Scope of Seam Engineering to Increase the Seam Strength by Controlling Different Parameters (Part-2)

Scope of Seam Engineering to Increase the Seam Strength by Controlling Different Parameters (Part-2)
Authors: MD. Momenur Rahman,
Kazi Mustafijur Rahman,
 
Rabeya Siddiqua
Atish Dipankar University of Science and Technology
Dhaka, Bangladesh

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Seam Strength Test
Seam strength is the strength of seam assembly in a garment. It is a function of the strength of the thread used for the seam, type of seam assembly in a garment and type of fabric used among other factors.

Determination of Seam Strength
In a lab CRE type tensile testing machines such as INSTRON is used before testing the samples are prepared. The method is called Grab Test.
  • If the specimens are from manufactured items such as garment then five specimens are cut having a length of 270 mm on either side of the stitch line and a width of 100 mm parallel to the stitch line. 
  • If the specimens are prepared from fabric then seam strength is measured in warp, weft and bias directions. In such cases swatches are cut in these three directions.
The effect of needle temperature on different size needle influence machine speed or SPM (Stitch per Minute). That effect the strength of seam.

Methodology

Considering Factors

Main
  • Seam class
  • GSM
  • Sewing thread
  • Stitch type (301 Lockstitch or 401 Chainstitch)
  • Thread size
  • Stitch Per Inch
  • Stitch Per Minute
Partial
  • breaking strength
  • breaking elongation
  • deformation energy.
Estimating Seam Strength
Below are two formulas that were developed for estimating the seam strength on woven fabrics.

To do the calculations, you need to know the following:
  • Stitch type (301 Lockstitch or 401 Chainstitch)
  • Thread Strength (Single-end breaking strength of the thread, measured in pounds)
  • Stitches per inch 
Determination of seam strength in Laboratory
(ASTM 1683-04 Standard Procedure)

Significance of the test
  • Determines the seam efficiency of a specified seam assembly with each fabric.
  • If a determination cannot be made as to which seam is the best suited for a particular fabric, all should be evaluated.
  • Used to determine either the sewn seam strength of textiles or the efficiency of a seam assembly with any given fabric.
  • Additionally, the seam strengths of different fabrics can be compared directly by using one of the standard seam assemblies specified because current information about laboratory precision is incomplete, comparative tests may be advisable.
Relevant field of test application
  • This test method is applicable whenever a determination of effective sewn seam strength, that is, the optimum seam interaction, is required.
  • The breaking force of the seam and fabric will permit determination of seam efficiency.
  • This test method can aid in determining optimum seam interaction for any given fabric by comparing the properties of the fabric with and without seams.
  • Seam engineering techniques for specific fabric types can also be determined by utilizing this test method.
Prospected use of the test
  • This test method can be used to determine when the sewn seam is affected by seam slippage.
  • While the ultimate consequence of this phenomenon is rupture, seam slippage greater than either the values stated in customer specifications, or as agreed upon by purchaser/supplier may severely reduce the integrity such that the product cannot be used for its intended purpose.
  • (An example of a commonly used seam slippage value is 6 ± 1 mm [0.25 ± 0.04 in.]). 
 
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