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1-13. Troubles and corrective measures (Sewing conditions)
Trouble
Cause
Corrective measures
Page
1. The needle
thread slips off at
the start of bar-
tacking.
1
Stitches are slipped at the start.
™
Adjust the clearance between the needle
and the shuttle to 0.05 to 0.1 mm.
114
™
Set soft-start sewing at the start of
bartacking.
98
2
The needle thread remaining on
the needle after thread trimming
is too short.
™
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.
19
3
The bobbin thread is too short.
™
Decrease the tension of the bobbin
thread.
17
™
Increase the clearance between the
needle hole guide and the counter knife.
116
4
Needle thread tension at 1st
stitch is too high.
™
Decrease the tension at 1st stitch.
5
T h r e a d c l a m p i s u n s t a b l e
(material is apt to be expanded,
thread is hard to slide, thread is
thick, etc.).
™
Decrease the number of rotation at 1st
stitch at the sewing start. (Extent of 600
to 1,000 rpm)
™
Increase the number of stitches of
thread clamp to 3 to 4 stitches.
6
Pitch at 1st stitch is too small.
™
Make the pitch at 1st stitch longer.
™
Decrease the needle thread tension at
1st stitch.
2. Thread often
breaks or
synthetic fiber
thread splits
finely.
1
The shuttle or the driver has
scratches.
™
Take it out and remove the scratches
using a fine whetstone or buff.
2
The needle hole guide has
scratches.
™
Buff or replace it.
3
The needle strikes the work
clamp foot.
™
Correct the position of the work clamp
foot.
18
4
Fibrous dust is in the groove of
the shuttle race.
™
Take out the shuttle and remove the
fibrous dust from the shuttle race.
5
The needle thread tension is too
high.
™
Reduce the needle thread tension.
17
6
The tension of the thread take-up
spring is too high.
™
Reduce the tension.
19
7
The synthetic fiber thread melts
due to heat generated on the
needle.
™
Use silicone oil.
124
8
When taking up thread, thread is
pierced with needle tip.
™
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.
3. The needle often
breaks.
1
The needle is bent.
™
Replace the bent needle.
15
2
The needle hits the work clamp
foot.
™
Correct the position of the work clamp
foot.
18
3
The needle is too thin for the
material.
™
Replace it with a thicker needle according
to the material.
4
The driver excessively bends the
needle.
™
Correctly position the needle and the
shuttle.
114
4.Threads are not
trimmed.
1
The counter knife is dull.
™
Replace the counter knife.
2
The difference in level between
the needle hole guide and the
counter knife is not enough.
™
Increase the bend of the counter knife.
3
The moving knife has been
improperly positioned.
™
Correct the position of the moving knife.
116
(Bobbin thread only)
4
The last stitch is skipped.
™
Correct the timing between the needle
and the shuttle.
114
5
Bobbin thread tension is too low.
™
In crease the bobbin thread tension.
6
Flopping of cloth
™
Lower the intermediate presser height of
the last stitch.
