INVESTIGATION OF SEAM PUCKERING IN WOMAN’S BLOUSE

In this study, mechanical properties of the fabrics were investigated in order to fi nd the cause for seam puckering problem in armhole and neckline area of woman’s blouse. The same model of woman’s blouse was produced from two types of fabrics with diff erent raw material content: 100% silk and 100 % polyester. The obtained results show that both fabrics have a low shear rigidity, indicating that fabrics extension in bias direction is high. The fabrics extension in bias direction has infl uence on seam puckering in armhole and neckline area of the blouse because there is sewing in bias direction except sewing in warp and weft directions.


INTRODUCTION
The development of the apparel industry is conditioned by the successful management in terms of price and delivery on the one hand, and constant monitoring and meeting consumer demands in terms of quality on the other. Consumers evaluate the clothes quality through the comfort, aesthetic and functional properties of the clothes [1]. The seam is one of the basic ways of clothes assembling and as such, the quality of the seam is essential to the quality of clothes. The properties through which the quality of the seam is assessed are seam puckering, seam strength, seam slippage, uneven stitch density and other. In clothing manufacture, the seam puckering is a defect that occurs very often. Seam pucker is defi ned as [2] "a ridge, wrinkle or corrugation of the material or a number of small wrinkle running across and into one another, which appear in sewing together two pieces of fabric". Various factors have infl uence on seam puckering as the structural parameters of the fabrics, type of sewing machine, seam construction, as well as sewing parameters: feed mechanism, presser foot, stitch density, needle size and thread tension. During the clothing manufacture fabrics are exposed to various deformations like extension, compression, shear and bending that aff ect the aesthet-ic and functional quality of seams. Many researchers have investigated the infl uence of structural and mechanical properties of fabrics on seam puckering. Dobilaite and Petrauskas's [3] research has shown that shear rigidity, extension and fl exibility of the fabrics have an impact on the seam puckering. Stylious and Lloyd [4] also have investigated the infl uence of mechanical properties of fabrics on seam puckering and results show that shear and bending rigidity are the main factors which have infl uence on this defect. Carvalho, Demboski and Nofi toska [5] have investigated the relation between seam puckering, formability and tightness of fabric. The obtained results have shown that seam puckering increases when fabrics formability decreases.
In this study, mechanical properties of the fabrics were investigated to fi nd the reason for seam puckering in woman's blouse during the production process.

Materials
The same model of woman's blouse from two different fabrics was manufactured. In the both cases there were the seam puckering in neckline and armhole area. The model of woman's blouse is presented in Figure 1. The blouse is sleeveless with six pleats on the front neckline.  Table 1 are given. The surface density was measured according to the standard MKS BS EN 12127:1998, yarn count according to the standard ISO 7211-5:1984 and MKS EN 1049-2:2007 was used to determine yarn density. The blouse was sewn according to the parameters given in Table 2.  In Figure 2 and Figure 3 the seam puckering in the woman's blouse is presented for fabrics F1 and F2 respectively.

Methods
In order to fi nd the cause for seam puckering in neckline and armhole area, the mechanical properties of fabrics under small loads using FAST (Fabric Assurance by Simple Testing) system were investigated. The samples of fabrics were tested using compression meter (instrument FAST 1), bending meter (instrument FAST 2) and extension meter (instrument FAST 3) [6].
 Using the instrument FAST 1 the fabrics thickness was measured under loads of 2 g/cm 2 and 100 g/ cm 2 . The surface thickness of the fabrics was calculated as: Where:  Using the instrument FAST 2 the fabric bending length was measured. Bending rigidity was calculated using the equation: Where: B -bending rigidity (μNm) С -bending lenght (mm) Q -fabric sruface density (g/m 2 ).  Using the instrument FAST 3 the fabric extensibility under three diff erent loads (5 g/cm, 20 g/ cm and 100 g/cm) in warp and weft direction was measured. Extensibility of fabric under loads of 5 g/cm and 20 g/cm in combination with bending rigidity determines the fabric formability, according to the equation: The extensibility is also measured in bias direction under 5 g/cm load to determine fabric shear rigidity, using the equation: Where: G -fabric shear rigidity (N/m) EB 5 -extension under load of 5 g/cm.
In order to obtain consistent results, fabrics were conditioned overnight in standard atmosphere 20 ± 2 o C temperature and 65 ± 2% relative humidity before cutting. The fabrics sample cutting scheme in Figure 5 is presented.  Table 2 shows the obtained results for mechanical properties of the used fabrics. The formability values for both fabrics in weft direction are higher than 0.25 mm 2 . In warp direction, the fabric F1 has good formability, higher than 0.25 mm 2 , while the formability of the fabric F2 is 0 mm 2 . Formability values under 0.25 mm 2 create the possibility of fabrics producing seam puckering after sewing. The fabric F1 in both, warp and weft directions, and the fabric F2 in weft direction have extensibility values higher than upper control limit, which indicate that fabrics can easily stretched during cutting and sewing. In warp direction fabric F2, has extensibility values 0%, and this can lead to problems with overfeed seams. The fabric F1 in weft direction and fabric F2 in both warp and weft directions have bending rigidity below 5 μNm. Low values of bending rigidity mean that those fabrics potentially cause diffi culty during cutting and sewing. For shear rigidity, both fabrics have values less than 30 N/m. Low shear rigidity makes the fabric diffi cult to lay for cutting and these fabrics may require pinning down to avoid displacement of the cutting layer. According to the surface density both fabrics are lightweight fabrics. The control charts for fabric mechanical prop-erties, in Figure 6 and Figure 7 are shown for fabric F1 and F2, respectively.  During the sewing process, fabric is stretched along the stitch line as a result of transporting between feed dog and presser food. If the fabric has high extensibility then stretching during sewing will be high, which can be reason for seam puckering along the seam line after sewing. In the apparel industry, fabrics are usually sewn in the warp and weft direction. In the woman's blouse, except seams sewn parallel to the warp and weft yarns, there are seams witch deviates from warp and weft direction ( Figure  8). In the area of neckline, sewing start in warp direction, goes to bias direction, then in weft direction, again in bias and ends in warp direction. Similarly, the armhole seam, sewing start in weft direction, goes to a bias, continue in warp direction, again in bias direction and ends to a weft.

Figure 8: Sewing directions
In the analyzed models of woman's blouse, seam puckering in side seams (seam in warp direction) and shoulder seams (seam in weft direction) didn't occur. There wasn't seam puckering in weft direction because both fabrics have formability in control zone, 0.51 mm 2 and 1.11 mm 2 for fabric F1 and F2 respectively. In warp direction, fabric F1 has formability in the control zone 1.003 mm 2 and there wasn't seam puckering. Although, fabric F2 has formability in non-control zone in warp direction 0 mm 2 , there is no seam puckering because of the high bending rigidity in this direction (16,47 μNm). From Figure 2 and 3 it can be seen that puckering occurs in those seams which have deviation from the warp and weft direction of sewing, i.e. seam sewn in bias direction. The low shear rigidity values, 10.3N/m for fabric F1 and 13,4 N/m for fabric F2, indicate that fabric extension in bias direction is high. For fabric F1 extension in bias direction under 5 g/cm load is 11.9% and for fabric F2 is 9.2%. Although the FAST system doesn't set control limits for fabric extension in bias direction, low shear rigidity shows that the fabric extension is high. Based on the literature, the important property that aff ect the seam puckering is extensibility. Fabric with high extensibility is proneness to seam puckering.

CONCLUSION
During the manufacturing of woman's blouse, seam puckering was occurred in neckline and armhole area. In order to fi nd the reason for this problem, the mechanical properties of fabrics on FAST system were investigated. The obtained results have shown that the value for shear rigidity in both fabrics is low-er than 30 N/m. The low value of shear rigidity means that the fabric extension in bias direction (11.9% for fabric F1 and 9.2% for fabric F2) is high and that cause seam puckering.