Minimization of Defects in Knitted Fabric

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Vol. 2, Issue 3 July 2016 Minimization of Defects in Knitted Fabric Pranjali Chandurkar, Madhuri Kakde, Chitra Patil CTF- MPSTME, Narsee Monjee Institute of Management Studies Shirpur Campus,

A knitting fault can occur at any time and if there is no regular examination of the fabric to detect and rectify such as faults, rejection of substantial quantities of fabric can result.

1 Vol. 2, Issue 3 July 2016 Minimization of Defects in Knitted Fabric Pranjali Chandurkar, Madhuri Kakde, Chitra Patil CTF- MPSTME, Narsee Monjee Institute of Management Studies Shirpur Campus, Shirpur, Dist Dhule. Abstract A fabric defect is any abnormality in the fabric that spoils the aesthetics i.e. the clean & uniform appearance of the fabric and this hinders its acceptability by the consumer. A knitting fault can occur at any time and if there is no regular examination of the fabric to detect and rectify such as faults, rejection of substantial quantities of fabric can result. In view of this the present work aim to minimize the knits defects that mostly arises like needle-line, hole, lycra break, oil stain, sinker mark, knit fly. By doing this study fabric defects like hole, lycra break and knit fly reduced by 26%, 36% and 41% respectively. Keywords: fabric defects, needle line, hole, lycra break, sinker mark, knit fly. Introduction In today s very competitive market, it can be said that quality is the main factor in determining the success or failure of an organization. Quality tools have been used in many textile industries to boost quality particularly in the area of manufacturing processes and support functions. The core objective of the majority of the quality is improvement of quality by reducing variation while producing products which meet predefined or predetermined specifications. Though the raw material is properly chosen and the machines are set and maintained properly, defects are likely to occur in the resulting fabric which should be corrected or prevented from occurring. The objective of this project is to minimize defect in knitted fabric by finding out their root causes and suggesting possible solutions to minimize it. Types of defects in knitting department: 1. Needle line: This needle line is the problem that affects the quality of fabrics which occurs due to needle set in a tight or loose and fails of the yarn in needle. Fig no. 1: Needle line 2. Hole: Due to the machine speed is high, quality pulley setting and fabric tension tight, bad knotting, uneven yarn tension, take down mechanism two tight Fig no. 2: Hole 3. Oil stain: Standard oil range should be 80 drops in one minute. If this range goes out of norm then it will create the serious problem that affect the quality of fabric. One possible reason is the use of excess oil than the actual requirement of the machine. This excess oil spreads on the machine causing high accumulation of fluff at cylinder; this fluff then goes under the needles hook and sinkers which creates oil stains in the fabric. Copyright@CTF- MPSTME Page 13

in fabric, then it considered as a fly contamination.

broken needle hook, mixing of lycra and cotton yarn, wrong positioning of lycra wheel, and improper working of

5: Lycra breaks Fabric Inspection: The principle involved in inspection is the early detection of defects,

2 Fig no. 3: Oil stain 4. Contamination: When dead fibres and foreign material such as dyed fibres, husk, and synthetic fibres are knitted in fabric, then it considered as a fly contamination. So to avoid such type of defect proper machine handling and use air pressure to clean the machine is necessary. Fig no. 4: Contamination 5. Lycra breaks: Such type of fault arise in knitted fabric due to poor quality of lycra yarn used, machine dust, broken needle hook, mixing of lycra and cotton yarn, wrong positioning of lycra wheel, and improper working of feeder system. Fig no. 5: Lycra breaks Fabric Inspection: The principle involved in inspection is the early detection of defects, feedback of this information to appropriate people, and determination of the cause, ultimately resulting in the correction of the problem. Fabric inspection is usually done on fabric inspection machines. These machines are designed in such a way that rolls of fabric can be mounted behind the inspection table under adequate light and rerolled as they leave the table. Defects in a fabric can be seen readily with these machines. Copyright@CTF- MPSTME Page 14

3 Fig. no. 6 Fabric Inspections The main objectives of inspection is - 1. Detection of Defects 2. Correcting of defect or defective garments as early as possible in the manufacturing process so that time and money are not wasted later. There are various fabric inspection systems: a. 4-Point system b. 10-Point system c. Graniteville "78" system a. 4-Point System The 4-point system, also called the American Apparel Manufacturers Association (AAMA) point-grading system for determining fabric quality, is widely used by producers of apparel fabrics and by the Department of Defense in the United States and is endorsed by the AAMA as well as the ASQC. To use this system you have to know following things: 1. Fabric inspection method or preparation 2. Criteria of giving penalty points based on defects and defect length. 3. Calculation method of total penalty points for total defects found in a fabric roll or than 4. A Check sheet or format for recording data 5. Knowledge of different types of defects (how a defect looks and its appearance) Penalty points are assessed to a piece of fabric according to the length of defects measured in inches. Procedure of Four Point System: 1. Fabric inspection is usually done on fabric inspection machineries. 2. These machineries are designed so that rolls of fabric can be mounted behind the inspection table under adequate light and re-rolled as they leave the table. 3. Inspection machineries are either power driver or the inspector pulls the fabric over the inspection table. 4. The defects are located, marked and recorded on an inspection form. 5. Some machinery is equipped to measure the length of each roll of fabric (meter/yard). Table no. 1: Fabric inspection by 4 point system 4 Point system 0-3 inch 1 point 3-6 inch 2 point 6-9 inch 3point Experimental Plan: Material and Method: 9-12inch 4 point This study carried out on circular single jersey weft knitting machine. The present work focused on reducing occurrences of defects in single jersey plain weft knitted fabric. To do this study data collected for fifteen days and subsequently make corrective actions in order to reduce the defects. Table no.2: Yarn characteristics Machine Make Mayer & Cie Type of machine Single jersey circular Machine gauge 28 Cylinder diameter 36 inch Machine speed 25 rpm Type of fabric S/J Lycra The specification of single jersey weft knitting machine is as follows: Table No.3: Circular knitting machine specification Results and Discussion: Fabric inspection report before taking corrective action: Table No. 4: Defects found before taking corrective action Copyright@CTF- MPSTME Page 15

4 Type of defects No of defects Total no. of defects Days Day Day Day Day Day Day Day Day Drop stitch Hole pin hole Needle line Fabric cut Sinker line Lycra missing Yarn float Knit fly Oil line Oil spot Total 407 Table No. 5: Defects found after taking corrective action Total no of Type of defects No of defects/day defects Day Day Days Day 1 Day 2 Day 3 Day 4 Day 5 Day Drop stitch Hole pin hole Needle line Fabric cut Sinker line Lycra missing Yarn float Knit fly Oil line Oil spot Total 339 Fig.No.7: Knitted fabric defects Copyright@CTF- MPSTME Page 16

90 80 70 60 50 40 30 20 10 0 Fabric Defects hole lycra break knit fly Before corrective action After corrective action The maximum fabric rejection takes place due to hole, Lycra break, and knit fly.

5 Fabric Defects hole lycra break knit fly Before corrective action After corrective action The maximum fabric rejection takes place due to hole, Lycra break, and knit fly. To reduce the above said defects machine settings and yarn properties were checked and find out the real causes of defects. To reducing the occurrences of defects possible changes in machine settings was made as follows: 1. Hole: To reduce the hole uniform yarn tension was maintained on all the feeders, the rate of yarn feed should be strictly regulated as per the required stitch length by setting quality pulley at 2.90pt. Researchers study show that about 25% of the faults responsible for downgrading the finished garments refer to the yarn faults. 2. Knit fly: knit fly appear in the form of foreign matter such as dyed fibers, husk, dead fibers etc. in the staple spun yarn or embedded in the knitted fabric structure. Dyed and other types of fibers flying from the adjacent knitting machines cling to the yarn being used for knitting & get embedded in the grey fabric. In order to reduce the frequency of knit fly segregate the autostriper knitting machine and circular knitting machines with plastic curtains to prevent the fibers flying from the neighboring machines, from getting embedded in fabric. Fig 8: Machine covered with plastic curtain 3. Lycra break: This type of knitted fabric defects occurred due to that lycra yarn feed with low tension and fail to catch the lycra yarn by needles. To reduce the lycra break uniform tension should be maintained on lycra yarn, ensured that the feed of lycra yarn to every needle and check auto stop motion should work properly. Copyright@CTF- MPSTME Page 17

Fig 9: check tension on lycra yarn After making the above stated changes on machine, the defects like hole, lycra break and knit fly were statistically reduced by 26%, 36% and 41% respectively.

6 Fig 9: check tension on lycra yarn After making the above stated changes on machine, the defects like hole, lycra break and knit fly were statistically reduced by 26%, 36% and 41% respectively. Conclusion A defect of the knitted fabric is an abnormality which spoils the aesthetics i.e. the clean and uniform appearance of the fabric & affects the performance parameters like dimensional stability etc. There are various types of defects which occur in the knitted fabrics out of which majorly found defects like hole, knit fly and lycra break were studied in this project. The study concluded that after taking the various corrective actions the occurrences of hole reduced from 81 to 68, knit fly reduced from 68 to 40 and lycra break reduced from 75 to 48. By doing this study minimization of the 25% fabric defects takes place. References: 1. David J. Spenser, Knitting technology a comprehensive handbook and practical guide, wood head publishing limited, ambridge England, Third edition, Ebraheem Shady et.al. Detection and classification of defects in knitted fabric structures, Textile Research Journal, April 2006, Vol. 78, No. 4, page no Hemdan A. et.al., Online fabric defect detection and full control in a circular knitting machine, AUTEX Research Journal, Vol.8, No.1, March Sadrei A. H., Fault Detection on Simple Circular Knitted Fabrics Using Wavelet, M. Sc. Project, Amirkabir University Technology, Araujo, M. D., Catarino, A. and Hong, H., Process Control for Total Quality in Circular Knitting, AUTEX Research Journal, Vol 1, No.l, (1999). 6. Semnani D and Sheikhzadeh M (2007): Online Control of Knitted Fabric Quality: Loop Length Control, International Journal of Electrical, Computer, and Systems Engineering, Vol 1, pp Shady E, Gowayed Y, Abou-iiana M, Youssef S and Pastore C (2006): Detection and Classification of Defects in Knitted Fabric Structures, Textile Research Journal, Vol 76, pp Copyright@CTF- MPSTME Page 18

Single Jersey Plain. Single Lacoste. Needle set out. Cam arrangement F K. Needle set out. Cam arrangement F1 F2 F3 F4 K T K K K K K T

Single Jersey Plain. Single Lacoste. Needle set out. Cam arrangement F K. Needle set out. Cam arrangement F1 F2 F3 F4 K T K K K K K T Structure Single Jersey Plain Sample Needle set out 1 1 Cam arrangement F K Single Lacoste Needle set out 1 2 Cam arrangement F1 F2 F3 F4 K T K K K K K T Double Lacoste Needle set out 1 2 Cam arrangement