SunStar KM-380BL, User Manual

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4
Causes of Trouble and Troubleshooting
1) Sewing machine troubleshooting
No Symptom Checkpoints Root cause Corrective action
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Needle breaks
Thread breaks
Poor thread
adjustment
Upper thread
falls out when
starting to sew
or sewing is
skipped
Trimming miss
Reinsert the needle correctly and
place closely it to its highest position
Change the needle
Adjust the timing of feed dog
Adjust the timing of needle and hook
Adjust the timing of needle and hook
Adjust the timing of needle and hook
Thread the needle correctly
Change the needle
Insert the needle correctly
Reduce tension of upper thread
Reduce tension of lower thread
Adjust take-up lever spring
Adjust the upper and lower thread
tensions
Adjust the thread take up spring
tension
Adjust the gap between the opener
and hook
Reinsert the needle correctly and
push in to its highest level
Change the needle
Insert the thread in the right way
Adjust the timing of the needle and
the hook
Increase the adjustment volume of
the upper thread on the control box
Adjust the location and tension of the
lower thread holder
Readjust the needle’s up-stop film
position
Readjust the movable knife setting
position
Correct the tension adjustment and
surface contact of movable and fixed
knives
Needle is inserted into wrong position
Needle is bent
Bad timing of feed dog
Bad timing of needle and hook
Bad timing of needle and hook
Bad timing of needle and hook
Wrong threading
Bent needle or broken needle tip
Needle inserted in the wrong position
Too tight upper thread tension
Too loose lower thread tension
Loose upper thread
Upper and lower thread tensions are
bad
Thread take up spring tension is
inadequate
The gap between the opener and
hook is inadequate
Needle is inserted into wrong position
Needle is bent
Wrong direction
Bad timing of needle and hook
The length of the remaining upper
thread is too short
After trimming, lower thread holder
does not hold the lower thread
Due to problems in the up-stop
position of the needle, the thread take
up lever pulls the upper thread out of
the needle when the sewing starts
The height and distance between the
movable knife and the hook do not
match
Tension and contact of movable and
fixed knives are bad
Direction and height of
needle
Needle
Timing of feed dog
Ascending level of
needle bar
Height of needle
Gap between needle
and hook
Threading method
Needle
Direction and height of
needle
Upper thread tension
Lower thread tension
Working capacity of
take-up lever spring
Thread tension
Thread take up spring
tension
Gap between opener
and hook
Direction and height of
needle
Needle
Threading
Gap between the
needle and the hook
Remaining upper
thread length after
trimming
Lower thread holder
Check the up-stop
position of the needle
The gap between the
movable knife and the
hook
Check the tension of
fixed knife