4
Cause of trouble and troubleshooting
37
1) Machine troubleshooting
No
Symptom
Checkpoints
Root cause
Corrective action
Direction and height
of needle
Needle
Feed dog timing
Gap between needle
and hook
Threading method
Needle
Direction and height
of needle
Upper thread tension
Lower thread tension
Thread take up stroke
Hook
Feed dog
Needle plate
Thread tension
Thread take up spring
tension
Gap between opener
and hook
Direction and height
of needle
Needle
Threading
Hook timing
Gap between the
needle and the hook
Needle breaks
Thread breaks
Poor thread
adjustment
Upper thread
falls out when
starting to sew
or sewing is
skipped.
1
2
3
4
Needle is inserted into wrong
position
Needle is bent
Bad timing of feed dog
Bad timing of needle and hook
The heads of the needle and the
hook interfere each other.
Wrong threading (inserted from the
opposite side)
Bent needle
Needle inserted in the wrong
direction and height
Too tight upper thread tension
Too tight lower thread tension
Too large stroke
There is a scratch on the hook
edge
There is a scratch on the needle
hole of the feed dog
There is a scratch on the thread
case and around the needle plate
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
Bent needle
Wrong direction
The timing between the needle and
hook is bad
Needle and hook are too far apart
Reinsert the needle correctly and
push in to its highest level.
Change the needle
Adjust the timing of feed dog
Adjust the timing of needle and
hook
Adjust the location of the hook
Thread the needle correctly
Change the needle
Insert the needle correctly
Reduce the tension of upper thread
Reduce the tension of lower thread
Adjust the stroke level
Remove the scratch on the hook
edge
Remove the scratch on the feed
dog
Remove the scratch on the needle
plate.
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 up to its highest level.
Change the needle
Insert the thread in the right way.
Adjust the timing between the
needle and hook
Adjust the position of the hook