Definition of Seam:
A seam joins more than one piece of material together, and the various types of seams are used depends on the product to be sewn. Seams in clothing have different levels of complexity, depending on the design of the product. Seams in other sewn products have similar levels of complexity.
Some form of seam joining is used in virtually all product manufacture that involves the stitching of materials using sewing threads, and it is still by far the most important method used in the joining of textiles.
If we take into consideration the different requirements of a seam on the outside leg of a pair of jeans compared with a seam used in joining the perimeters of an air bag, there may be:
- More consistent stress loading of a seam on an air bag due to an even air pressure.
- An uneven pressure on a jean due to leg movements.
- Stress/pressure on a seam of an air bag due to rapid inflation of the bag.
- A gradual build-up of stress loading on the seam of the jean.
- A difference in the fabric ply angles, which could alter the strengths of the seams.
Accordingly, the angle of the ply means that it is the direction in which the fabric is cut.
There is one factor that both of these and other seams have in common; it is that the seams must combine the required standards of appearance and performance, while ensuring economy of production.
The aesthetic characteristics of a seam are usually influenced by the accuracy of the stitching, the visibility of threads of differing color to each other, and the surface of the fabric. Seam performance relates to the strength, extensibility, durability, security, and comfort and to the maintenance of specialist fabric properties.
Generally, the seam must exhibit similar properties to the fabric into which it is being introduced. In addition, depending on the physical properties of the area within a product, occasionally modify that product area.
The strength of a stitch line is assessed both longitudinally in the direction of the seam and transversely in perpendicular direction to the seam. It is assessed in terms of peak tensile load at break. The seam extensibility can be quantified simultaneously while applying the load longitudinally, and the seam grin can be measured while a seam is under transverse load.
Factors influencing the strength and extensibility of a stitch line seam include the following:
- Stitch density (stitches per centimeter)
- Thread tension (static thread tension setting on the sewing machine)
- Thread properties (strength and elasticity, determined by fiber type)
- Fabric integrity (cover or tightness factor)
The seam performance relates to the following:
- Strength
- Aesthetic appeal
- Extensibility
- Durability
- Ease of assembly
- Security
- Comfort in wear
The only British standard test in existence is the BS 3320:1998, “method for determination of slippage resistance of yarns in woven fabrics: seam method,” often referred to as the grab test. Seam strength is often referred to as seam efficiency, which is an expression of seam strength as a function of fabric strength.
………………………..Un-seamed Fabric Strength 100%
Seam Efficiency = ——————————————————
………………………………Seamed Fabric Strength
The requirements of seam extension can vary dramatically with the product application; Comfort stretch (up to 30%) for casual garments and performance wear and support garments can exhibit extensions of more than 100%—power stretch.
The durability and security of the seam are directly related to these properties and the integrity of the sewing thread under normal use and laundering conditions.
Many types of seams can be constructed in ways involving different raw materials, stitch types, and machinery. An optimum combination of these, along with minimized thread consumption, will provide an economical approach to manufacturing.
There are hundreds of different types of seams in sewing, so only the most common are discussed here. They are basically categorized into eight simple categories, which are described in the following subsections.
A seam should be suitable for the purpose for which it is intended, and the seam type depends on the product being sewn. The choice of seam must meet the required standards of appearance and performance, but it must also be economical if it is being used in a modern production environment, as cost can become an important factor. Thus when choosing a seam for a garment operation, the following factors should be considered:
- Aesthetic appeal
- Strength
- Durability
- Comfort in wear
- Ease of assembly
- Equipment availability
- Cost
Different Types of Seams in Sewing and Their Properties
Class 1: Superimposed Seams
Class 1 superimposed seams are generally two or more plies of fabric laid on top of each other, superimposed in the same orientation. They are stitched near the edge with one or more rows of stitching. The rows of stitching may be sewn simultaneously or consecutively. Superimposed seams (Figure 1) are the most basic and easiest to produce of all the seams types, and are frequently used in many areas of garment construction as well as for numerous other sewn products in the market.
Typical areas of a garment where superimposed seams are used are side seams on a pair of jeans, side seams on blouses or shirts and trousers, and for attaching zips and trims etc. The fabric edges would usually be overlocked in order to prevent the material from fraying. The seam is durable and is easy to produce, as it only involves one fabric placed upon top of another.
A disadvantage of this seam is that its strength is limited by the strength and types of sewing thread.
Class 2: Double-Lapped Seams
Double-lap seams (Figure 2) are among the strongest available and are used in many areas of sewn product manufacture where strength is required, particularly side seams on denim jeans, parachutes, tents and sports garments such judo suits.
In class 2 double-lapped seams:
- Two more plies are lapped together, overlaid, plain, or folded.
- These are secured with one or more rows of stitching.
- One of the most common is the double-lap felled seam, with two or more rows of stitching.
- This provides a strong seam with fabric edge protection.
- These are often used on the side seam of jeans, other denim products, and tents.
Class 3: Bound Seams
Bound seams (Figure 3) have many uses in apparel, such as hemming and binding operations for neatening fabric edges, and are also commonly used on luggage and inside tent joins.
Class 3 bound seams are formed by:
- Folding a binding strip around the raw fabric edge(s) and securing with one or more rows of stitching.
- This produces a secured neat seam on an edge often exposed to view or wear.
- These are often used on luggage.
Class 4: Flat Seams
This seam is also called a butt seam as the edges of the fabrics do not overlay one another, they will be butted together. Flat seams (Figure 4) are produced with a minimum of two plies of fabric, with the raw edges butted together and usually stitched using a cover-seam machine. These seams are most commonly used in knitted products, particularly underwear. A major advantage in this seam type is its reduced bulk.
Class 4 flat seams are:
- Produced with a minimum of two plies of fabric butted together at the raw edge on the same level.
- A minimum of two rows of stitching are introduced simultaneously, which are joined on one or both surfaces.
- These are often used in knitwear to reduce bulk around the join, especially in underwear.
Class 5: Decorative Seams
The decorative or ornamental stitch (Figure 5) is a series of stitches down a straight or curved line or following an ornamental design on a single fabric ply. A more intricate kind of stitch involves various systems of piping, producing an elevated line along the fabric surface. The stitching in a single fabric ply resulted in decorative effects on the fabric surface like pin tucks.
In class 5 decorative seams:
- One or more rows of stitching are introduced to one or more folded or plain plies of fabric.
- These are often used to create effects such as pin tucks and channel seams.
Class 6: Edge Finishing
Edge finishing / neatening stitch (Figure 6) could be seen where the edge of a single fabric ply is folded or covered with a stitch. The simplest of this process is known as ‘Serging’ where the raw edge of the fabric is secured by overedge stitching to prevent fraying of edges as well as edge neatening. This seam class involves seams whereby the edges are neatened by means of stitches and could be utilized in circumstances where the raw edge of fabric needs finishing.
In class 6 edge finishing:
- Line of stitches is formed at or over the edge of a plain or folded fabric ply(s).
- The simplest of these is serging, where the raw fabric edge is finished with a 500 class stitch.
Class 7: Edge Stitched Seam
Edge stitched seam involves seams that need the inclusion of another component at the edge of a fabric ply, for example, elastic braid inserted onto the edge of ladies briefs as shown in Figure 7. This kind of seam requires two components.
In class 7 Edge stitched seam:
- These seams are constructed with one piece of base material in a similar manner to lapped seams but include an added component, which is limited on both sides (a braided tape or a lace trim).
Class 8: Enclosed Seam
In this kind of seam class, only one piece of strip of fabric is turned on both edges. The general application of enclosed seams could be found in belt loops or belts for which a folder attachment can be done on the machine as shown in Figure 8.
In class 8 Enclosed Seam:
- These are classified as seams used on one ply of fabric, which is limited on both sides; this includes things such as belt loops.
Conclusion:
Seams play a crucial role in sewing, providing both functionality and aesthetics. Generally seams may be created with thread by hand or machine, or with fusion through chemical bonding. A seam is a method of joining two or more pieces of materials together by a row of stitching. Each type of seam offers unique benefits. Ready-made-garment seams have utility as well as aesthetic value, and certain characteristics are necessary for the seams such as strength, elasticity, durability, security and appearance.
References:
- Textile and Clothing Design Technology. (2017). In CRC Press eBooks. https://doi.org/10.1201/9781315156163
- Sinclair, R. (2015). Textiles and fashion : materials, design and technology. In Woodhead Publishing
- Karthik, T., Ganesan, P., & Gopalakrishnan, D. (2016). Apparel Manufacturing Technology. In CRC Press eBooks. https://doi.org/10.1201/9781315367507
- Garment Manufacturing Technology. (2015). In Elsevier eBooks. https://doi.org/10.1016/c2013-0-16494-x
