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7. Needle thread is not trimmed at the time of
idle stitching.
8. Wiper fails to sweep thread.
(Bird's nest prevention type)
9. Defective needle thread clamp
10.Air pressure is decreased, suction force
is decreased and thread is not sucked.
11.Air pressure is decreased and thread is
not sucked since dust bag clogs with too
much thread waste.
Stroke of the thread take-up spring is too large.
When sewing product is thin and needle thread tension is
low, thread draw-out amount is excessive and wiper fails
to sweep the thread.
Remaining length of needle thread is too short.
Position of the wiper is improper.
Air pressure is decreased, suction force is decreased and
thread is not sucked.
Air pressure is decreased and thread is not sucked since
dust bag clogs with too much thread waste.
When remaining amount (thread take-up lever) of needle
thread after completion of needle thread clamp is small,
bobbin thread is brought to the position above the cloth at
the first stitch of the start of sewing.
Knife built in the cloth presser has become dull.
Needle thread holding is weak and thread on the needle
thread holding side is drawn out at the time of needle thread
trimming. As a result, remaining length of needle thread is
lengthened.
Rough motion of needle thread occurs at the time of
thread trimming and knife misses needle thread and does
not trim it.
Thread is swept with the wiper and brought to the suction
port. However, needle thread is too short and comes off
the wiper on the way or fails to be sucked.
Air consumption in the factory is increased and the
pressure is decreased.
Clamping force is decreased due to the decrease of air
pressure.
Decrease the stroke of thread take-up spring.
(When decreasing the stroke, be careful of the isolated idling
loops.
Adjust the needle thread draw-out unit so that the needle thread
draw-out amount is reduced.
Adjust the length of remaining thread so that the length of needle
thread after thread trimming is adjusted to approximately 15
mm of suction amount.
Place the wiper at the proper position.
Adjust to the standard pressure, 0.6MPa.
Install more air compressors.
Remove thread waste or the like in the dust bag.
Adjust the needle thread draw-out unit to increase the needle
thread draw-out amount.
Perform thread tension release at the start of sewing. (Function
setting No. 100)
Make needle thread draw-out motion again after needle thread
clamping. (Function setting No.18 : 2.)
Make function both function setting No. 100 and No. 18 : 2.
Replace the needle thread trimming knife.
Adjust air pressure to 0.6MPa.
Trouble Cause 1 Cause 2 Corrective measure and
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