Bad Sewing Condition & Its Cause And Remedy - Mitsubishi PLK-E03BT Technical Manual

9. BAD SEWING CONDITION & ITS CAUSE AND REMEDY
[NOTE] Please fix the troubles during the sewing machine operation with referring to the
following instructions.
Beside, if the trouble conditions are not coming under these classification, please
contact the sewing machine dealers nearby.
Bad condition
1.
Upper thread
breakage often
happens
Needle and shuttle hook are not
Thread melts with needle heat
Thread take up spring swings too
Upper thread is broken before
Needle size is bigger than thread
2.
Upper thread
is pulled out
from needle
Thread guide is in wrong position
Needle and shuttle hook are in
Bobbin thread tension is too tight
3.
Skip stitch
happens at
Thread tail from needle is very
start sewing
Thread tail from needle is very
Cause
Poor thread quality
Tight upper thread tension
Strong thread take up spring
Upper thread is thicker than
needle size
Damages on shuttle hook or
driver
Damages inside presser foot
needle hole
in proper timing
Thread tension discs are not
opened at trimming
much
regular trimming
size
Pre-tension is too tight
bad timing
Trimmer timing is not correct
Too short bobbin thread by
bobbin spinning at trimming
short after trimming
short after trimming
Remedy
Use better quality thread
Adjust thread tension
Adjust thread take up spring
properly
Change needle to suitable
Change them new ones or
grind them with buffing wheel
or grind stone
Change it new one or grind it
with buffing wheel
Adjust the timing
Slow down sewing speed
Use silicon oil
Use needle cooler
Adjust thread tension release
Adjust thread take up spring's
swing stroke
Adjust fixed knife and needle
plate position
Change needle to suitable
Adjust pre-tension
Adjust thread guide position
properly
Adjust the position properly
Adjust trimmer cam position
Adjust movable knife position
Adjust synchronizer position
Use non racing spring with
bobbin
Loosen bobbin thread tension
spring
Decrease pre-tension
Adjust trimmer cam position
Adjust synchronizer position
Make thread take up swing
stroke smaller
Advance thread tension
release timing
Adjust thread guide position
properly
Decrease pre-tension
－37－
Ref. page
size
size
Control unit
& Item
----
6-3
7-13
----
----
----
----
6-2(5)
----
----
7-16
7-12
7-11
----
7-14
7-5
7-2
7-9
7-10
7-17
----
6-3(1)
7-14
7-9
7-17
7-12
7-5
7-2