A seam is the joint between the two parts of a garment. For the perfect fitting and look of the garment seam appearance and its strength has to be proper. Many factors like appropriate sewing, needle size and its type, fabrics used and its weight, stitches done on the garment, seam construction and tension level of thread influences the strength of seam.
Seam strength testing is basically an examination of the amount of pressure required to tear or break the seam of the garment. Measurement of seam strength is a part of quality control procedure which is essential for garments. The fabrics are tested for it in the machine that checks the point at which the seam breakage occurs. There are many problems associated with the seam strength if there is any fault during making of seam, for instance- the seam and fabric splits at same point of time and sometimes the seam is safe but the fabric tears off :-
Various criteria associated with appropriate seam implementation:
Stitch and seam construction
The best available option of stitch to ensure strong seams is Locked stitch as in this stitch there is interlocking of the threads which increases the seam strength. There are various types of seam constructions, the list is as follows:-
a) Decorative Seam As the name suggests this seam is done for decorating the garment. This is done on one or more than one layer of fabric through many rows of stitches sewn on them.
b) Super Imposed Seam Superimposing the seam is the simplest and widely used type of seam construction. The border of one piece is kept on another piece of fabric, then sewn together.
c) Applied Seam When some outside material other than the fabric itself like lace, patch, etc are sewn on the seam or edge of the garment, it is known as applied seam.
d) Bound Seam This seam is also used for decorative purpose. Here the edges are attached by means of tapes or through self binding.
e) Single Ply Construction Seam This seam is constructed from single layer or piece of fabric. Generally used for manufacturing belts and belts loops.
f) Edge Neatening Here the edges of the fabric are trimmed, hemmed and folded through stitches.
g) Lapped Seam This is the strongest type of seam usually used for denims. Here the seam is done on the fabrics overlapped.
There are many factors associated with sewing needle which are important from the viewpoint for better seam strength and appearance. The diameter of the needle, the shape of its tip and size of the eye h*** of the needle affects the seam construction of the garment. The size of the eye h*** of the needle should be in accordance with the thickness of the thread. If the needle h*** is smaller and does not provide effortless passing of the thread then there is the possibility of wearing out of the thread during use of the garment. And if the needle h*** is larger and the thread is finer than the level required, mis-stitch might result due to low quality of loop formation and thread control. Thus proper ratio of size and type of sewing needle and thread is required. Also to avoid harm to the fabric due to excessive heating of needles while stitching special needles have been developed like- titanium nitride coated needle.
Fabric type and weight
Seam strength and its performance also depends upon the various characteristics of fabrics used. The material of the fabric, the type of fabric weave, thread count, the pattern positioning, type of yarn and seam direction.
Thread type, construction, size and finish
The type of the thread used, its construction, size and finishing influences the seam strength of the garment. There are many types of threads like cotton thread, polyester thread, silk threads, etc. It is a known thing that polyester thread is more durable than cotton thread. However the type of thread used depends upon the fabrics being used, for eg.- for silk fabrics silk thread is used.
There are different types of thread construction like multi-filament, core, spun, textured, etc. Continuous filament core threads provide better seam strength compared to other construction of threads. Different thread sizes are available in market but finest thread are preferred more as longer length of finer threads can be wind around the lock-stitch machine and they do not acquire much space in the seam. This avoids seam puckering.
Sewing thread's elasticity should match to the elasticity of the fabric used. Also the whole length of the thread should have equal elasticity level throughout its reel which ensures proper stitches. If it is not proper then it could result into tearing of fabric or thread breakage of the garment. Different fabrics require threads of different elasticity, for instance threads used for knitted, synthetic or woven fabrics are different.
Thread tension or Stitch balance
The sewing machine tension should be well adjusted in order to get good stitch. In case of loose thread tension while stitching, it would result into lower seam strength, and if thread tension is high then it might lead to puckering. It is advisable to set medium level of thread tension in sewing machines. Also the parts of the sewing machine should be well oiled and smooth enough to ensure lower loss of thread, smooth and flawless stitching or damage to the thread used.
Hence from the above mentioned factors essential if are put into consideration while manufacturing of seam of the garments, it would surely result into flawless garment production and better seam presentation and durability. For export houses these points are to be taken care of. The trick is to use matching needle type and size, thread finish, type, size and construction, type of seam construction and adjusting appropriate thread tension in accordance with the fabric type and weight also the method of stitching being used.
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