Monday, 2 February 2015

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 stitchSlipped 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 StitchesBroken 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.
- See more at: http://textilehelpline.com/problems-of-stitch-formation-in-sewing-machine/#sthash.dSAX

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