A.sewing.needle is.a long slender.tool with.a pointed.tip. The.needle must.be able.to penetrate the material.being sewn, by.pushing the yarns.aside according to the.application,.without.damaging it. Modern needles.are manufactured from,high carbon steel.wire, nickel.or.gold plated. For.corrosion resistance 12.

Figure 2.6.1 sewing needle
Sewing.needle is the basic,element for sewing.fabric and garment. There are.two types.of sewing needle, one for hand.sewing and another for sewing.machine. The major difference between.the two is the location of the “eye”. The hand.needle has.the.eye at the back end.of the needle and.that needle pulls the thread.through.the fabric. The machine needle has the.eye at the front end and that needle pushes the thread.through the fabric 13.

2.6.2 Basic Features.of Sewing Needle:
The shank.is the.part of the needle that fits.into your sewing machine, with.the flat side to the back.The blade is.what.determines the needle size. (For example, a size needle.has a blade that is .75 mm in diameter.).The shaft is the “body” of the.needle, and the.groove that runs the length of the shaft holds the.needle thread.The point and.tip of the needle,refer to the size, shape and length all of which.vary based on the type of needle.The scarf of the needle,is an indentation on the backside that allows the.bobbin hook to smoothly grab the thread under.the sewing machine throat plate to create a proper stitch 14.

Figure 2.6.2 features of sewing needle

Ball.Points – Light.Ball Point is used.for sensitive fabrics such as knits, to prevent.damage to the loops. This is crucial for maintaining.the fabric’s elasticity. Medium ballpoint.and heavy ballpoint.are used for.fabrics containing.stretchable yarns. While sewing.the threads.are displaced not pierced. The needle pushes.between the fabric yarns rather.than “cutting rough” the yards 15.

• Ballpoint needles
Ballpoint needle.for heavier, looser sweater.knits, highly elastic fabrics, like
Spandex, or Lycra. 16.

There.are.two.needle sizing systems: American.and European. American needle.sizes.range from 8 to 19, and.European sizes.range.from 60 to 120. The larger.the.number, the larger the blade.of the needle. Often you will see.both sizing.numbers on the.needle package, such as 60/8.and 70/10 17.

Figure 2.6.4 Sewing Machine Needle Sizes
We are using dpx1 needle in our thesis work and needle size is 18.
• The American.system.uses 8 to 19, 8 being.a fine needle and 19 being.a thick heavy.needle.
• European sizes.range from.60 to 120, 60 being a fine needle.and 120 being a.thick heavy.needle 18.

The stitching process is the attachment.of different parts of the textile fabrics pieces. In this work place there are many operators.who perform single operation. All this factor decides what parts of textile fabric can be sewn.at that station21.

The stitching of denim jeans.is a labour intensive and complex process. Sewing machines used to process denim are.both interesting and complex 22.

• Stitching of inside seams
Joining the two pieces of textile.fabrics together face-to-face by sewing.through both
pieces, leaving a seam allowance.with raw edges inside the work. Machine stitching that
encloses the.raw edges.

• Stitching pocket hem
Stitching a hem on the.pocket opening, for example so that you first fold 1 cm to the.wrong
side and then again 2 cm, press.and stitch. The size.of the hem.can.vary a lot depending on
how the pocket.should look.

• Stitching zipper with J-stitch
A machine similar to the.pocket hem is used ,but this time topstitching.a zipper using a J-stitch .This operation is often semi-automated.and uses a programmable lock stitch sewing machine.to give a consistent shape because it is a highly visible section of the.garment.

• Stitching of side seams
Stitching the side.seams of the jeans together .The machine use for.his operaion also uses a tractor foot. This enables the machine to.climb excessive seam thicknesses where all the fabrics come.together in one join. It provides great.stability when clamping down on the fabric and reduces the possibility.of missed stitches.

• Bottom leg hems
In this operation the front.panel of denim jeans at the bottom side the hem is folded and stitched.

• Attaching waistband
Another important operation is attaching.the waistband to the main body of the jeans. The machine has two needles and the.waistband is fed through a continuous folder, thus reducing operator handling.

• Making belt loop
The fabric is folded through.a dedicated belt loop folder. The belt loops are fed through the.folder, producing a seam.

• Attaching belt loop
Belt loops on this garment are.attached using a semi-automatic belt looping machine. A continuous roll of finished.beltloop, is cut to length and a clamp holds the belt loop and presents it to the machine. Two needles are employed on this machine to sew.both ends of the belt loop in one operation. Again, operator handling is reduced where.only the body of the garment is held, making operation faster, more accurate and more efficient.

• Bar tacking for reinforcing
Exactly as for stitching the belt loop, this is a.similar machine but uses only one needle and is classified as a mechanised (fixed cycle) unit because when the treadle is pressed, the machine cycle cannot be interrupted until.the operation is finished.

• Pockets and labels
Semi automatic machines.require less human involvement and do more of the work autonomously .Such machines are used.to attach pockets and to attach labels to the jeans 22.

2.8.1 Seam efficiency
Seam efficiency mainly depends.upon the dimensional ; surface characteristics of the sewing thread, the tensile behavior of denim fabrics ; sewing thread and the.machine ; process parameters. It was reported previously be observed that with the increase.in Lycra percentage the seam efficiency increases. The increase in seam efficiency.with Lycra percentage is because of the higher elasticity and better compatibility.of the sewing thread with the denim, which subsequently increases the seam efficiency. This is in accordance with the.earlier result (i.e. The higher percentage of Lycra in the denim increases the fabric elasticity and.seam performance) obtained by Gurarda and Meric.

Seam efficiency is usually measured according to ASTM-D 1683 method on the.Instron tensile tester. Seam efficiency was calculated.as the percent seam strength over fabric strength by using the following formula 23.

Seamed fabric strength
—————————— X 100
Original fabric strength

We can use Seam efficiency.to measure the strength (durability) along the seam line. Durability is defined as necessary to satisfactory seam’s functional.performance, and efficient seams are assumed to be more durable.than weak ones.

22.Denim manufacturing, finishing and application
23. Gurarda A and Meric B, “Sewing needle penetration forces and elastanefibre
damage during the sewing of cotton/elastane woven fabrics”, Text Res J, 75 (8), 628-