Denim Weaving-Control of Fabric Defects

Transcription

1 Denim Weaving-Control of Fabric Defects L. C. Patil 1, Tushar C. Patil 2, P. P. Raichurkar 3, Vishnu A. Dorugade 4 G.M. Deesan Tex Fab., Shirpur, 1 Assistant Professor, Centre for Textile Functions, MPSTME, NMIMS, Shirpur. 2 Assocciate Dean, Centre for Textile Functions, MPSTME, NMIMS, Shirpur. 3 Principal, Centre for Textile Functions, MPSTME, NMIMS, Shirpur. Abstract Fabric quality is the important from the view of customer satisfaction. About 90% of the fabric defects in the grey fabric originate during weaving in the loom shed. Denim fabric is highly sensitive for defects, mainly like starting marks (crack and thick place), broken pick, snarl and missing end etc. These kinds of defects are broadly responsible for deterioration of fabric quality. This study mainly emphasized on the control of fabric defects in denim weaving at weaving stage by conducting the trials on the respective machine settings of air-jet loom. (Picanol Omniplus 800). Only those fabric defects or faults which are highly contributing to the rejection percentage are taken for trails. Trials are conducted to control the fabric defects by changing the machine settings such as back rest position for starting marks, air pressure setting for snarl, filter value of filling detector and left hand side cutter timing settings for broken pick. Trial results show significant reduction of above fabric defects and also rejection percentage. Key Words- starting marks, filling detector, filter value. Introduction The term "Denim" has originated from the city of Nimes in France where" Serge DeNimes" was manufactured and adopted as a durable pant fabric in the 1849 California Gold Rush, is one of today s most recognized fabrics. Denim s durability is due to the weave, called at will weave. Twill weaves have great abrasion resistance, meaning the fabric will absorb a lot of friction before it breaks apart. The reason for such great durability is the way the yarns are woven together, one set of yarns floats over another 2 3 set of yarns at regular intervals to create a diagonal textured fabric surface. It is these yarn floats that absorb the abrasion. When the floating yarns are worn away, there are still more yarns underneath to hold the fabric together. Take a look at a pair of worn jeans, and look for places when the float yarns have worn away, exposing the white yarns underneath. The importance of controlling the quality of fabric will be clear if we assess its contribution to the overall mill profitability. In weaving it must be mentionedthatabout90%ofthedefectsingreyfabricoriginatedinloom shed. Therefore it is very essential to control the defects in loomshed. This study has been undertaken to reduce the defects in denim which lead to higher rejection percentage in grey stage. Literature review Value loss is attributed to the defective fabric sold as sub standard, rags etc. And represents the discount that is given in the sale price as compared to that of the sound material. It is evaluated on the sale turnover (100%goodpackingbasis) and is, therefore defined as the difference between the value realization of the products (if the total quantity would have been packed as good quality) and actual realization. The value losses that are expected from different Types of looms are givenintable1. Type of loom Value Loss (%) 1 Non-automatic shuttle looms 8-10% 2 Automatic Shuttle Looms 7-8% 3 Shuttleless weaving machines 2-3% Table 1. Value loss for different looms The first point is to be clear that the quality of the fabric at loom is determined by entire sequence of operations from weaving preparatory to weaving. The approach should be to consider each process in relation to the manner in which it affects the subsequent process and not in isolation. In this context, it should remembered that though the preparatory departments and loom shed both contribute substantially to the fabric quality and loom productivity, the conversion cost of the loom shed is greater than that of preparatory. There should be a systematic and periodic checking of settings of the loom mechanisms and accessories in order to ensure that their contribution to fabric defects is minimum. Copyright@CTF- MPSTME Page 20

2 Recording of Loom wise and Weaver wise Fabric Defects The analyse is should be diagnostic in nature so that it would be possible to detect faulty looms and in efficient weavers that give repetitive type of damage. The data regarding fabric faults from a loom giving excessive defects should be compiled and a suitable statement should be made giving the loom numbers, sort no, nature of defect, shift and data occurrences. This should be sent to weaving department for corrective action. If the fault is due to the loom, the necessary setting should be corrected and if the fault is due to the weaver s negligence, it should be brought to his attention. Control Fabric Defects The possible causes for fabric defects may be listed down as under, Quality of raw material Work skills Machine settings. Here is the emphasis given on respective machine settings to control the fabric defects. Major Fabric Defects occurred in denim fabrics- 1) Starting mark Thin place-a small but abnormal gap between the two picks is seen while starting the loom after a stoppage and where the pick density is lower than normal. Thick place-a stripe in the fabric where the pick density is more than the normal. Fig.1 Thin Place (Crack) Fig.2 Thick Place Causes Improper back re stand drop box setting, head frame height & shed angle set not properly, warp beam calibration not ok. If let-off & take-up unit is disturb. If back rest bearing is damage and TSF (Tension system of filler roller) problem. Remedies Set the back rest & drop box setting properly according to quality. Check let-off & take-up unit is disturbed or not. Proper warp beam calibration is eliminating tension variation on warp ends. Head frame height & shed angle set not properly. Check TSF (Tension system of filler roller). 2) Broken Pick A pick missing from a portion of the width of the fabric. Fig.3BrokenPick Causes &Remedies Filling detector OFF during working. Filter value of filling detector is high. Dust accumulated on filling detector. Check working of FD1 / FD2 feeler. Filter value of FD1 and FD2 should be low as possible. Clean FD1 and FD2 Feeler head. Copyright@CTF- MPSTME Page 21

3 3) Snarl Small loops of weft yarn are weaved in the fabric along with the normal pick. Fig.4Snarl Causes Air pressure of relay valve is low than main valve. Improper catch cord drawing. Improper stretch valve pressure and timing. Improper heald frame height and shed crossing. Play in heald frame. Improper binding of leno yarn. Remedies Air pressure of all nozzles. Check catches cord drawing in and its position. Check stretch nozzle timing and position. Heald frame height and shed crossing. Reed dent gap opposite to stretch nozzle. Filling detect or head condition to check for any damage etc. Binding of leno yarn. Plan of work Material & Method MPSTME Page 22

4 Material The study conducted for different types of sorts of fabric. These are as follows: Sr. No. Warp Count Weft Count EPI PPI Weave Grey width (cm) GSM (OZS) 1. 7OE 6OE / OE 7OE / /36 9OE / OE 7OE / OE 7OE / Table1. Fabric sorts taken for trials. Methods- The all above trials are conducted as per following procedure, 1. At start, the cause wise damage analysis report and loom wise summary of weaving defects report has been collected from inspection and packing department. 2. Then analyze causes of defect and there percent of rejection from packing report. 3. The loom wise summary and sort wise summary of weaving defects report on the incidence of damage should also be examined to identify consistently poor performance. 4. Then take a trials of machine settings which responsible for occurrence of damage in denim fabric. 5. Similarly, quality rounds are taken with trimmer for pick out damage in running fabric. Weaving machine make & model All trials carried on the Picanol Omniplus 800 air jet loom which having Electrical warp stop motion, Optical (Front of reed) FD1 & FD2 (filling detector), Electronic let off and take up etc. These trials were conducted by keeping all other parameter as it is and only change the variable. Collection of Monthly Rejection Data Average fabric rejection percentage of three months. Sr. No. Causes of defect Average 1 Starting mark (%) 12 Thick place Curly(Crack) Broken pick Snarl Pick catch Missing end Total 0.280% Table2.CausewiseDefectMonthly Rejection Data Graph No.1 Defect wise before rejection %. Copyright@CTF- MPSTME Page 23

5 The graph shows that defect wise fabric rejection percentage. In denim generally starting mark, Curli, Thick place, broken pick, Snarl, Pick catch and Missing end contributes to higher rejection. Experimental Work- Starting mark - Collection of data from all (112) looms Average settings found on looms for 2/1 and 3/1 twill quality in loom shed for weaving denim fabric Average back rest Height +12 Average back rest Depth +4 Average drop box Height -2 Average drop box Depth +11 Trial Change of back rest setting Faults Back rest Height + 13 Back rest Height + 12 Starting mark 0.022% 0.015% Thin place 0.072% 0.059% Thick place 0.01% 0.012% Table.7 Result of Change in back rest setting result Graph No. 2 Defect wise rejection by changing back rest position The graph shows that by changing back rest height from +13 t o+12, fabric rejection due to starting mark and curli goes on decreasing but slightly increasing thick place. Broken Pick- Follow up of FD2 (filling detector) OFF which responsible for occurrence of broken pick in denim fabric mainly, so FD2 should be ON always. Follow up of filter value of FD1 and FD2 OFF which again responsible factor for occurrence of broken pick in denim fabric. Filter value of FD1 should be 500 µs and filter value of FD2 should be 3000µs. Because as filter value of filling detector increases its sensitivity goes on decreasing, it cannot sense filling yarn. Trial and Result- Change in filter value of filling detector Sr. No. Defect Filter value 5000µs Filter value 3000µs 1. Broken Pick 0.052% 0.016% Table No. 8 Change in filter value of filling detector result Copyright@CTF- MPSTME Page 24

6 Graph No. 3 Results of change in filter value on broken pick The graph shows that by decreasing filter value of filling detector causes decreasing in fabric rejection due to broken pick, because as filter value of filling detector increases its sensitivity goes on decreasing, it cannot sense filling yarn. Snarling Defect- Follow up of count wise pressure settings of main valve, auxiliary valve, Left relay valve, Right relay valve which responsible for occurrence of snarl in denim fabric. Standard air pressure for different counts is as follows. Count Main valve Air pressures (bar) L.H.S. Relay valves R.H.S. Relay valves 6OE OE s(3) s(33) OE+7s(33) OE Table. 9 Count Wise air pressure setting Trial and Result- Effect of Standard air pressure on snarl and fabric quality. Sr. Defect Existing Standard No. Air pressure Air pressure 1. Snarl 0.017% 0.010% Table.10 Changes in Air Pressure Result Graph No.4 Results of Change of Air Pressure for snarling defect. The graph shows that effect of by keeping standard air pressure of main valve and relay valve causes decreasing in fabric rejection percentage due to snarl, because if the pressure of main valve is higher than relay valves it causes snarl in fabric again proper material quality and proper conditioning of material also contributes to reduce snarl. Copyright@CTF- MPSTME Page 25

7 Final Results of Cause wise Fabric Rejection percentage Sr. No. Defect Before Trial Rejection% After Trial Rejection% 1 Starting mark Curli Thick Place Broken pick Snarl Pick catch Missing end Total Table.13Final Results of Cause wise Fabric Rejection percentage Graph No.7 Cause wise Fabric Rejection percentage This graph shows final result of fabric rejection percentage in which before fabric rejection percent was 0.289% and after fabric rejection percent was 0.205% it means reduction in fabric rejection percentage reduce about 29%. Conclusion During the weaving of the denim fabrics, major fabric defects like starting marks are generated because of improper machine settings. Difference in tension on the warp layers during shedding operation is mostly affected by the position of the backrest roll. From the above work done it has been concluded that loom settings has to be done appropriately to control the fabric defects like starting marks. Trials conducted for the starting marks by adjusting the back rest height from+13to+12 show reduction in fabric rejection from 0.022% to 0.015%. Trials conducted for broken pick by adjusting the filter value of filling detector from 3000µs to 5000µs shows reduction in fabric defect from 0.052% to 0.016%. Trials conducted for snarling defect by adjusting standard air pressure according to weft count shows reduction in snarling defect from 0.017% to 0.010%. As an average of all trials shows reduction in fabric defect in denim from 0.289% to 0.205% that means reduction of fabric defect about 29%. This will helpful to increasing realization of fabric by reducing rejection percent occur due to fabric defect and also helps to reduce the manufacturing cost of the fabric. Reference [1] M. K. Talukdar, D. B. Ajgaonkar modern weaving technologies quo Vadis? state of the art report-7, National Information Centre For textile And Allied Subjects (NICTAS), May1998, page No-56. [2] M. C. Paliwal., ATIRA-Process Control in Weaving Page No (Ahmadabad Textile Industry Research Association). [3] Talukdar, Srirumulu and Ajgaonkar. Weaving Machines Mechanisms Management. Page No [4] Pramod Raichurkar, M. Ramachandran, Recent Trends and Developments in Textile Industry in India, International Journal on Textile Engineering & Processes 1 (4), 2015, Page No Copyright@CTF- MPSTME Page 26

8 [5] Vidyarthi S. P. Weaving Defects-Weaving Tablet of Automatic Loom. Page No [6] Sateesh Belemkar, M. Ramachandran, Recent Trends in Indian Textile Industry-Exploring Novel Natural Dye Products and Resources, International Journal on Textile Engineering and Processes 1 (3), 2015, Page No [7] Sabit Adanur Handbook of Weaving Sulzer CRC press, page No [8] R. S. Chauhan, Vrunda Wala Fabric Defects Causes and Analysis Ahmadabad Textile Industry Research Association 2009, Page No [9] Giovanni Castelli, Salvatore Maietta, Giuseppe Sigrisi, Ivo Matteo Slaviero Reference Book of Textile Technology Weaving Italian Association of Textile Machinery Producers Moral Body, October 2000, Page No [10] Trouble shooting in Airjet looms for Denim. [11] M. Ramachandran, Application of Natural Fibres in Terry Towel Manufacturing, International Journal on Textile Engineering and Processes, 1(1) 2015, pp Copyright@CTF- MPSTME Page 27