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4
Causes of Troubles and Troubleshooting
1) Sewing machine troubleshooting
No
Symptom
Direction and height of
needle
Needle
Timing of feed dog
Needle breaks
1
Ascending level of
needle bar
Height of needle
Gap between needle
and hook
Threading method
Needle
Direction and height of
needle
2
Thread cuts
Upper thread tension
Lower thread tension
Working capacity of
take-up lever spring
Thread tension
Poor thread
Thread take up spring
3
adjustment
tension
Gap between opener
and hook
Direction and height of
needle
Needle
Threading
Gap between the
Upper thread
needle and the hook
falls out when
Remaining upper
4
starting to sew
thread length after
or sewing is
trimming
skipped
Lower thread holder
Check the up-stop
position of the needle
Checkpoints
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 tight lower thread tension
Too big take-up lever
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 the end of the needle is
broken
Wrong direction
The timing between the needle and
hook is bad
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
Root cause
Reinsert the needle correctly
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
Change the needle
Insert the thread in the right way
Adjust the timing between the needle
and 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
Corrective action
29
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