– 99 –
12. TROUBLES AND CORRECTIVE MEASURES IN SEWING
Phenomenon Cause Corrective measure Page
1. Stitch skipping
• When changing
needle size
• When kind of
thread is affected
• When sewing
heavy-weight ma-
terials
• The needle is bent. There is a scratch on the
needle. The needle is incorrectly attached.
• Kind of needle is wrong.
• The clearance between the needle and the looper
is too large.
• The clearance between the needle and the needle
guard is too large or the needle and the needle
guard come in excessive contact with each other.
• The clearance between the needle and the looper
varies according to the turning angle (0˚, 90˚ and
180˚).
• Improper adjustment of the timing between the
needle and the looper
• Improper adjustment of the timing to open/close
the spreader.
The spreader comes in contact with the needle.
• Motion to open/close the spreader is not smooth.
• The clearance between the presser foot and the
needle entry point is too large.
• Thread tension is not proper.
• The blade point of looper has worn out.
• Improper adjustment of the height of the needle
bar
• Loop cannot be scooped since it is not formed.
• Improper adjustment of the clearance between the
needle and the looper
• Improper adjustment of the timing to open/close
the spreader.
The spreader comes in contact with the needle.
• The needle does not t the kind of throat plate
(needle size used).
• Thread which is difcult to make loops is used.
(Hard-to-slide thread or the like)
• The needle is bent at the thick section of the ma-
terial and stitch skipping occurs.
• In case of the cut-before knife, the inside needle
is bent at the cutting section and stitch skipping
occurs.
• Check and replace the needle.
• Use DO x 558 needle.
• Adjust the clearance at the time of inside needle or
outside needle.
• Check and adjust the clearance.
• Adjust the center of the needle.
• Adjust the timing with the stitch bite width used.
• Adjust the timing to open/close the spreader by the
stitch bite width used.
• Remove the cloth waste from the spreader. Replace
the spreader with a new one.
• Check the clearance and properly adjust it.
• Set the thread tension to the proper value.
• Correct the looper with oil-stone or the like, or
replace it with a new one.
• Check the height of the needle bar and properly
adjust it.
• Check the height of the needle bar and properly
adjust it.
• Adjust the clearance at the time of inside needle or
outside needle with the needle size used.
• Adjust the timing to open/close the spreader with
the needle size used.
• Use the throat plate suitable for the needle.
• Decrease the needle thread tension.
• Reduce the sewing speed of the sewing machine.
• Change the needle to a thicker one. Adjust the stitch
base line offset.
• Re-set the cut space.
37
1
84
84
-
79
86
85, 86, 90
68、88
44、73
84
82
82
84
86
96
44
63
37
54、57
2. Stitch skipping at
the sewing start
• The left-hand spreader is installed incorrectly.
• The timing of the right-hand looper is too early.
• The clearance between the presser foot and the
needle entry point is too large.
• The looper is bent. There are scratches on the
looper.
• Length of the needle thread remaining on the
needle is too short.
• Looper thread clamp/looper thread presser is
weak and the looper thread comes off at the start
of sewing.
• Check the installing position and adjust it.
• Check the timing between the needle and the
looper, and adjust it.
• Check the clearance and adjust it.
• Check the looper and replace it with a new one.
• Properly adjust the needle thread drawing amount.
• Check the needle clamp pressure.
85
79
68, 88
79
69
89
3. Stitch skipping at
eyelet section
• The clearance between the presser foot and the
needle entry point is too large.
• The cloth is opping.
• Needle thread loop is too large and falls.
As a result, it is not caught by the looper.
• Needle thread loop cannot be made.
As a result, the looper cannot catch the thread.
• Check the clearance and adjust it properly.
• Decrease the sewing speed of eyelet section.
Adjust the position of the presser foot.
• Adjust the height of the needle bar.
Adjust the looper timing.
• Adjust the height of the needle bar.
Adjust the looper timing.
68, 88
63
88
82
79
82
79
4. Seam splitting at the
sewing end
• The feeding amount of needle thread is insufcient.
• The timing of the right-hand looper is too late.
• The opening amount of the right-hand spreader is
insufcient.
• The gimp is too hard.
• Adjust the feeding amount of needle thread.
• Check and adjust the timing between the needle
and the looper.
• Check and adjust the opening amount of the spread-
er.
• Replace the gimp. Check the thread path of gimp.
69
79
86
40, 70
5. Needle thread break-
age
• The needle thread tension is too high.
• The needle comes in contact with the blade point
of the looper.
• The thread paths in the needle, loopers, spreaders,
throat plate, etc. have become worn out or contain
scratches.
• The thread is too thick or too thin for the needle.
• There are scratches in the needle hole or needle
slot.
• Adjust the sewing conditions to obtain an appropri-
ate thread tension.
• Check and adjust the clearance.
• Check and replace the respective parts.
• Replace the needle with a proper one.
• Check and replace the needle.
44, 73
84
37, 84, 85
37
37
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