When two pieces of fabric are joined by stitching them together, it creates what is known as a seam. There are many different types of seam from the basic plain seam to the fancy French seam.
Seam engineering, the determination of the best stitch type, seam configuration, and thread type which should be used for a particular assembly, requires a thorough knowledge of many variables. The improper selection of any one component can result in failure of the sewn junction, and ultimately failure of the product manufactured.
The characteristics of a properly constructed sewn seam are strength, elasticity, durability, security, and appearance. These characteristics must be balanced with the properties of the material to be joined to form the optimum sewn seam. The end use of the item will govern the relative importance of these characteristics. The selection of the seam type and stitch type should be based upon these considerations.
The seam efficiency of the sewn seam should be as high as possible. This will produce sewn seam strength with a balanced construction that will withstand the forces encountered in the use of the sewn item.
The elasticity of a sewn seam should be slightly greater than that of the material which it joins. This will enable the material to support its share of the forces encountered for the intended end use of the sewn item.
The durability of a sewn seam depends largely upon its strength relative to the elasticity of the seam and the elasticity of the material. However, in less elastic, tightly woven or dense materials, there is a tendency for the plies to “work” or slide on each other. To form a durable sewn seam in these types of fabrics, the thread size must be carefully chosen. The stitch density also needs to be carefully determined for the material so as not to cause excess tension which will unbalance the elasticity and cause puckering. It is also important to minimize abrasion and wear by contact with outside agencies to promote durability.
The security of a sewn seam depends chiefly upon the stitch type, spi, and its susceptibility to become unraveled. The stitch must be well set to the material to prevent snagging that can cause rupture of the thread and unraveling of certain stitch types.
The appearance of a sewn seam generally is governed by the proper relationship between the size and type of thread, the stitch density, and the texture and weight of the fabric.
In addition to these general characteristics, the technique and skill of the sewing machine operators also govern the appearance of the sewn seams.
Seam Type SS (Superimposed)
General Seaming
751a Number: SSa
ISO 4916 Number: 1.01
Common Application: Most common seam construction for both wovens & knits.
Requirements:
1) Seam Margin must be specified to maintain fit.
2) A
seaming guide or trimmer is used to keep the edges even.
Seam with Piping
751a Number: SSk
ISO 4916 Number: 1.12
Common Application: For seam apparel, furniture with piping in seam
Requirements:
1) Seam Margin must be specified to maintain fit.
2) A seaming guide is used to keep the edges even.
3) May require a Foot with grooved bottom if cord is used in piping.
Attaching Elastic
751a Number: SSt
ISO 4916 Number: 7.09
Common Application: For seaming knitted or woven elastic to Boxers, Gym Shorts
Requirements:
1) Specify Width of Elastic;
2) Usually 2, 3, or 4 rows of 401 chainstitch are used to make this seam - Specify Needle Spacing. (Ex.: 1 1/4" Elastic with 4 rows 1/4" needle spacing)
Seaming & Taping
751a Number: SSab
ISO 4916 Number: -
Common Application: Joining Shoulders with Stay Tape; Attaching Facing to Jacket Front with Stay Tape
Requirements:
1) Specify width of Stay Tape;
2) Specify Seam Margin
Finishing belt ends
751a Number: SSb
ISO 4916 Number: 1.04
Common Application: Not common; Attaching elastic to waistband
Requirements:
1) Seaming the plies with one or more rows of stitches.
Jeans waistbands ends
751a Number: SSc
ISO 4916 Number: 1.06.01
Common Application: Not common. SSe is more common.
Requirements:
-
Nice work.
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