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9.TROUBLES AND CORRECTIVE MEASURES (WITH REGARD TO MECHANICAL COMPONENTS)
1
.
Several stitches skip or thread comes
off at the start of sewing.
1-1) Length of thread remaining after thread
trimming is too short.
1-2) Needle thread feeding amount is
insufficient.
1-3) Thread trimming failure because the
bobbin thread is too short.
1-4) Failed clamp of the bobbin thread
1-5) The needle thread and bobbin thread
do not neatly interlace with each other
at the start of sewing.
1-6) The needle thread is not under the
presser foot when the wiper sweeps the
thread and is free.
l-7) Idle stitches are made at the start of
sewing.
1)-A Tension provided by the pre-tension disk
is too high.
1)-B The tension disk fails to rise at the time of
thread trimming.
1)-C The tension disk comes in contact with the
thread take-up spring guard.
1)-D The cam timing is excessively advanced.
2)-A Stroke of the thread feeding wire is too
small.
2)-B The thread feeding wire has been
improperly positioned.
2)-C The thread slips off the thread feeding wire
and take-up thread guide.
3)-A Bobbin thread tension is too high.
4)-A
5)-A Sewing speed at the start of sewing is too
high. This prevents the needle thread and
bobbin thread from smoothly interlacing
with each other.
6)-A Needle thread is not early retained with the
presser foot and the throat plate.
7)-A The needle thread and bobbin thread do
not interlace with each other because the
material makes no resistance to the
threads.
Loosen the pre-tension disk as long as the thread slips in the tension disk.
Inspect the thread tension releasing solenoid components and adjust them, if necessary.
Correct the position of the tension disk and thread take-up spring guard so that they do not
come in contact with each other.
Properly adjust the cam timing.
Lengthen the stroke of the thread feeding wire.
Properly adjust the position of the thread feeding wire.
Re-thread the thread feeding wire and take-up thread guide. If the thread frequently slips off
the thread feeding wire, replace the wire with a new one.
Reduce bobbin thread tension to such an ertent that thread tension is sufficiently obtained.
Enter 3 stitches at soft start (1,200 rpm).
Create a custom pattern as shown below and make a larger back-tack stitch length than the
needle hole width of the presser. The stitch length of 1.6 to 2 mm is recommended for reference.
Place the threads under the presser foot and start the sewing machine while holding the threads
there.
Trouble
Cause 1
Cause 2
Corrective measure and adjusting procedure
3rd stitch
2nd stutch
1.6
4
3
2
1st stitch
1
