Seam Defects | Common Seam Quality Defects in Garments

Seam Defects
A seam is a method of joining two or more pieces of materials together by a row of stitching. The purpose of most of these seams is purely functional and can be called as constructional seams. Seams should be as flat as possible and unseen except those that are used for decorative purposes for garment design and line.When seaming then lots of defects occurred. These defects of seam are discussed below.

Improper stitch balance (301 lock-stitches):

The loops are seen either on the bottom side or topside of the seam. This is prominent with different coloured needle and bobbin threads and also, this defect comes where the stitch is too loose. To overcome this problem use a quality thread with consistent frictional characteristics, properly balance the stitch so that the needle and bobbin threads meet in the middle of the seam. Always start by checking the bobbin thread tension to make sure it is set correctly, so that the minimum thread tension is required to get a balanced stitch.

Improper stitch balance (401 chain stitch):

Where the loops on the bottom-side of the seam are inconsistent and do not appear uniform. To overcome this use a quality thread with consistent frictional characteristics, properly balance the stitch so that when the looper thread is unravelled, the needle loop lays over half way to the next needle loop on the underside of the seam.

Improper stitch balance (504 over-edge stitch):

Where the needle loop is not pulled up to the underside of the seam and the “purl” is not on the edge of the seam we get over edge stitch. To overcome this use a quality thread with consistent frictional characteristics and properly balance the stitch so that when the looper thread is unravelled, the needle loop lays over half way to the next needle loop on the underside of the seam.

Needle cutting on knits:

The needle holes appear along the stitch line that will eventually turn into a “run”. This defect is caused by the needle damaging the fabric as it is penetrating the seam. Make sure the proper thread size and needle type and size are being used for the fabric, the fabric has been properly stored to prevent drying out and finished properly and check with your fabric manufacturer.

Open seam – seam failure – fabric:

Open seam is where the stitch line is still intact but the yarns in the fabric have ruptured. Solutions are reinforcing stress points with bartacks. Make sure the bar tacks are the proper length and width for the application, make sure the patterns has been designed for proper fit, make sure the ideal seam construction is being used, and contact your fabric supplier.

Open seam – seam failure – stitch:

Where the threads in the seam have ruptured leaving a hole in the stitch line, caused by improper stitch for application, inadequate thread strength for seam and not enough stitches per inch. The solutions are using a better quality sewing thread, the proper size thread for the application. For knit fabrics, check for “stitch cracking” caused by not enough stitches per inch, improper seam width or needle spacing for application, improper stitch balance and improper thread selection.

Puckered seams (knits and stretch woven ):

Puckered seam is where the seam does not lay flat after stitching mainly due to too much stretching of the fabric while sewing. The solutions include setting the sewing machines properly for the fabric if sewing machines are equipped with differential feed, using minimum presser foot pressure during sewing and adopting correct handling techniques.

Excessive seam puckering (woven):

The seam does not lay flat and smooth along the stitch line. The reasons may be ‘feed puckering’, where the plies of fabric in the seam are not being aligned properly during sewing, ‘tension puckering’ where the thread has been stretched and sewn into the seam causing the seam to draw back and pucker and yarn displacement or ‘structural jamming’ caused by sewing seams with too large of thread causing displacement of yarn in the seam. To avoid this use the correct thread type and size for the fabric, (In many cases, a smaller, higher tenacity thread is required to minimize seam puckering but maintain seam strength), sew with minimum sewing tension to get a balanced stitch, make sure that machines are set up properly for the fabric being sewn and check for proper operator handling techniques.

Ragged/Inconsistent edge:

Over-edge or safety stitch seams are where the edge of the seam is either extremely “ragged” or “rolls” inside the stitch. To avoid this sharpen the sewing machine knives and change regularly, adjust the knives properly in relationship to the “stitch tongue” on the needle plate to obtain the proper seam width or width bite.

Re-stitched seams / broken stitches:

This is the defect where a “splice” occurs on the stitch line. This is highly objectionable in top stitching. It is caused by thread breaks or thread run-out during sewing, or cut or broken stitches during a subsequent treatment of the finished product (i.e., stone washing). To avoid this use a better quality sewing thread. This may include going to a higher performance thread designed to minimize sewing interruptions. Ensure proper machine maintenance and sewing machine adjustments. Make sure sewing machines are properly maintained and adjusted for the fabric and sewing operation. Observe sewing operators for correct material handling techniques.

Re-stitched seams in jeans:

If there is a splice on stitch line and occurs on top stitching, it is objectionable. It may be caused by breaks or thread run out during sewing, or cut or broken stitches during a subsequent treatment of the finished product. The solutions include using better quality sewing thread, ensuring proper machine maintenance and adjustments of sewing machine and observing sewing operators for correct material handling techniques.

Re-stitched seams in jeans

Broken stitches (needle cutting in jeans):

When a thread is being broken one seam crosses over another seam resulting in stitch failure like bartacks on top of waistband stitching, seat seam on top of riser seam. Using the proper thread and maintaining the proper stitch balance can minimize broken stitches due to needle cutting. Use of higher performance perma core or D-core thread, using a larger diameter thread on operations where the thread is being cut, making sure the proper stitch balance is being used, using needles with the correct point and changing the needles at regular intervals on operations are the remedies.

Broken stitches – needle cutting in jeans

Broken stitches (abrasion in jeans):

The thread on the stitch line is broken during stone washing, sand blasting, hand sanding, etc. Broken stitches must be repaired by re stitching over the top of the stitch-line. The prevention can be done by use of higher performance perma core or D-core thread, use of larger diameter thread on operations where excessive abrasion is occurring (e.g. waist band), ensuring that stitches balance properly, using air entangled thread in the looper due to its lower seam profile making it less susceptible to abrasion (in yoke, seat and waistband seam) and monitoring the finishing cycle.

Broken stitches – abrasion in jeans

Excessive seam grin:

Excessive grin is where the stitch balance is not properly adjusted (stitch too loose) and the seam opens up. To check for seam grin, apply normal seam stress across the seam and then remove the stress. If the seam remains opened, then the seam has too much “grin through”. To correct, readjust the sewing machine thread tensions so that the proper stitch balance is achieved. Too much tension will cause other problems including seam failures (stitch cracking), excessive thread breakage, and skipped stitches.

Seam failure:

Seam Slippage is where the yarns in the fabric pull out of the seam from the edge. This often occurs on fabrics constructed of continuous filament yarns that are very smooth and have a slick surface and in loosely constructed fabrics. To avoid consider changing the seam construction to a French seam construction, increase the seam width or width of bite, optimize the stitches per inch and contact your fabric supplier.

Skipped stitches:

This is where the stitch length is inconsistent, possibly appearing as double the normal stitch length; or that the threads in the stitch are not properly connected together. It is caused by the stitch forming device in the sewing machine missing the thread loop during stitch formation causing a defective stitch. On looper type stitches, this will allow the stitch to unravel causing seam failure. To avoid this use a better quality sewing thread, ensure proper machine maintenance and sewing machine adjustments, make sure that sewing machines are properly maintained and adjusted for the fabric and sewing operation. Observe sewing operators for correct material handling techniques.

Skipped stitches in jeans:

Where the stitch forming device misses the needle loop or the needle misses the looper loop. Skips are usually found where one seam crosses another seam and most of the time occurs right before or right after heavy thickness. The solutions are using core-spun thread, minimum thread tension to get a balanced stitch, the ideal foot, feed and plate that help to minimize flagging, training sewing operators not to stop on the thickness, making sure the machine is feeding properly without stalling and the machine is not back-feeding.

Skipped stitches in jeans

Unravelling buttons:

This is where a tail of thread is visible on the topside of the button and when pulled, the button falls off. To avoid this use a quality sewing thread to minimize skipped stitches, specify attaching the buttons with a lockstitch instead of a single thread chain stitch button sewing machine.

Broken stitches (due to chemical degradation in jeans):

The thread in seam is degraded by the chemicals used during laundering resulting in loss or change of colour and seam failure. The solutions include using higher performance Perma Core NWT that has higher resistance to chemical degradation. It is recommended to go for larger thread sizes when the denim garments are subjected to harsh chemical washes. Ensure proper water temperature and pH levels, and proper amount and sequence of chemical dispersion as per guidelines and proper rinsing and neutralizing. Monitor the drying process, cycle time, and temperature

Unravelling seams in jeans:

Generally occurs on 401 chain stitch seams where either the stitch has been broken or a skipped stitch has occurred. This will cause seam failure unless the seam is re stitched. The solutions include using a high performance Perma Core or DCore thread that will minimize broken stitches and skipped stitches, ensuring proper maintenance and adjustments of sewing machine and training sewing operators for correct material handling techniques.

Unravelling seams in jeans

Sagging or rolling pockets: 

Where the pocket does not lay flat and rolls over after laundering. The solutions include making sure the sewing operators are not holding back excessively when setting the front pocket, the hem is formed properly and that excessive fabric is not being put into the folder that will cause the hem to roll over. Ensure that pocket is cut properly and pocket curve is not too deep. Use a reinforcement tape on the inside of the pocket that may help prevent the front panel from stretching along the bias where the front pocket is set. Select fabric construction as the type and weight of fabric also can contribute for this.

Sagging or rolling pockets

Ragged / Inconsistent edge:

This is where the edge of the seam is either extremely “Ragged” or “Rolls” inside the stitch. To avoid this make sure the sewing machine knives are sharpened and changed often. The knives should be adjusted properly in relation to the “Stitch Tongue” on the needle plate to obtain the proper seam width or width bite.

Ragged / Inconsistent edge

Wavy seam on stretch denim:

Where the seam does not lie flat and is wavy due to the fabric stretching as it was sewn or during subsequent laundering and handling operations. To avoid this use minimum presser foot pressure. Instruct sewing operators to use proper handling techniques and not stretch the fabric as they are making seam. Where available, use differential feed to compensate for the stretch of the fabric.

Wavy seam on stretch denim

Ropy hem:

Ropy hem is where hem is not laying flat and is skewed in appearance, usually caused by poor operator handling. Sewing operator should make sure they get the hem started correctly in the folder before they start sewing and should not hold back excessively as the seam is being sewn. Use minimum roller or presser foot pressure.

Ropy hem

Twisted legs in jeans:

Twisted leg is where the side seam twists around to the front of the pant and distorts the appearance of the jeans, usually caused by poor operator handling. To avoid this sewing operator should match the front and back properly so they come out the same length. Notches might be used to ensure proper alignment. Ensure that operator does not trim off the front or back with scissors to make them come out the same length. Make sure the cut parts are of equal length coming to the assembly operation. Check fabric quality and cutting for proper skew. Make sure the sewing machine is adjusted properly for uniform feeding of the top and bottom plies.

Twisted legs in jeans

Disappearing stitches in stretch denim:

Where the thread looks much smaller on seams sewn in the warp direction than in the weft direction of the fabric. To prevent this use a heavier thread size on top stitching [120 to 150 Tex], go to a longer stitch length [from 8 to 6 S.P.I] and make sure the thread tensions are as loose as possible so the thread sits on top of the fabric rather than burying in the fabric on seams sewn in the warp.

Disappearing stitches in stretch denim

Thread discolouration after laundry in jeans:

The thread picks up the indigo dyes from the fabric giving the thread a ‘dirty’ appearance. A common discoloration would be the pick up of a greenish or turquoise tint. The main reasons are improper pH level, improper water temperature, improper chemical selection and shortcuts on wash methods. The solutions for this are using thread with proper colour fastness characteristics, correct pH level and low water temperature during laundry, using the proper chemicals and laundry cycles, and using denimcol PCC or similar additive in wash. Do not over load washers with too many garments at one time.

Thread discolouration after laundry in jeans

Poor colour fastness after laundry:

The thread does not wash down consistently in the garment or changes to a different colour all together. The normal reasons are mixing threads in a garment, using threads with different colour fastness and not doing preproduction testing. To avoid this use thread with proper colour fastness characteristics, use threads from same thread supplier and do not mix threads in a garment. Always do preproduction testing on denim garments using new colours to assure that they will meet the requirements. Make sure sewing operators select thread by type and colour number and do not just pick a thread off the shelf because it looks close in colour.

Poor colour fastness after laundry

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