F.B.N. Ferreira, S.C. Harlock and P. Grosberg
A study of thread tensions on a lockstitch sewing machine was made, measuring simultaneously both the needle and bobbin thread tensions. Experiments were carried out under…
Abstract
A study of thread tensions on a lockstitch sewing machine was made, measuring simultaneously both the needle and bobbin thread tensions. Experiments were carried out under specified sewing conditions, whereby needle and bobbin thread tensioner adjustment, sewing speed, number of plies, fabric quality and sewing thread quality were varied in order to investigate the effect of these factors on the needle and bobbin thread tensions. The patterns of the thread tension traces obtained were analysed as well as the effect of these factors on the peak tensions detected on both thread tension traces. Four significant peak tensions on the needle thread tension trace and two significant peak tensions on the bobbin thread tension trace were detected, during a stitch cycle. It was found that no significant variations occurred as far as the timing and shape of the peak tensions were concerned. However, variations were detected in the peak tensions according to the sewing conditions, as expected. From the analysis of the data obtained, multiple regression equations were derived to predict, with a good degree of accuracy, the peak tensions generated, according to the sewing conditions.
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F.B.N. Ferreira, S.C. Harlock and P. Grosberg
A study of thread tensions on a lockstitch sewing machine was made, measuring simultaneously both the needle and bobbin thread tensions. Investigates the relationship between the…
Abstract
A study of thread tensions on a lockstitch sewing machine was made, measuring simultaneously both the needle and bobbin thread tensions. Investigates the relationship between the peak tensions generated during the experiments and the corresponding seam balance. It was found that under the conditions of the experiments it is possible to define an envelope of conditions under which balanced seams will be obtained.
Md Vaseem Chavhan and Mandapati Ramesh Naidu
This paper aims to develop at sewing thread during the seam formation may lead to the compression of fabric under seam. In the present study, the model has been proposed to…
Abstract
Purpose
This paper aims to develop at sewing thread during the seam formation may lead to the compression of fabric under seam. In the present study, the model has been proposed to predict the seam compression and calculation of seam boldness, as well as thread consumption by considering seam compression.
Design/methodology/approach
The effect of sewing parameters on the fabric compression at the seam (Cf) for fabrics of varying bulk density was studied by the Taguchi method and also the multilinear regression equation is obtained to predict seam compression by considering these parameters. The framework has been set as per the single view metrology approach to measuring structural seam boldness (Bs). One of the basic geometrical models (Ghosh and Chavhan, 2014) for the prediction of thread consumption at lock stitch has been modified by considering fabric compression at the seam (Cf).
Findings
The multilinear regression model has been proposed which can predict the compression under seam using easily measurable fabric parameters and stitch density. The seam boldness is successfully calculated quantitatively using the proposed formula with a good correlation with the seam boldness rated subjectively. The thread consumption estimation from the proposed approach was found to be more accurate.
Originality/value
The compression under seam is found out using easily measurable parameters; fabric thickness, fabric weight and stitch density from the proposed model. The attempt has been made to calculate seam boldness quantitatively and the new approach to find out thread consumption by considering the seam compression has been proposed.
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F.B.N. Ferreira, S.C. Harlock and P. Grosberg
The purpose of this investigation was to try to develop a theoretical model to satisfy and explain the interaction between the needle and bobbin threads, the tensions developed…
Abstract
The purpose of this investigation was to try to develop a theoretical model to satisfy and explain the interaction between the needle and bobbin threads, the tensions developed and their influence on seam balance. An explanation of the conditions determining seam balance is proposed based on a “robbing back” theory of stitch formation.
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Md Vaseem Chavhan, M. Ramesh Naidu and Hayavadana Jamakhandi
This paper aims to propose the artificial neural network (ANN) and regression models for the estimation of the thread consumption at multilayered seam assembly stitched with lock…
Abstract
Purpose
This paper aims to propose the artificial neural network (ANN) and regression models for the estimation of the thread consumption at multilayered seam assembly stitched with lock stitch 301.
Design/methodology/approach
In the present study, the generalized regression and neural network models are developed by considering the fabric types: woven, nonwoven and multilayer combination thereof, with basic sewing parameters: sewing thread linear density, stitch density, needle count and fabric assembly thickness. The network with feed-forward backpropagation is considered to build the ANN, and the training function trainlm of MATLAB software is used to adjust weight and basic values according to the optimization of Levenberg Marquardt. The performance of networks measured in terms of the mean squared error and the layer output is set according to the sigmoid transfer function.
Findings
The proposed ANN and regression model are able to predict the thread consumption with more accuracy for multilayered seam assembly. The predictability of thread consumption from available geometrical models, regression models and industrial empirical techniques are compared with proposed linear regression, quadratic regression and neural network models. The proposed quadratic regression model showed a good correlation with practical thread consumption value and more accuracy in prediction with an overall 4.3% error, as compared to other techniques for given multilayer substrates. Further, the developed ANN network showed good accuracy in the prediction of thread consumption.
Originality/value
The estimation of thread consumed while stitching is the prerequisite of the garment industry for inventory management especially with the introduction of the costly high-performance sewing thread. In practice, different types of fabrics are stitched at multilayer combinations at different locations of the stitched product. The ANN and regression models are developed for multilayered seam assembly of woven and nonwoven fabric blend composition for better prediction of thread consumption.
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Darja Žunič‐Lojen and Jelka Geršak
The perfect interlacing of needle and bobbin thread in the stitch formation process and seam appearance depends first of all on correct pre‐tension of the tension regulator…
Abstract
The perfect interlacing of needle and bobbin thread in the stitch formation process and seam appearance depends first of all on correct pre‐tension of the tension regulator. Changes in the pre‐tension settings also have a direct influence on the tensile force during the sewing process. This contribution presents the influence of pre‐tension in a defined area on the tensile force in important phases of the stitch formation process. In addition the influence of the stitch velocity on tensile force was investigated. On the basis of statistic analysis it was ascertained in which pre‐tension area and stitch velocity the significant differences between tensile forces occurred.
Reyhaneh Shekarian, Sayyed Mahdi Hejazi and Mohammad Sheikhzadeh
Knitted fabrics have been widely used in a wide range of applications such as apparel industry. Since these fabrics are continuously subjected to the long-term tensile stresses or…
Abstract
Purpose
Knitted fabrics have been widely used in a wide range of applications such as apparel industry. Since these fabrics are continuously subjected to the long-term tensile stresses or tensile creep in real conditions, investigation of viscoelastic behavior of sewn knitted fabrics would be important especially at the seamed area. The paper aims to discuss this issue.
Design/methodology/approach
A lockstitch machine was used to produce sewn samples by knitted fabric. Factors such as stitch per inch (SPI), thread tension and thread type were variables of the model. Tensile creep tests under constant load of 200 N were conducted, and creep compliance parameter D(t) of samples was obtained as a response variable. A successive residual method (SRM) was also used to characterize viscoelastic properties of sewn-seamed fabrics.
Findings
The instantaneous elastic responses of the seamed samples were less than those of the neat fabric (fabric with no seam). An increase in sewing thread strength increases the instantaneous elastic response of the sample. SPI and thread tension have an optimum value to increase E0. High tenacity polyester thread, due to its higher elastic modulus, caused a larger E0 than polyester/cotton thread in sewn knitted fabric. Characteristics of seam including sewing thread type, SPI and sewing tension have significant influence on T0. Sewn-seamed fabric by high modulus thread shows less viscous strain T0 than the neat fabric (fabric with no seam). Viscous strain T0 decreases as SPI changes from 8 to 4 and/or 12. SPI and thread tension have an optimum value to increase the viscous strain T0. E1 is the same for optimum seamed fabric and fabric sample but T1 is about two times greater for seamed fabric. Retarded time for creep recovery increases by sewing process but characteristics of seam have significant influence on E1 and T1. All sewn knitted fabric samples used in this study could be described by Burger’s model, which is a Maxwell model paralleled with a Kelvin one.
Originality/value
This paper is going to use a different method named successive residuals to model the creep behavior of seamed knitted fabric. On the whole, this paper paved a way to obtain viscoelastic constants of sewn-seamed knitted fabrics based on different sewing parameters such as the modulus of elasticity of the sewing thread, SPI and sewing thread tension.
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Use of programme package ADAMS to simulate the sewing machine mechanisms is presented within this contribution. The simulation of needle bar mechanism was carried out. The…
Abstract
Use of programme package ADAMS to simulate the sewing machine mechanisms is presented within this contribution. The simulation of needle bar mechanism was carried out. The influence of velocity changes of the main shaft on velocities and acceleration of sewing needle in the penetration area is described on the basis of simulation results. Achieved data could be used for calculation of needle penetration force. The influence of length modification of needle bar mechanism elements on sewing needle velocity and acceleration is also presented. This analysis could contribute to better understanding of sewing machine activity.
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The chapter suggests two methodologies to measure inequality of opportunity in health in Israel, an ex-ante and an ex-post approach. In both cases, following the strategy recently…
Abstract
The chapter suggests two methodologies to measure inequality of opportunity in health in Israel, an ex-ante and an ex-post approach. In both cases, following the strategy recently suggested by Trannoy, Tubeuf, Jusot, and Devaux (2010), the chapter starts by introducing the production function of health, taking into account circumstances (the father’s years of education, his country of birth, the religion of the individual, his or her country of birth, age and gender) as well as effort variables (the level of education of the individual, his or her occupation and a variable describing his or her smoking habits).
The chapter also suggests then a decomposition of the overall health inequality into a legitimate and an illegitimate component, using the mean logarithmic deviation as inequality index, such a breakdown being applied to both the ex-ante and the ex-post approaches to equality of opportunity.