Troubles And Corrective Measures (Sewing Conditions) - JUKI AMS-224EN-4530 Instruction Manuals

1-14. Troubles and corrective measures (Sewing conditions)

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
⑤ Thread clamp is unstable (mate-
⑥ Pitch at 1st stitch is too small.
① The shuttle or the driver has
2. Thread often
breaks or syn-
② The needle hole guide has
thetic fiber thread
splits finely.
③ The needle comes in contact with
④ Fibrous dust is in the groove of
⑤ The needle thread tension is too high.
⑥ The tension of the thread take-up
⑦ The synthetic fiber thread melts due
⑧ When taking up thread, thread is
① The needle is bent.
3. The needle often
② The needle comes in contact with
breaks.
③ The needle is too thin for the
④ The driver excessively bends the
① The counter knife is dull.
4. Threads are not
② The difference in level between
trimmed.
③ The moving knife has been im-
④ The last stitch is skipped.
⑤ Bobbin thread tension is too low.
(Bobbin thread only)
⑥ Flopping of cloth
⑦ Pitch of the last stitch is small.
⑧ Hole of the needle hole guide is
Cause
the needle after thread trimming
is too short.
stitch is too high.
rial is apt to be expanded, thread
is hard to slide, thread is thick,
etc.).
scratches.
scratches.
the work clamp.
the shuttle race.
spring is too high.
to heat generated on the needle.
pierced with needle tip.
the work clamp.
material.
needle.
the needle hole guide and the
counter knife is not enough.
properly positioned.
small.
– 113 –
Corrective measures
◦ Adjust the clearance between the needle
and the shuttle to 0.05 to 0.1 mm.
◦ Set soft-start sewing at the start of bart-
acking.
◦ Correct the thread tension release timing
of the thread tension controller No. 2.
◦ 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.
◦ Take it out and remove the scratches
using a fine whetstone or buff.
◦ Buff or replace it.
◦ Adjust the position of the work clamp.
◦ Take out the shuttle and remove the
fibrous dust from the shuttle race.
◦ 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.
◦ Replace the bent needle.
◦ Adjust the position of the work clamp.
◦ Replace it with a thicker needle accord-
ing to the material.
◦ Correctly position the needle and the
shuttle.
◦ Replace the counter knife.
◦ Increase the bend of the counter knife.
◦ Correct the position of the moving knife.
◦ Correct the timing between the needle
and the shuttle.
◦ In crease the bobbin thread tension.
◦ Lower the intermediate presser height of
the last stitch.
◦ Make the clearance between presser
and needle small.
◦ Decrease the stroke of the intermediate
presser.
◦ Make the pitch of the last stitch large.
◦ Replace the needle hole guide with one
with larger hole.
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