SPI Recommendations for Woven Garments

A list of garments and the typical number of Stitches per Inch recommended for each of them is given below:

WOVEN GARMENTS

Garments	SPI	Comments	Garments	SPI	Comments
Denim Jeans, Jackets, Skirts	7 – 8	Fewer stitches per inch Generally will give a more contrast stitch appearance.	Children’s wear	8 - 10	Usually 8 to 10 SPI is adequate to provide adequate seam strength and at the same time allow for quicker cycle Times.
Twill Pants or Shorts	8 – 10	More stitches per inch Will help minimize seam grinning.	Dresses, Skirts	10-12	Due to many of the operations being lockstitch, usually 10 – 12 SPI is required to provide adequate seam Strength.
Trousers, Dress Pants, Slacks	10-12	On some operations like serge panels, it may be desirable to use a longer stitch length.	Blind-stitch Operations on Slacks, Dresses Skirts, etc.	3-5	A long stitch length is desirable to minimize the dimple or appearance of the needle penetration on The outside of the garment.
Dress Shirt or Blouse	14-20	Using more SPI allows the use of smaller diameter threads that will minimize seam Puckering.	Button-sew (4 hole button)	16	Button-sew machines are cycle machines with a predetermined number of stitches per cycle.
Casual Shirts, Blouses, Tops	10-14	Using more SPI will give more of a tailored stitch Appearance and better seam coverage when surging.	Buttonhole (1/2” purl or whip stitch)	85-90	Generally sewn vertically – approx. 85- 90 stitches with a lockstitch buttonhole Machine.

When setting standards for stitches per inch, you should always keep in mind that more stitches per inch used in a seam requires longer sewing cycles to complete the seam. Longer sewing cycles translates in to higher labor costs and lower production levels. Sewing machine sewing at 5,000 SPM (stitches per minute) at 8 SPI will sew 17.4 yards of seam per minute. Sewing machine sewing at 5,000 SPM at 14 SPI will sew 9.9 yards of seam per minute.

More stitches per inch will also consume for thread per inch of seam. This will contribute to higher seam strength and more elastic seams, but will also increase the consumption of thread required to sew the garment.

Therefore, the recommendations listed above are common stitch levels that provide adequate seam strength but also take into consideration the factors just mentioned.

When sewing knit fabrics, you should always check for excessive “seam grinning” of the seam; and also check for “stitch cracking”. “Seam grinning” occurs when thread stitch balance is too loose allowing the seam to open up too much when stress is applied to it. “Stitch cracking” is checked by applying pressure on the seam in the stitching direction. If the thread tensions are too tight or if you are not using enough stitches per inch, the threads will rupture as stress is applied on the seam. Therefore, the following recommendations have been made for the number of stitches per inch to be used on the following garments.

Common Garments Defects

Sewing Defects:

Ø  Open seams,

Ø  Wrong stitching techniques,

Ø  Non- matching threads,

Ø  Missing stitches,

Ø  Improper creasing of the garment,

Ø  Erroneous thread tension and raw edges.

Color Defects:

Ø  Variation of color between the sample and the final garment,

Ø  Wrong color combinations and mismatching dyes should always be avoided.

Size Defects:

Ø  Wrong gradation of sizes,

Ø  Difference in measurement of various parts of a garment like sleeves of XL size for body of L size garment can deteriorate the garments beyond repair.

Others Defects:

Ø  Broken buttons or defective buttons,

Ø  Broken snaps,

Ø  Broken stitches,

Ø  Different shades within the same garment,

Ø  Dropped stitches,

Ø  Exposed notches and raw edges,

Ø  Fabric defects,

Ø  Fabric holes,

Ø  Faulty zippers,

Ø  Loose or hanging  sewing threads,

Ø  Misaligned buttons and holes,

Ø  Missing buttons,

Ø  Needle cuts or chews,

Ø  Pulled yarn or loose yarn,

Ø  Stains,

Ø  Unfinished buttonhole,

Ø  Short zippers,

Ø  In appropriate trimmings etc.

Category of Zipper by Materials

Different kinds of zipper are used for different process and item. Such as Jacket, Sweat shirt, Denim Pants, Jogging suit, Sweater etc. Many times buyer asked for different type of zipper based on their garments item.

Mainly we can categorize the zipper in 02 (two) option

·         By Materials.

·         By Function.

Zipper Categories by materials:

o   Nylon (Polyester) Zipper

o   Plastic (Molded, Vislon), Zipper.

o   Metal (Aluminum, Brass, Anti-Brass, Nickel, Anti-Nickel)

Nylon (Polyester) Zipper:

Nylon/Polyester zippers are made by sewing monofilament – formed spiral teeth on to the tape. They are available in a wide range. Therefore, it is the most popular and widely used zippers.

Plastic (Molded, Vislon) Zipper:

Molded (plastic, injection, delrin, chunky) zippers are made by injecting plastic elements (acetyl copolymer) onto the tape. A wide range of colors and finished can be supplied to the zippers for the fashion industry.

Metal (Aluminum, Brass, Anti-Brass, Nickel, Anti-Nickel, Sliver etc):

Metal zippers, made from various dimension of half round wire, display distinctive personalities in the fashion-clothing design.

Zipper Categories by Functions

Different kinds of zipper are used for different process and item. Such as Jacket, Sweat shirt, Denim Pants, Jogging suit, Sweater etc. Many times buyer asked for different type of zipper based on their garments item.

Mainly we can categorize the zipper in 02 (two) option

·         By Materials.

·         By Function.

Zipper Categories by Functions:

·         Close-end zippers.

·         Open-end Separator zippers.

·         Two-way Separator.

·         Zipper with Double Sliders (Head-to-head)

·         Zipper With Double Sliders (Bottom to bottom)

Close-end zippers: are non-separating and are normally opened and closed with a slider. The bottom stop is made up of a single part and doesn’t allow complete separation of the chain. These zippers are used on trousers, jeans, bags, boots, etc.

Open-end (separating) zippers: have separated ends. The ending part is joined by a box and pin mechanism provided on the lower end of the zipper. The zippers are closed using sliders, and are normally used on jackets and other outerwears.

Two-way separating zippers: have separated ends as well. The bottom slider allows movement from the bottom of the zipper. These zippers are used in rainwears, sportswears, and sleeping bags.

 Two-way head to head zippers: have two sliders at the center of the chain when the zippers are closed. Head to head zippers can be opened by pulling the sliders towards the stops, but cannot be separated because the ending parts have two stops that cannot be divided. These zippers are mainly used for bags, backpacks, and luggage’s.

Two-way tail to tail zippers: have sliders on opposite ends when the zipper is closed. These zippers can be opened by pulling the sliders towards each other, but cannot be separated. They are used for overalls.