Troubles And Corrective Measures In Sewing - JUKI MEB-3810N Series Instruction Manual

12. TROUBLES AND CORRECTIVE MEASURES IN SEWING

Phenomenon
1. Stitch skipping • 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.
• When changing • Improper adjustment of the clearance between the
needle size 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 fit the kind of throat plate
(needle size used).
• W h e n k i n d o f • Thread which is difficult to make loops is used.
thread is affected (Hard-to-slide thread or the like)
• W h e n s e w i n g • The needle is bent at the thick section of the ma-
heavy-weight ma- terial and stitch skipping occurs.
terials • In case of the cut-before knife, the inside needle
is bent at the cutting section and stitch skipping
occurs.
2. Stitch skipping at • The left-hand spreader is installed incorrectly.
the sewing start • 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.
3. Stitch skipping at • The clearance between the presser foot and the
eyelet section needle entry point is too large.
• The cloth is flopping.
• 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.
4. Seam splitting at the • The feeding amount of needle thread is insufficient.
sewing end
• The timing of the right-hand looper is too late.
• The opening amount of the right-hand spreader is
insufficient.
• The gimp is too hard.
5. Needle thread break- • The needle thread tension is too high.
age
• 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.
Cause
• Check and replace the needle.
• Use DO x 558 needle.
• Adjust the clearance at the time of inside needle or
• 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
• Remove the cloth waste from the spreader. Replace
• 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
• Check the height of the needle bar and properly
• Check the height of the needle bar and properly
• Adjust the clearance at the time of inside needle or
• Adjust the timing to open/close the spreader with
• 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
• Re-set the cut space.
• Check the installing position and adjust it.
• Check the timing between the needle and the
• 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.
• Check the clearance and adjust it properly.
• Decrease the sewing speed of eyelet section.
• Adjust the height of the needle bar.
• Adjust the height of the needle bar.
• Adjust the feeding amount of needle thread.
• Check and adjust the timing between the needle
• Check and adjust the opening amount of the spread-
• Replace the gimp. Check the thread path of gimp.
• Adjust the sewing conditions to obtain an appropri-
• Check and adjust the clearance.
• Check and replace the respective parts.
• Replace the needle with a proper one.
• Check and replace the needle.
– 99 –
Corrective measure
outside needle.
stitch bite width used.
the spreader with a new one.
replace it with a new one.
adjust it.
adjust it.
outside needle with the needle size used.
the needle size used.
base line offset.
looper, and adjust it.
Adjust the position of the presser foot.
Adjust the looper timing.
Adjust the looper timing.
and the looper.
er.
ate thread tension.
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