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3. TROUBLESHOOTING
3-1. Troubles with sewing and corrective measures
Trouble
① Stitches are slipped at the start.
1. The needle
thread slips off
at the start of bar-
tacking.
② The needle thread remaining on
③ The bobbin thread is too short.
④ Needle thread tension at 1st stitch
⑤ Thread clamp is unstable (material
⑥ Pitch at 1st stitch is too small.
⑦ The bird's nest reducing operation
⑧ During the bird's nest reducing
⑨ When the bird's nest reducing
① The bobbin case holder has
2. Thread often
breaks or
synthetic fiber
② The needle hole guide has
thread splits
finely.
③ The needle strikes the intermediate
④ The needle thread tension is too
⑤ The tension of the thread take-up
⑥ The synthetic fiber thread melts
⑦ When taking up thread, thread is
Cause
the needle after thread trimming
is too short.
is too high.
is apt to be expanded, thread is
hard to slide, thread is thick, etc.).
is poorly adjusted. As a result,
the thread is not trimmed at the
predetermined position.
operation, the number of stitches
at which the thread trimmer trims
the thread is not correct.
function is set to ON, the needle
thread end is failed to be brought
to the hook side and the bobbin
thread is trimmed.
scratches.
scratches.
presser foot.
high.
spring is too high.
due to heat generated on the
needle.
pierced with needle tip.
Corrective measures
○ Adjust the clearance between the needle
and the shuttle to 0.05 to 0.15 mm.
○ Set soft-start sewing at the start of
bartacking.
○ Correct the thread tension release timing
of the thread tension controller No. 1.
○ Increase the tension of the thread take-
up spring, or decrease the tension of the
thread tension controller No. 1.
○ Decrease the tension of the bobbin thread.
○ Increase the clearance between the
needle hole guide and the counter knife.
○ Decrease the tension at 1st stitch.
○ Decrease the number of rotation at 1st
stitch at the sewing start. (Extent of 600
to 1,000 sti/min)
○ Increase the number of stitches of thread
clamp to 3 to 4 stitches.
○ Make the pitch at 1st stitch longer.
○ Decrease the needle thread tension at
1st stitch.
○ Adjust the position of moving knife before
it trims the thread. (1.1 ± 0.1 mm)
○ Set the number of stitches to be sewn
before thread trimming to the correct
setting using the memory switch U319.
(Thin thread: 3, thick thread: 2)
○ Use the wiper.
○ If the wiper wiping operation is defective,
the position of wiper should be adjusted.
○ Adjust the length of needle thread
remaining on the material to the optimum
value. (40 mm to 50 mm)
○ Take it out and remove the scratches
using a fine whetstone or buff.
○ Buff or replace it.
○ Correct the position of the intermediate
presser foot.
○ Reduce the needle thread tension.
○ Reduce the tension.
○ Use silicone oil.
○ Lower the needle bar height from the
engraved marker line by a half of the line
to as much as the line.
○ Check the rough state of needle tip.
○ Use the ball-pointed needle.
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