Problems of Stitch Formation in Sewing Machine

Problems of Stitch Formation in Sewing Machine

Introduction:

The first step in producing a stitch on a sewing machine is the formation of the needle thread loop. Proper stitch formation of this loop depends on the tendency of the thread to bulge away from the needle. Many problems occur during stitch formation in sewing machine. Major problems of stitch formation and their causes and remedies are given below.

Problems of stitch formation:

Slipped stitch:

Slipped stitch

Stitches in the seam line are present in a regular wise. If the interloping or interlacing between top & bottom thread of stitch is not take place or missed is known as slipped stitch or skipped stitch. This is more harmful in case of chain stitch than lock stitch. The followings are the causes & remedies of slipped stitch formation given by a table:

No.	Causes	Remedies
01	If hook or looper & needle are not inserted in loop of thread in time.	1. Examine the setting & timing between needle & hook or looper. 2. Placing of needle properly. 3. More secure needle should be used.
02	Irregular thread tension on upper or lower loop.	The tension of the thread should again be adjusted.
03	Due to needle deflection.	Needle to be changed.
04	If needle thread loop size is too small.	Needle size & thread size must be adjusted.

Staggered stitch:

If the stitches produced by needle are not parallel or become curvy to sewing line is known as staggered stitch. The followings are the causes & remedies of staggered stitch formation given by a table:

No.	Causes	Remedies
01	Needle deflection.	1. Increase the needle size 2. Tapered needle should be used.
02	Due to wrong blunt needle point.	Needle to be changed.
03	Wrong adjustment of needle & thread size.	Needle size & thread size to be changed.
04	Deflected motion of feed dog.	Motion of feed dog to be adjusted.
05	If fabrics are not controlled properly in the feed mechanism.	1. The pressure of pressure foot must be adjusted accurately. 2. Feed mechanism to be changed.

Unbalance stitch:

This type of defect is found in lock stitch machine. If the interlacement of threads are not take place in the middle (i.e. if the interlacement is taken place in the upper or lower position from the middle) of two layers of fabrics then it is known as unbalance stitch. The following are the causes & remedies of unbalanced stitch formation given by a table:

No.	Causes	Remedies
01	Wrong tension of sewing thread.	1. Setting of proper tension to the sewing thread. 2. Proper care to the twisting of the thread during sewing.
02	Used wrong thread path	Use of right thread path.
03	Wrong adjustment of needle thread path.	Use of right thread path.
04	Snagging of needle with bobbin case & positioning finger.	1. Bobbin case to be smooth. 2. The positioning finger to be set again.
05	If the thread are not lubricated.	1. Better qualities of thread must be used. 2. Thread must be lubricated.

Variable stitch density:

It must need to be the same amount of stitches per unit length. If it is not, then it is called variable stitch density. The main cause of variable stitch density is irregular feed of fabric due to insufficient pressure of pressure foot. The following are the cause & remedies of variable stitch density formation given by a table:

No.	Causes	Remedies
01	Improper unwinding of thread from package during sewing.	The position of thread guide must be 2.5 times higher than the position of thread package. Also proper care should be kept to the thread package not to tiling
02	Twisting of needle thread in the bottom of the thread package.	Foam pad must be used to the bottom of the thread package.
03	Snarling of thread before tension disk.	Winding of more threads in the thread guide & to be kept less tension to the tensioning disk.
04	Twisting of thread in the thread guide.	Proper threading of sewing thread during sewing.
05	More tension to the thread.	The tension of thread should be less or use of high strength threads.
06	Use of broken check spring.	Check spring to be changed.
07	If the edge of the throat plate, hook point, needle guard, bobbin case, needle groove, needle eye & so on are sharpened.	The edges must be smooth & needle must be changed as needed.
08	Fraying of thread in the needle.	Fine thread must be used or to be used heavy needle.
09	Becoming more heated of thread.	High quality needle must be used. Needle lubricant must be used.

Frequent thread breakage:

This breakage of thread again & again during sewing & also, there needs more time & which is harmful for production. Specially, when there needs to open out of sewing to solve the problem. The following are the causes & remedies of frequent thread breakage formation given by a table:

No.	Causes	Remedies
01	Wrong winding of threads on to the bobbin.	1. Proper winding of threads on to the bobbin. 2. Pre-wound bobbin may be used.
02	More tension to the bobbin threads or more rotating of bobbin.	1. The tension must be adjusted to the bobbin threads. 2. Use of washer to prevent the more rotating of bobbin.
03	If the edges bobbin case, looper eye & so on are more sharpened.	The edges to be smooth.
04	Wrong fitting of bobbin case.	1. Examine the size & type of bobbin. 2. Examine the damaging of bobbin case.

Broken Stitches:

Broken Stitches

When stitches are broken during sewing is called broken stitch.

Cause: Where the thread is being broken where one seam crosses another seam (ex: bar tacks on top of waistband stitching, seat seam on top of riser seam.)

Remedies: Where the thread is being cut, use a large diameter thread on operations. Make sure the proper stitch balance is being used. Use needles with appropriate needle point. At regular intervals on operations change the needles where they are occurring frequently.

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