI ofabe deslp of FCB [Count, 30sC; Drafting system- SKF PK 225;Backzone setting at ring frame, mm; and Break draft,l.3] Classimat Without With bar fault type bar A B C Short thick 4769 Long thick 64 Long thin D Appeadix II-Major.pMCe18parameten adopted Process parameter 40s K 40s C Card sliver hank, Ne Comber noil extraction, % Finisher drawing sliver hank, Ne Roving hank, Ne Roving TM Ring frame back zonesetting"mm Spindle speed, rpm Oand7~ "----