International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 125 Customization of Starfish Technology in the Production of Cotton-Knit Fabrics: A Practical Approach A.K.M. Mobarok Hossain1 , Dr.A.B.M. Zohrul Kabir2 1 Assistant Professor, Department of Textile Technology, Ahsanullah University of Science and Technology, Dhaka, Bangladesh 2 Professor,Islamic University of Technology,Gazipur,Bangladesh Abstract -- Demands for Cotton-knitted garments have been increasing steadily since 70s as consumers worldwide recognized their comfort and adaptability for all types of regular, leisure and sportswear. While processing order for the buyer, knit-garment makers generally specify their requirements in terms of grams per square meter (GS M), fabric width and shrinkage (both length and width),based on mostly buyer’s requireme nts and processing capability; for a finished knitted fabric of a particular shade. The fabric suppliers (particularly the knitters), on their part, have to choose knitting variables like machine gauge (defined by no. of loop-forming needles per unit circumference of the machine), yarn count (a measure of yarn fineness) & stitch length (length of yarn in a loop).The choice of these knitting variables is important in order to meet the quality specification of the buyers. S ometimes the combination of the requirements as demanded on the finished knitted fabric, is quite impossible to achieve. For this reason it is very common for knitted-fabric manufacturers to carry out a fairly large numbers of sample trials when they are required to develop a new product. These trials can consume considerable amount of time and raw materials, and cause considerable disruption to production schedules, before a satisfactory solution is found. Research works have been carried out worldwide for developing a practical system for reliably predicting the shrinkage and dimensional properties of finished Cotton–knitted fabrics. The most recognized effort may be that of IIC (Recent CTI) termed as S TARFIS H. It is a computer program, and a body of know-how which can demonstrate how to engineer cotton circular knits so that the quality and the performance can be right first and on time. To use S TARFIS H with the simplest option , the user has to give input variables of machine gauge, yarn count and stitch length mainly as well as specifying a target value of GS M and fabric width or shrinkage. In case of target GS M and fabric width, the S TARFIS H gives shrinkage as outputs and in case of target shrinkage; the software gives GS M and fabric width as outputs. But as S TARFIS H outputs represent the results developed from many industrial trials of different countries, the user just gets the standard average values of GS M, Width and S hrinkage of a particular fabric from S TARFIS H. S o to customize this software in a particular factory, the results given by S TARFIS H has to be calibrated according to the factory results. Though the software provides a self-calibration method which is more experimental, a quick calibration procedure will definitely be more users friendly and support the application of this software more practically in a real factory situation. In this work, first, the relationship between S TARFIS H inputs (yarn count and stitch length) and outputs (GS M/Width) has been established through a set of multiple linear regression models for each specific machine gauge. The models thus developed have a high degree of correlation ship. Consequently, the regression models can be used as a substitute of S TARFIS H to predict outputs with a high accuracy under similar environment. S econdly S TARFIS H predicted results have been compared with recorded results of Beximco Knitting Limited (A renowned knitting factory of Bangladesh) using standard statistical measures in order to customize S TARFIS H as a real factory case. It was observed that the mean absolute percentage error (MAPE) is less than 5% for all machine gauges. The findings thus clearly establish a quite advantageous approach for applying such technology for the selection of decision variables. Index Term-- Knitting, Gauge, Yarn Count, S titch Length, GS M, S hrinkage 1. INTRODUCTION Knitting is a process of fabric manufacturing by interlocking series of loops of one or more yarns. Knitted fabrics are used to produce garments that cover every part of the human body, in a wide range of garment types from socks, caps, gloves and underwear to upper and lower body garments varying from Tshirts to formal jackets. The dramatic increase in the popularity of knit fabrics during the last three decades provides a vivid example of the interrelationships between lifestyle, technology and fashion. The high degree of stretch and comfort that knit cloth brings to close-fitting garments, coupled with excellent wrinkle resistance, makes them eminently suitable to the modern consumer s demands. Unlike weaving, knitting cannot commence with any type of yarn. Knitting requires a relatively fine, smooth , strong yarn with good elastic recovery properties. Cotton yarn is proven worldwide as particularly suitable for knit garments like underwear, outerwear, sportswear and socks. Though the development of synthetic fibers brought revolution to the clothing industry, cotton-knitted fabrics have always enjoyed great popularity among all kinds of knitted fabrics. Due to unprecedented competition in the global apparel indust ry customers are demanding better quality in terms of improved performance (e.g. lower shrinkage and better retention of shape and performance). The International Institute for Cotton 117801-6464 IJET-IJENS © February 2011 IJENS IJE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 in1988 introduced to the industry the results of an extensive research program into the shrinkage and dimensional properties of finished knitted cotton fabrics. The package is marketed as a computer program called STARFISH. 126 The fabric for this process is invariably knitted on circular knitted machines. These machines vary in diameter , gauge(the number of needles per inch) and production capacity. After knitting it goes to wet processing unit for coloration and minor adjustments in finished dimensions. Also fabric stability and handles are improved in finishing.Garment pieces are cut from finished piece goods fabric, laid up (spread) on to cutting tables . Marker portrays the way in which pieces of a garment are laid out on the fabric for cutting .The marker is laid out to a particular width of a fabric and within an optimum length , and may represent only one size or a mixture of two or more sizes. All parts of the garments other than the trims are cut from the lay. Each garment pieces has all edges cut, hence the term fully cut. The garments are assembled by seaming machines and trims are added where appropriate. 2. OBJECTIVES The objectives of this study can be summarized as follow: To study the STARFISH Technology and its relevance with knit manufacturing. To search for any type of possible relationship between input and output parameters by analyzing STARFISH results. To compare some relevant R&D (Research and Development) records of a standard knit factory with STARFISH outputs with the help of statistical analysis. To propose the calibration for customization of STARFISH for that factory and thus establishing a feasible general way for customization of this technology for all circular weft-knit plants under similar production environment. 3. 2.TRADITIONA L PRODUCT DEVELOPM ENT PROCEDURE PRACTICED BY KNITTING PLANT After getting fabric specification from garment manufacturing unit, knit-plant goes for sample development. A simple flowchart is shown below. 3. THEORITICAL BACKGROUND 3.1.FLOW CHART OF KNITTED GARMENTS MANUFACTURING All knitted garments can be classified into four categories according to general Production methods: (1)Fully cut (2)Stitch shaped cut (3)Fully fashioned (4)Integral Among these fully cut garments cover the widest range of different types of garments, including men's, women's and children's underwear ,swimwear, sportswear and leisurewear. The production sequence of such garments is shown below. Yarn receiving Circular knitting of fabric Scouring, bleaching and/or dyeing Pressing, calendaring or decatizing or stentering (finishing} Marker making Laying up (spreading) of fabric Cutting Assembly Examine and mend Finish press Fabric manufacturing (Knitting) unit Wet processing unit Garments manufacturi ng unit Fig. : Production sequence of knitted garments. 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 127 1. Garments manufacturing unit Function: Supplies fabric specifications, like; A) Fabric type (Plain Jersey, , Rib etc) B) Fiber type (Cotton, Silk, Wool etc). C) Fabric properties (Shade, Shrinkage, GSM, Width etc). 2.Knit- Factory management Function: Gives order to research and development center of the plant for sample development. Takes necessary steps for arranging raw materials and executing sample development. 3.Research and development center of the factory 4. Knitting, dyeing and finishing section Function: Takes sample development program . Search for similar existing R&D records If found If not found Give program for similar development Gives trial sample programs to knitting dyeing and finishing section Submits the sample to the garment manufacturing unit Developed sample is OK (Required properties have been achieved Developed sample is not OK (Required properties have not been achieved) Fig. Rolls of different teams in the research and development (R & D) chain of a knit fabric 117801-6464 IJET-IJENS © February 2011 IJENS IJE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 Note : Sample development programs are totally controlled by factory management for factories which do not have R&D centers 4. EXPERIM ENTAL STEPS The work progressed by completing the following steps sequentially. -Searching records of those specific samples from R&D Department of Beximco Knitting Limited (a renowned and standard Knit factory of Bangladesh), processing of which are very much similar to STARFISH guided processing sequence. -Obtaining simulated test results from STARFISH for two output variables (i.e. GSM and Width) keeping the third output (i.e. Shrinkage) same as the factory result. -Finding out the deviations between STARFISH results and factory results by standard statistical measures. - Finding out mathematical relations between input and output variables by analyzing the STARFISH results with the help of MATLAB and WINQSB software so that those can be u sed anywhere for prediction without the help of a computer. - Forecasting the possible factory outputs with the help of calibrated STARFISH outputs 5. STARFISH COM PUTER PROGRAM The name STARFISH is contracted from the phrase “START as you mean to FINISH” .It embodies the principle that, in order to know how to produce a knitted fabric with the desired dimensions and performance, we must first have an accurate knowledge of the finished product. The STARFISH Kit was first made commercially available in 1988 after several years of preliminary testing and development in the industry. The collection of new data and the development of improved analytical techniques for the interpretation of the data base is being continued by Cotton Technology International (CTI). A simplified operational procedure of STARFISH software (Version 5.03) is shown below Software Operation Presetting : Units Targets (Shrinkage/ GSM & Width) Giving Inputs: Fabric type Yarn type (combed, carded etc.) Knitting machine (specified by gauge, diameter & no. of needles) Yarn count Stitch length Wet process route (Dyeing machine type: Jet, Winch etc.) Nominal depth of shade (White, medium, deep etc.) Target values specified: (Values of GSM& Width /Shrinkage) Getting outputs: (Values of Shrinkage /GSM& Width) 128 Note: ►For a particular fabric of a specified shade, major and dominating inputs are yarn count, stitch length and knitting machine. ►Generally buyer's requirement is more rigid on Shrinkage as it is the most sensitive issue from the consumer's point of view. So shrinkage is generally selected as target. 6. CUSTOM ERS SPECIFICATION AND STARFISH For a finished knitted fabric, the “customer” is the person or organization, which decides the final performance of the product. It may be a store group, a garment maker, a converter or a retail division of a vertical company. The customer usually sets out his requirement in the form of a specification, which calls for combination of properties like* GSM * Width and * Shrinkage Sometimes this combination of properties is quite impossible to achieve in practice. It is a well-known fact that the demands of customers are often based largely upon wishful thinking rather than solid experience of the product that they have in mind. In the case of a new product this is almost inevitably the case and is to be accepted as a fact of life – part of the process of product evolution and improvement in response to market opportunities. But problem arises when the demanded weight, width and shrinkage values are mutually incompatible. Even the customer may ask for better shrinkage on an existing quality without allowing any changes in weight and width! If the manufacturer has access to STARFISH and thus has the calibrated result, then the specification can be checked and the customer can be informed of what it is possible to achieve without depending on sample making. Also the customer may be offered various practical alternatives to choose if he wishes. 7. DATA COLLECTION 7.1 DATA SORTING FROM EXISTING R&D RECORDS OF BEXIMCO KNITTING LIMITED For customization of STARFISH, the first step is to find out those production or sample records, processing of which are very much similar to STARFISH guided processing sequence. For this purpose the most standard and popular knitted fabricPLAIN JERSEY was selected and the recent production and sample records of Beximco Knitting Limited were considered. MS Excel Auto filter Option was used for doing this Also Log books were checked manually for accuracy. The other unique characteristics of these records are1) The fabrics were knitted and processed in Beximco Knitting Limited with the yarn of Padma Textiles Limited- a sister concern of Beximco. So a high consistency is expected in measuring production variables and outputs. 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 2) 3) 4) 129 atmospheric conditions. Therefore, the results achieved are comparable with STARFISH generated results. Samples were knitted in four type of knitting machines and one type of dyeing machine. Knitting machines are of 18G30D (18 Gauge and 30” Diameter}, 20G30D, 24G30D and 28G30D respectively. Dyeing machines are of jet type. Samples were only solid dyed in medium deep shade (between 4-6% dyestuff) and no reprocess or additional chemical treatment was carried out. Samples were subjected to a reference relaxation procedure (similar to that of STARFISH recommendation) for property measurements in standard 7.2 CHART OF APPLICABLE PRACTICAL DATA FROM BEXIMCO KNITTING LIMITED The following tables show the list of all data that were found as standards for the desired purpose .The collected data was arranged knit-machine wise as shown in table (i)to table (iv)for better understanding and implementation. T ABLE I DATA FROM KNITTING MACHINE TYP E : 18G, 30”D, 1728 NEEDLES Knitting Machine Type: 18G, 30" Dia., 1728 Needles Yarn Count Stitch Length GSM Width Length Shrinkage (%) Width Shrinkage (%) 1 15/1 3.32 272 56 5.3 4.3 2 16/1 3.31 231 59.5 3.6 4.2 3 17/1 3.26 231 56 4.3 6 4 17/1 3.38 222 58 4 5 5 20/1 3.14 195 54 2 7 6 20/1 3.02 205 53 5 5 7 20/1 3.07 202 54.5 2.7 6.3 8 20/1 2.78 217 51 3.5 6.8 T ABLE II DATA FROM KNITTING MACHINE TYP E : 20G, 30”D, 1944 NEEDLES Knitting Machine Type : 20G, 30" Dia., 1944 Needles Yarn Count Stitch Length GSM Width Length Shrinkage (%) Width Shrinkage (%) 1 20 2.83 217 58 5 5 2 20 2.79 216 56 5 5 3 20 2.94 200 58 5 5 4 20 3.01 190 60 5 5 5 20 2.9 209 57.5 2.4 6.3 6 22 2.8 200 56 5 5 T ABLE III DATA FROM KNITTING MACHINE TYP E : 24G, 30”D, 2256 NEEDLES Knitting Machine Type: 24G, 30" Dia., 2256Needles Yarn Count Stitch Length GSM Width Length Shrinkage (%) Width Shrinkage (%) 1 20 3.02 207 64 5 2.3 2 20 2.96 202 64 5 5 3 20 3.15 198 69 7 7 4 20 2.91 218 67 2.3 7 5 22 3.1 198 69.5 6 7.7 6 24 2.77 174 64.5 1.7 7.5 117801-6464 IJET-IJENS © February 2011 IJENS 7 24 3 157 70.5 6.8 8.6 8 26 2.63 177.5 61 5 5 I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 130 T ABLE IV DATA FROM KNITTING MACHINE TYP E : 28G, 30”D, 2640 NEEDLES Knitting Machine Type: 28G, 30" 1 Dia., 2640 Needles 26 Yarn Count 2.61 Stitch Length GSM 180 Width 69 Length Shrinkage (%) 4.9 Width Shrinkage (%) 4.2 2 3 4 5 30 2.77 146 68 5 4 30 2.85 144 73.5 3.2 7.2 34 2.69 120 72 8.4 12.5 40 2.45 129 63 9.3 7 the consumer’s point of view it has been specified as target in this project work rather than GSM & width. Tables (v) to (viii) show the STARFISH outcomes for the sorted applicable data obtained from the factory as mentioned in section 7.2 . 7.3 STARFISH GENERATED RESULTS. For making a comparison between original factory output and STARFISH output, similar values of inputs and target to the software were given to get values of outputs. It may be mentioned that as shrinkage is the most sensitive issue from T ABLE V ST ARFISH RESULTS FOR SAME VALUES OF FACTORY INP UTS FROM 18G MACHINES Knitting Machine Type: 18G, 30" Dia., 1728 Needles 1 Yarn Count 15/1 Stitch Length 3.32 GSM (Factory) 272 GSM (Starfish) 240 WIDTH (Factory) 56 WIDTH (Starfish) 61 Length Shrinkage (%) Target 5.3 Width Shrinkage (%) Target 4.3 2 16/1 3.31 231 232 59.5 60 3.6 4.2 3 17/1 3.26 231 216 56 58.8 4.3 6 4 17/1 3.38 222 213 58 60.6 4 5 5 20/1 3.14 195 196 54 57.1 2 7 6 20/1 3.02 205 200 53 54.4 5 5 7 20/1 3.07 202 199 54.5 55.8 2.7 6.3 8 20/1 2.78 217 213 51 52.5 3.5 6.8 T ABLE VI ST ARFISH RESULTS FOR SAME VALUES OF FACTORY INP UTS FROM 20G MACHINES Knitting Machine Type: 20G, 30" Dia., 1944 Needles 1 Yarn Count 20 Stitch Length 2.83 GSM (Factory) 217 GSM (Starfish) 210 WIDTH (Factory) 58 WIDTH (Starfish) 58.6 Length Shrinkage (%) Target 5 Width Shrinkage (%) Target 5 2 20 2.79 216 213 56 58.1 5 5 3 20 2.94 200 204 58 60.1 5 5 4 20 3.01 190 200 60 61.1 5 5 117801-6464 IJET-IJENS © February 2011 IJENS 5 20 2.9 209 209 57.5 60.4 2.4 6.3 6 22 2.8 200 195 56 57.1 5 5 I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 131 T ABLE VII ST ARFISH RESULTS FOR SAME VALUES OF FACTORY INP UTS FROM 24G MACHINE Knitting Machine Type: 24G, 30" Dia., 2256Needles 1 Yarn Count 20 Stitch Length 3.02 2 20 2.96 3 20 3.15 4 20 2.91 5 22 3.1 6 24 2.77 7 24 3 8 26 2.63 GSM (Factory) GSM (Starfish) WIDTH (Factory) WIDTH (Starfish) Length Shrinkage (%) Target Width Shrinkage (%) Target 202 203 64 70.1 5 5 198 185 69 74.6 7 7 218 207 67 70.8 2.3 7 198 173 69.5 72.9 6 7.7 174 183 64.5 66.4 1.7 7.5 157 161 70.5 70.8 6.8 8.6 177.5 177 61 61.4 5 5 207 205 64 69.1 5 2.3 T ABLE VIII ST ARFISH RESULTS FOR SAME VALUES OF FACTORY INP UTS FROM 28G MACHINE Knitting Machine Type: 28G, 30" Dia., 2640 Needles 1 Yarn Count 26 Stitch Length 2.61 GSM (Factory) 180 GSM (Starfish) 179 WIDTH (Factory) 69 WIDTH (Starfish) 70.9 Length Shrinkage (%) Target 4.9 Width Shrinkage (%) Target 4.2 8. DATA A NALYSIS 8.1 ANALYSIS OF STARFISH PREDICTION SYSTEM STARFISH is commercial costly software and the manual or software itself does not reveal any mathematical technique by which the predictions are generated. It was thought that by considering the major knitting variables as independent variables and software outputs as dependent variables, a multiple linear regression model could be formed. So the three independent variables were taken as knitting machine, yarn count and stitch length and two dependent variables were GSM & width, which were of our interest. Knitting machines located in a particular factory can be divided generally into certain categories. So classifying the data according to knitmachine wise and thus eliminating one independent variable an easily understood model of multiple linear regression model could be formed where independent variables were yarn count and stitch length and dependent variables were GSM & Width taking into mind that shrinkage was our target. Both MATLAB and WINQSB software were used for performing multiple linear regressions. 2 30 2.77 146 151 68 71.3 5 4 3 30 2.85 144 145 73.5 75.1 3.2 7.2 4 34 2.69 120 121 72 74.7 8.4 12.5 5 40 2.45 129 119 63 63.8 9.3 7 independent variables for a particular gauge were taken as inputs. Then for each pair values of yarn count and stitch length, values of dependent variables i.e. GSM and width from STARFISH software were taken as outputs. The detailed operation sheets have been attached in APPENDIX-A. Summarized results of regression models from MATLAB for different specific target shrinkages have been shown in table (ix)to (xii) which are arranged based on knitting machine type i.e. gauge wise. The first row of a table shows the target shrinkages obtained from a similar type of table of section 7.3 and other rows show the corresponding regression results. 1. Knitting Machine Type: 18 gauge, 30 inch dia., 1728 needles (18G 30”D 1728N) Input range Yarn Count (Ne) = 14-22 ; Selected values : 14, 16 ,18, 20, 22, 24 Stitch Length (mm) =2.78-3.38 ; Selected values : 2.78, 2.96, 3.14, 3.32, 3.38 8.2 APPLICATION OF MATLAB MATLAB is a high performance language for technical computing. In this thesis work MATLAB has been employed to build multiple regression models for each specific target shrinkage of a particular gauge machine.To work with this software, at first, some randomly selected values of yarn count and stitch length that covers the full practical range of these 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 132 T ABLE IX SUMMARIZED RESULTS FROM MAT LAB REGRESSION MODELS FOR 18G MACHINE Note : 1. Output Target (Length GSM Shrinkage and Regression Width Regression coefficient Max Shrinkage) coefficient for Constant for stitch Err. yarn count length Width Regression Regression coefficient coefficient Max Constant for yarn for stitch Err. count length 5.3%X4.3% 3.6X4.2% 4.3%X6% 4%X5% 2%X7% -11.12 -11.32 -11.02 -11.16 -11.18 -58.08 -59.56 -57.58 -57.98 -58.79 601.47 614.1 596.54 603.38 606.09 10.68 10.95 10.81 11.04 10.88 -0.629 -0.628 -0.64 -0.634 -0.648 5%X5% 2.7%X6.3% 3.5%X6.8% -11.08 -11.16 -11.02 -57.89 -61.32 -57.58 599.34 613.15 596.54 10.71 10.56 10.81 Approximately suitable count for a particular type of machine (Gauge): (Gauge) 2 Ne = 18 If Gauge = 18, then Ne = (18) 2 /18 =18 2. 3. Practically used/useable count range in 18 gauge machine = 14-22 Machine setting (VDQ No.) for minimum and maximum stitch length in existing 18 Gauge machines are 140 and 163 respectively. 2. 12.29 12.32 12.565 12.403 12.715 29.45 29.251 29.802 29.593 30.101 0.421 0.415 0.446 0.375 0.408 -0.634 12.403 29.593 0.375 -0.643 12.908 29.039 0.532 -0.644 12.689 30.057 0.4 · If VDQ = 115, then Stitch Length = [115 X 41.8(Constant)]/1728(No. of needles) = 2.78 · If VDQ = 140, then Stitch Length = [140 X 41.8(Constant)]/1728(No. of needles) = 3.38 Knitting Machine Type: 20 gauge, 30 inch dia., 1944 needles (20G 30”D 1944 N) Input range Yarn Count (Ne) = 18-28 ; Selected values: 18, 20, 22, 24, 26, 28 Stitch Length (mm) =2.47-3.11 ; Selected values: 2.47, 2.63, 2.79, 2.95, 3.11 T ABLE X SUMMARIZED RESULTS FROM MAT LAB REGRESSION MODELS FOR 20G MACHINE Output Target (Length GSM Shrinkage and Regression Width Regression Shrinkage) coefficient for coefficient Constant for stitch yarn count length 5% X5% 2.4%X6.3% -7.57 -7.7 -55.73 -56.25 522.26 529.20 Max Err. 9.73 10.33 Width Regression Regression coefficient coefficient Constant for yarn for stitch count length -0.507 -0.517 13.521 13.698 30.398 30.897 Max Err. 0.470 0.5 Note : 1. Approximately suitable count for a particular type of machine (Gauge): (Gauge) 2 Ne = 18 If Gauge = 20, then Ne = (20) 2 /18 =22.22 ≈ 22 3. Machine setting (VDQ No.) for minimum and maximum stitch length in existing 20 Gauge machines are 115 and 145 respectively. · If VDQ = 115, then Stitch Length = [115 X 41.8(Constant)]/1944(No. needles) = 2.47 · If VDQ = 145, then Stitch Length = [145 X 41.8(Constant)]/1944(No. of needles) = 3.11 2. Practically used/useable count range in 20 gauge machine = 18-28 3. Knitting Machine Type: 24 gauge, 30 inch dia., 2256 needles (24G 30”D 2256 N) 117801-6464 IJET-IJENS © February 2011 IJENS IJE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 133 Input range Yarn Count (Ne) = 20-32 ; Selected values : 20, 22, 24, 26, 28, 30, 32 Stitch Length (mm) =2.59-3.02 ; Selected values : 2.59, 2.71, 2.80, 2.91, 3.02 T ABLE XI SUMMARIZED RESULTS FROM MAT LAB REGRESSION MODELS FOR 24GMACHINE Output Target (Length GSM Shrinkage and Regression Width Regression coefficient Max Shrinkage) coefficient for Constant for stitch Err. yarn count length Width Regression Regression coefficient coefficient Max Constant for yarn for stitch Err. count length 5% X2.3% 5%X5% 6.8%X8.6% 1.7%X7.5% 7%X7% 6% X7.7% 2.3% X7% -0.521 -0.536 -0.559 -0.553 -0.548 -0.551 -0.548 -6.15 -6.00 -5.65 -6.03 -5.75 -5.76 -6.03 -50.14 -49.34 -46.49 -49.87 -46.78 -47.57 -49.48 476.83 466.01 439.06 469.49 445.05 448.19 468.38 Note : 1. Approximately suitable count for a particular type of machine (Gauge): (Gauge) 2 Ne = 18 If Gauge = 24, then Ne = (24) 2 /18 =32 2. Practically used/useable count range in 24 gauge machine = 20-32 3. Machine setting (VDQ No.) for minimum and maximum stitch length in existing 24 Gauge machines are 140 and 163 respectively. 7.97 7.86 7.28 8.32 8.04 7.24 8.50 14.407 14.879 15.497 15.215 15.218 15.268 15.219 35.563 36.372 37.762 37.609 37.127 37.540 37.127 0.457 0.507 0.516 0.498 0.477 0.472 0.477 · If VDQ = 140, then Stitch Length = [140 X 41.8(Constant)]/2256(No. of needles) = 2.59 · If VDQ = 163, then Stitch Length = [163 X 41.8(Constant)]/2256(No. of needles)= 3.02 4. Knitting Machine Type: 28 gauge, 30 inch dia., 2640 needles (28G 30”D 2640 N) Input range Yarn Count (Ne) = 26-40 ; Selected values : 26, 30, 32, 34, 40 Stitch Length (mm) =2.45-2.93 ; Selected values : 2.45, 2.57, 2.69, 2.81, 2.93 T ABLE XII SUMMARIZED RESULTS FROM MAT LAB REGRESSION MODELS FOR 28GMACHINE Output Target (Length GSM Shrinkage and Regression Regression Width Shrinkage) coefficient coefficient Max Constant for yarn for stitch Err. count length Width Regression Regression coefficient coefficient Max Constant for yarn for stitch Err. count length 3.2%X7.2% 8.4%X12.5% 9.3%X7%% 5%X4% 4.9% X4.2% -0.497 -0.524 -0.496 -0.480 -0.480 -3.88 -3.48 -3.66 -3.96 -3.97 -43.5 -38.5 -40.67 -44.17 -43.83 387.62 345.74 363.73 393.95 393.41 5.81 5.21 5.99 6.15 6.23 16.6 17.617 16.667 16.133 16.1 117801-6464 IJET-IJENS © February 2011 IJENS 42.688 45.171 42.327 41.041 41.240 0.541 0.541 0.531 0.475 0.465 I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 Note : 1. Approximately suitable count for a particular type of machine (Gauge): (Gauge) 2 Ne = 18 If Gauge = 28, then Ne = (28) 2 /18 = 43.5 ≈ 43 or 44 2. Practically used/useable count range in 28 gauge machine = 26-40 3. Machine setting (VDQ No.) for minimum and maximu m stitch length in existing 28 Gauge machines are 155 and 185 respectively. · If VDQ = 155, then Stitch Length = [155 X 41.8(Constant)]/2640(No. of needles) = 2.45 · If VDQ = 185, then Stitch Length = [185 X 41.8(Constant)]/2640(No. of needles) =2.93 8.3Exploring means of MATLAB result 1.By using the values of regression co-efficient for yarn count and stitch length, and intercept a regression equation can be formed .For example, for a target length shrinkage of 2.7% and width shrinkage of 6.3% if existing 18 Gauge machines are used then regression equations for GSM and Width will be GSM = 613.15-11.16 Y.C(Yarn Count).- 61.32 S.L(Stitch Length) Width=29.039- 0.643 Y.C.+12.908 S.L.2. Maximum error represents the maximum deviation between the predicted outputs by MATLAB regression equations and STARFISH original outputs. For example, for a target shrinkage of 7%X7% if existing 24 Gauge machines are used then maximum error for GSM will be 8.04 and maximum error for width will be 0.477.It should be noted that MATLAB does not indicate the point where the maximum error occurs. But putting the values from input range into the regression equation it is found that maximum error occurs for the extreme values of outputs. For example consider the regression equations for GSM and Width at 5%X5% shrinkage target in 20 Gauge machines. 134 Now error (deviation) = 63.8-63.32 = 0.48 (Maximum value) [most accurately 0.4705≈0.470: see APPENDIX-A] = 0.75 % only 8.4 Application of WINQSB WINQSB is an another advanced mathematical software. It gives a detailed Regression summary with analysis of variance. Regression equation can also be found directly from here. A typical example has been shown in table (xiii) GSM = 522.26 - 7.57 Y.C. – 55.73 S.L∙ ∙ ∙ ∙ ∙ ∙ ∙ (1) Width = 30.398 - 0.507 Y.C. +13.521 S.L ∙ ∙ ∙ ∙ (2) When yarn count (Y.C.) is minimum, i.e. 18 and stitch length is minimum, i.e. 2.47 STARFISH gives GSM = 258 (maximu m value) Equation (1) gives GSM = 522.26 - 7.57 X 18 – 55.73 X 2.47 = 248.35 (maximu m value) Now error (deviation) = 258-248.35= 9.65 (Maximum value) [most accurately 9.7286 ≈9.73: see APPENDIX-A]=3.74 % only Again when yarn count (Y.C.) is minimum, i.e. 18 and stitch length (S.L.) is maximum, i.e. 3.11 STARFISH gives Width = 63.8 (maximu m value) Equation (2) gives Width = 30.398 - 0.507 X 18 + 13.521 X 3.11= 63.32 (maximu m value) 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 135 T ABLE XVIII AN EXAMP LE OF WINQSB GENERATED REGRESSION RESULTS Knitting Machine Type : 18G 30"D 1728N Target : L.S.Х W.S.=2.7% Х 6.3% Y.C. 14 14 14 14 14 16 16 16 16 16 18 18 18 18 18 20 20 20 20 20 22 22 22 22 22 S.L. 2.78 2.96 3.14 3.32 3.38 2.78 2.96 3.14 3.32 3.38 2.78 2.96 3.14 3.32 3.38 2.78 2.96 3.14 3.32 3.38 2.78 2.96 3.14 3.32 3.38 GSM 297 282 269 257 250 263 250 239 228 222 237 225 215 205 200 216 205 196 187 182 198 188 180 172 167 WIDTH 55.6 58.2 60.7 63.1 64.2 54.4 56.9 59.2 61.5 62.6 53.3 55.6 57.9 60.1 61.1 52.2 54.5 56.6 58.7 59.7 51.2 53.4 55.5 57.5 58.5 Regression Summary - GSM Mean Variable Standard Name Deviation GSM 221.2 35.42598 Constant Y.C. 18 2.886751 S.L. 3.116 0.2278157 Se=4.895592 R-square = 0.9824944 Regression Coefficient Standard Error 613.1526 -11.16 -61.31984 R-adjusted = 15.05345 0.3461706 4.386477 0.9809029 Analysis of Variance (ANOVA) -GSM Source of Degree of Sum of Mean Variability Freedom Square Square Regression 2 29592.73 14796.37 Error 22 527.2701 23.96682 Total 24 30120 Reg. Eq. (GSM) : 613.1526 - 11.16 Y.C. - 61.31984 S.L. Variable Name WIDTH Constant Y.C. S.L. Mean 57.688 18 3.116 Standard Regression Deviation Coefficient 3.484408 29.03919 2.886751 -0.6429999 0.2278157 12.90847 Standard Error 0.7011116 1.61E-02 0.2042993 Se =0.2280113 R-square = 0.9960747 R-adjusted = 0.9957179 Source of Variability Regression Error Total Analysis of Variance (ANOVA) - Width Degree of Sum of Mean Freedom Square Square 2 290.2426 145.1213 22 1.143761 5.20E-02 24 291.3863 Reg. Eq. (Width) :29.03919-0.6429999Y.C.+12.90847 S.L. 8.5 EXPLORING MEANS OF WINQSB RESULTS 1) Regression equation gives a forecasted output value of GSM or Width for a target shrinkage. 2) The coefficient of variation “ R-Square ” value is a “goodness of fit” measure. R2 is defined as: R2 =SSR/SST Where SSR= Regression sum of squares SST= Total sum of squares SSE= Sum of square error. It ranges in value from 0 to 1. In our case, R2 is giving a measure of the amount of reduction in the variability of GSM or Width obtained by using the regressor variables yarn count and stitch length in the model . For example, R2 =0.9960747 (from Regression Summary – GSM of shown in the table (xiii) 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 3) meaning approximately 99.61% of the variation in the GSM values can be explained by using the mentioned two explanatory variables. However a large value of R2 does not necessarily imply that the regression model is a good one. Adding a variable to the model will always increase R2 meaning the SSR has increased. In order to keep from over massaging the data,an eye must be kept on the adjusted R2 statistic as the more reliable indication of the true goodness of fit because it compensates for the reduction in the SSE due to the addition of more independent variables. Thus it may report a decreased adjusted R2 value even though R2 has increased, unless the improvement in SSR is more than compensated for by the addition of the new independent variables. In fact, if unnecessary terms are added, the value of R2 adj will often decrease. For example consider the GSM regression model of the table(xiii). The adjusted R2 for the model (R2 adj =0.9957179) is very close to the ordinary R2 (R2 =0.9960407)indicating a true goodness of fit. When R2 and R2 adj differ dramatically there is a good chance that non-significant terms have been included in the model. Standard Error (Se) represents the amount of scatter in the actual data around the regression line and is very similar in concept to the SSE . Once we have Se value, we can take advantage of a rough thumb rule that is based on the normal distribution and states that we have 68% confidence the actual value of GSM or Width would be within +/-1 Se of our predictable value. Likewise we have 95% confidence that the actual value of GSM or Width would be within +/- 2 Se of our predicted value. As from the example of table (xiii) of section 8.4, the predicted value for Width (when yarn count is18 and stitch length is 2.78) is : 29.03919-0.6429999X 18+12.90847 X 2.78 or 53.35 [by putting input values in reg. equation : (Width) =29.039190.6429999Y.C.+12.90847 S.L] Our 68% confidence interval would be [53.35 – 1(0.23); 53.35+1(0.23)] or [53.12, 53.58] Our 95% confidence interval would be [53.35 – 2(0.23); 53.35+2(0.23)] or [52.89, 53.81] 136 9. DETERM INATION OF ERROR RANGE FOR CUSTOM IZATION OF STARFISH 9.1 STARFISH GUIDELINE AND ITS APPLICABILITY It has been already mentioned earlier that STARFISH model prediction equations have been developed from many industrial trials and represent average values for typical wet processing routes from the actual values for yarn count and stitch length which the operator has chosen to enter. So calibration is required to give predictions which apply directly to own industrial situation. STARFISH prediction model provides calibration routines which allow to modify the predictions which STARFISH makes by establishing calibration factor through increasing or decreasing courses and wales per unit found in the reference state. But it is too much experimental and consumes significant resources for monitoring no. of courses and wales found practically in the reference state. So to follow STARFISH guideline a sufficient number of new developments have to be made which will then be subjected to deep examination for reliable estimates of reference courses and Wales. Though it will give the most accurate calibration but factory people generally don’t observe or keep recods of such parameters. They are also generally not interested to work with such outputs which are not major concern of most buyers.. So it will be a better approach if STARFISH customization is done by determining error range from available practical outputs with that of STARFISH outputs. Such customization will also be easily understood and welcomed by most knitters. 9.2 COMPARISON OF STARFISH PREDICTION WITH PRACTICAL RESULTS Tables (xiv)-(xvii) show the deviations between STARFISH predictions and practical outputs for similar values of target shrinkage(obtained from section 7.3 ). Based on such statistical measures calibration can be done according to knit machine (gauge) wise. 8.6 REMARK ON THE APPLICATION OF MATLAB AND WINQSB It is now clear that a multiple regression model satisfactorily supports the STARFISH prediction system. If we calculate the R2 and R2 adj for each individual trial then it may be found that the values lie within the range 0.97-0.99 both for GSM and Width. Once the outputs from the practical range of inputs for a particular target from the software are obtained, then regression equation can be established so that it can be used confidently for prediction of outputs without the use of computer. This may save time and help taking instant decision while the knitter is outside his normal desk. Also these equations may provide valuable support to other knitters which are still out of the reach of such technology. 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 138 T ABLE XIV DETERMINING CALIBRATION FOR ST ARFISH P REDICTION FOR KNITTING MACHINE TYP E : 18 GAUGE , 30 INCH DIA ., 1728 NEEDLES (18G 30”D 1728N) GSM Obs.No. STARFI SH (Original ) Predictio n 1 240 2 232 3 216 4 213 5 196 6 200 7 199 8 213 Practica AE l (Factory ) 272 231 231 222 195 205 202 217 32 1 15 9 1 5 3 4 WIDTH MA APE MAP STARFI E E SH (Original ) Predictio n 13.3 61 0.4 60 6.9 58.8 4.2 60.6 8.75 0.5 3.88 57.1 2.5 54.4 1.5 55.8 1.88 52.5 Practical AE MA APE (Factory) E MAP E 56 59.5 56 58 54 53 54.5 51 3.91 5 0.5 2.8 2.6 3.1 1.4 1.3 1.5 8.2 0.83 4.77 4.29 2.27 5.43 2.57 2.33 2.86 AE = Absolute Error MAE = Mean Absolute Error APE = Absolute Percentage Error MAPE = Mean Absolute Percentage Error MAE=5.43 and MAPE=2.54. calibration is +/-5.43 or +/-2.54% So revised STARFISH Discussion of the results: ● While achieving target shrinkage by existing 18G machines, STARFISH (original) calibration should be considered as +/2.27 or +/-3.91% ●Ignoring factory results for data no.1 we get revised MAE=1.88 and MAPE=3.3%. So revised STARFISH calibration is +/-1.88 or +/-3. For Width For GSM ● While achieving target shrinkage by existing 18G machines, STARFISH calibration should be considered as +/-8.75 or +/3.88% ●Ignoring factory results for data no.1 (which is quite unexpected and may be due to some catastrophic situations or improper process monitoring ) we get revised T ABLE XV DETERMINING CALIBRATION FOR ST ARFISH P REDICTION FOR KNITTING MACHINE TYP E : 20G GAUGE , 30 INCH DIA ., 1944 NEEDLES (20G 30”D 1944N) GSM Obs.No. STARFI SH (Original ) Predictio n 1 210 2 213 3 204 4 200 5 209 6 195 Practica AE l (Factory ) 217 216 200 190 209 200 7 3 4 10 0 5 WIDTH MA APE MAP STARFI E E SH (Original ) Predictio n 3.33 58.6 1.41 58.1 1.96 60.1 5 61.1 4.83 0 2.38 60.4 2.56 57.1 Discussion of the results: For GSM ● While achieving target shrinkage by existing 20G machines, STARFISH calibration should be considered as +/-4.83 or +/2.38% Practical AE MA APE (Factory) E 58 56 58 60 57.5 56 0.6 2.1 2.1 1.1 2.9 1.1 1.02 3.61 3.49 1.80 1.65 4.8 1.93 MAP E 2.77 For Width ● While achieving target shrinkage by existing 28G machines, STARFISH calibration should be considered as +/-1.65 or +/2.77% 117801-6464 IJET-IJENS © February 2011 IJENS I JE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 138 T ABLE XVI DETERMINING CALIBRATION FOR ST ARFISH P REDICTION FOR KNITTING MACHINE TYP E : 24 GAUGE , 30 INCH DIA ., 2256 NEEDLES (24G 30”D 2256N) GSM Obs.No. STARFI SH (Original ) Predictio n 1 205 2 203 3 185 4 207 5 173 6 183 7 161 8 177 Practica AE l (Factory ) 207 202 198 218 198 174 157 177.5 2 1 13 11 25 9 4 0.5 WIDTH MA APE MAP STARFI E E SH (Original ) Predictio n 0.97 69.1 0.49 70.1 7.03 74.6 5.31 70.8 8.19 14.45 4.49 72.9 4.91 66.4 2.48 70.8 0.28 61.4 Practical AE MA APE (Factory) E MAP E 64 64 69 67 69.5 64.5 70.5 61 4.69 5.1 6.1 5.6 3.8 3.4 1.9 0.3 0.4 7.38 8.7 7.51 5.37 3.32 4.66 2.86 0.42 0.65 Discussion of the results: For GSM ● While achieving target shrinkage by existing 24G machines, STARFISH calibration should be considered as +/-8.19 or +/4.49 % ●Ignoring factory results for data no.5 (which is quite unexpected and may be due to some catastrophic situations or improper process monitoring ) we get revised MAE=5.78 and MAPE=3.07. So revised STARFISH calibration is +/-5.78 or +/- 3.07 % For Width ● While achieving target shrinkage by existing 24G machines, STARFISH calibration should be considered as +/-3.32 or +/4.69% ●Ignoring factory results for data no.5 we get revised MAE=3.31 and MAPE=4.69. So revised STARFISH calibration is +/- 3.31 or +/- 4.69% T ABLE XVII DETERMINING CALIBRATION FOR ST ARFISH P REDICTION FOR KNITTING MACHINE TYP E : 28 GAUGE , 30 INCH DIA ., 2640 NEEDLES (28G 30”D 2640N) GSM Obs.No. STARFI SH (Original ) Predictio n 1 179 2 151 3 145 4 121 5 119 Practica AE l (Factory ) 180 146 144 120 129 1 5 1 1 10 WIDTH MA APE MAP STARFI E E SH (Original ) Predictio n 0.59 70.9 3.31 71.3 0.69 75.1 3.6 0.82 2.76 74.7 8.4 63.8 Discussion of the results: For GSM ● While achieving target shrinkage by existing 28G machines, STARFISH calibration should be considered as +/-3.6 or +/2.76% Practical AE MA APE (Factory) E 69 68 73.5 72 63 1.9 3.3 1.6 2.7 0.8 2.68 4.63 2.13 2.06 3.61 1.25 MAP E 2.86 For Width ● While achieving target shrinkage by existing 28G machines, STARFISH calibration should be considered as +/-2.06 or +/2.86% 117801-6464 IJET-IJENS © February 2011 IJENS IJE NS International Journal of Engineering & Technology IJET-IJENS Vol: 11 No: 01 10. A PPLYING CALIBRATION PRACTICALLY: A CHIEVING TARGET SHRINKAGES Now the question arises-how one should compare the practical outputs with STARFISH as it is impossible to guess before production what shrinkage value will be obtained from the finished product. The answer lies on the mathematical definition of shrinkage. It is well known that GSM, width and shrinkages are dependent on knitting variables. One cannot alter them without changing knitting variables but conditional adjustments could be made with the help of finishing technology. For example, if a finished fabric sample has a length of 200 cm and width of 100 cm showing shrinkage 7% Х 2% then one can say that fabric sample will show 5%Х5% shrinkage if length and width are adjusted to (200-200X 0.07)X (100/95) and (100-100X 0.02)X (100/95) i.e. 195.79 cm and 103.16 cm. As consumers and so customers always take shrinkage as the most rigid issue one has to adjust th e shrinkage level to customer's standard (e.g.5%Х5% for Plain Jersey) before predicting through calibrated STARFISH. In this way one can also avoid storing so many regression equations for GSM and width keeping the most preferred ones. 11. CONCLUSION OF THE W ORK The results of analysis obtained from this thesis work are: 1. STARFISH prediction system can be explained through a multiple regression model very satisfactorily. The values of R2 and R2 adj found through the regression analysis lie above 0.95 both for GSM and Width. This means that the regression models can be used as a substitute of this software very effectively for any type (gauge) of knitting machine. 2. As STARFISH predictions may not coincide with a particular factory result, some standard statistical measures like MAE , MAPE may be adopted to determine the error range as a part of STARFISH customization .During this project thesis MAE and MAPE for each gauge machine of Beximco Knitting Limited were calculated and the findings are summarized below. i) While using 18G machines , MAPE for STARFISH would lie within 2.5% in case of GSM and within 3.3% in case of width ii) While using 20G machines , MAPE for STARFISH would lie within 2.4% in case of GSM and within 2.8% in case of width . iii) While using 24G machines , MAPE for STARFISH would lie within 3.1% in case of GSM and within 4.7% in case of width . iv) While using 28G machines, MAPE for STARFISH would lie within 2.8 % in case of GSM and within 2.9% in case of width. 12. END W ORDS Although cotton-knit fabrics have been manufactured for decades, prediction of GSM, width and shrinkage is still regarded as the most widespread and difficult problem with the performance of such fabrics. In fact, very few people in the industry know how to calculate the weight, width and 139 shrinkage after dyeing and finishing of a given quality of knitted fabric before it has ever been manufactured. The resu lt is that, all over the world, product development of cotton knits is carried out on a “ trial and error” basis followed by adjustment and re-adjustment during successive batches of bulk production. By customization of STARFISH Technology, the factory management of a knit plant can save a great deal of time and money by answering many questions and eliminating unworkable ideas before financial, physical and human resources are committed. As shown in this work, the production management of Beximco Knitting Limited now can predict satisfactorily about its factory outputs with the help of calibrated STARFISH results. Though the calibration was done only for Plain Jersey fabric of medium deep shade but the calibration procedure is similar for all types of cottonknitted fabric of every shade. Again the regression model of STARFISH software, developed in this work, would be a fantastic tool for a knit-manufacturer as he can consult it confidently outside of the computer desk. Though calibration task involved in this work was based on limited data, the factory management can utilize the software to find what GSM and width will be derived from a typical knitting machine for a particular dyed fabric. The predictions would be more accurate if the management generates more STARFISH recommended data for upgrading calibrations. As the last words it must be remembered that STARFISH does not remove the need for production of a sample prior to full-scale manufacturing. So it is necessary to make a trial piece or two and have them processed. One needs to make sure that they conform to what is expected by taking measurements. Then he should get the customer to approve the samples, examining both performance and aesthetics. Also during full-scale production, samples from the bulk should be tested. The customer is demanding for a particular output and the manufacturer can not go without submitting practically what the customer wants. A CKNOWLEDGM ENTS The present work was supported by Beximco Knitting Limited.The authors would like to thank the employees of Beximco Knitting Limited for their co-operative hands. 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