Difference Between Seam Strength and Seam Slippage
Both the parameters measure the performance of seam. Seam strength referes to the strength when seam finally ruptures or when the fabric breaks.
However before rupturing there is an unacceptable opening in the seam which makes the seam 'failed' commercially even when there is no visible rupture. Seam slippage measures that.
Seam strength depends upon stitch type, thread strength, stitches per inch, thread tension, seam type and seam efficiency of the material.
Seam slippage depends upon the stitch rate, the weave structure of the fabric and the width of the seam allowance.
There is another term called 'yarn slippage' which measures the shifting of warp yarn over weft yarn to render the garment unusuable.
Yarn slippage depends upon a low number of warp or filling yarn, two shallow seam allowance, too tight a fit and improper seam construction.
Find Pictures of Seam Quality Defects Improper Stitch Balance - 301 Lockstitch |
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| DESCRIPTION: Where loops are seen either on the bottomside or topside of the seam. This is particularly evident with different colored needle and bobbin threads. Also, where the stitch is too loose. SOLUTIONS: 1) Use a quality thread with consistent frictional characteristics; 2) 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. | Poor Stitch Balance - Too Loose
 Proper Stitch Balance
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| Improper Stitch Balance - 401 Chainstitch |
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| DESCRIPTION: Where the loops on the bottom-side of the seam are inconsistent and do not appear uniform. SOLUTIONS: 1) Use a quality thread with consistent frictional characteristics; 2) Properly balance the stitch so that when the looper thread is unraveled, the needle loop lays over half way to the next needle loop on the underside of the seam. | Stitch Too Loose
Proper Stitch Balance
Proper Stitch Balance
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| Improper Stitch Balance - 504 Overedge Stitch |
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| DESCRIPTION: 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. SOLUTIONS: 1) Use a quality thread with consistent frictional characteristics; 2) Properly balance the stitch so that when the looper thread is unraveled, the needle loop lays over half way to the next needle loop on the underside of the seam. | Improper Stitch Balance
Purl Not on Edge
Proper Stitch Balance
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| Needle Cutting on Knits |
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| DESCRIPTION: Where needle holes appear along the stitchline that will eventually turn into a "run". Generally caused by the needle damaging the fabric as it is penetrating the seam. MINIMIZING NEEDLE CUTTING ON KNITS: 1) Make sure the proper thread size and needle type and size are being used for the fabric (See Reducing Needle Cutting.); 2) Make sure the fabric has been properly stored to prevent drying out and has been finished properly; 3) Check with your fabric manufacturer. | 
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| Open Seam - Seam Failure - Fabric |
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| DESCRIPTION: Where the stitch line is still intact but the yarns in the fabric have ruptured. MINIMIZING SEAM FAILURES - FABRIC: 1) Reinforce stress points with Bartacks. Make sure the bartacks are the proper length and width for the application; 2) Check to make sure the patterns have been designed for proper fit; 3) Make sure the ideal seam construction is being used; 4) Contact your fabric supplier. | Open Seam Failure - Fabric
 Bartacks Used to Reinforce Fly Seam
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| Open Seam - Seam Failure - Stitch |
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| DESCRIPTION: Where the threads in the seam have ruptured leaving a hole in the stitchline. Caused by 1) Improper stitch for application; 2) Inadequate thread strength for seam; 3) Not enough stitches per inch. MINIMIZING SEAM FAILURES - STITCH: 1) Use a better quality sewing thread. This may include going to a higher performance thread designed to give greater seam performance. (See the Thread Selection Guide.); 2) Use the proper size thread for the application; 3) For knit fabrics, check for "Stitch Cracking". Stitch Cracking can be caused by any of the following: not enough stitches per inch; improper seam width or needle spacing for application; improper stitch balance; and improper thread selection. | Seam Failure on Stretch Knit Fabric
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| Puckered Seams - Knits & Stretch Wovens |
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| DESCRIPTION: Where the seam does not lay flat after stitching.
SOLUTIONS: 1) If sewing machines are equipped with differential feed, set them properly for the fabric; 2) Use minimum presser foot pressure during sewing; and 3) Observe operator for correct handling techniques. Too much stretching of the fabric by the sewing operator will cause this problem. (See Sewing Stretch Knits.) | 
Stretch Denim - Wavy Seams
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| Excessive Seam Puckering - Wovens |
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| DESCRIPTION: Where the seam does not lay flat and smooth along the stitchline. Caused by one of the following:
1) Feed Puckering - where the plies of fabric in the seam are not being aligned properly during sewing; 2) Tension Puckering - where the thread has been stretched and sewn into the seam. The thread then causes the seam to draw back and pucker; 3) Yarn Displacement or structural jamming - caused by sewing seams with too large of thread that causes the yarns in the seam to be displaced, giving a puckered appearance. MINIMIZING EXCESSIVE SEAM PUCKERING: 1) 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 (See the Thread Selection Guide or Minimizing Seam Puckering); 2) Sew with minimum sewing tension to get a balanced stitch; 3) Make sure machines are set up properly for the fabric being sewn; 4) Check for proper operator handling techniques. | 
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| Ragged/Inconsistent Edge - Overedge or Safetystitch Seams |
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| DESCRIPTION: Where the edge of the seam is either extremely "ragged" or "rolls" inside the stitch.
SOLUTIONS: 1) Make sure the sewing machine knives are sharpened and changed often; 2) The knives should be adjusted properly in relationship to the "stitch tongue" on the needle plate to obtain the proper seam width or width bite. In the photo, the trimming knives have been set wider than the "stitch tongue" on the needle plate causing the "ropy" appearance. | 
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| Restitched Seams / Broken Stitches |
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DESCRIPTION: Where a "splice" occurs on the stitch line. If this occurs on Topstitching, then the seam does not appear to be 1st quality merchandise. Caused by 1) thread breaks or thread run-out during sewing; or 2) cut or broken stitches during a subsequent treatment of the finished product (i.e., stone washing).
MINIMIZING THREAD BREAKAGE: 1) Use a better quality sewing thread. This may include going to a higher performance thread designed to minimize sewing interruptions. (See the Thread Selection Guide and/or Minimizing Thread Breakage & Skipped Stitches); 2) Insure proper machine maintenance and sewing machine adjustments; 3) Make sure sewing machines are properly maintained and adjusted for the fabric and sewing operation. (See Machine Maintenance Checklist.); 4) Observe sewing operators for correct material handling techniques. | Excessive Restitched Seams
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| Excessive Seam Grin |
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DESCRIPTION: Where the stitch balance is not properly adjusted (stitch too loose) and you can see the seam opening 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".
SOLUTIONS: 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 Grinning on Woven Fabric
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| Seam Failure - Seam Slippage |
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| DESCRIPTION: 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. Also caused by loosely constructed fabrics. MINIMIZING SEAM FAILURES - SEAM SLIPPAGE: 1) Consider changing the seam construction to a French seam construction; 2) Increase the seam width or width of bite; 3) Optimize the stitches per inch; 4) Contact your fabric supplier. | Seam Slippage on Rayon Fabric
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| Unraveling Buttons |
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DESCRIPTION: Where a tail of thread is visible on the topside of the button and when pulled, the button falls off.
SOLUTIONS: 1) Use a quality sewing thread to minimize skipped stitches; 2) Specify attaching the buttons with a Lockstitch instead of a single thread Chainstitch Buttonsewing machine. |  |
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