28
4
Causes of Trouble and Troubleshooting
1) Sewing machine troubleshooting
No
Symptom
Checkpoints
Root cause
Corrective action
1
2
3
4
5
6
Needle breaks
Thread breaks
Sewing is
skipped
Upper thread
does not wind
Lower thread
does not wind
Trimming miss
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
Reinsert the needle correctly and
push in to its highest level
Change the needle
Insert the thread in the right way
Adjust the timing between the needle
and hook
Adjust the timing between the needle
and hook
Adjust the timing between the needle
and hook
Change Idle-operation prevention
spring
Control the stroke of Thread take up
spring
Reduce the tension of upper thread
Enhance the tension of lower thread
Enhance the tension of upper thread
Reduce the tension of lower thread
Match the tension between the
movable knife and the hook
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
Needle is inserted into wrong
direction
Needle is bent
Wrong direction
The timing between the needle and
hook is bad
The timing between the needle and
hook is bad
Needle and hook head are too far
apart
The length of the remaining upper
thread is too short
When trimming, bobbin runs idly. So
the upper thread is too short to go
up.
It is not strong to raise the lower
thread
Too tight upper thread tension
Too weak lower thread tension
Too weak upper thread tension
Too tight lower thread tension
The tension between the movable
knife and the hook do not match
Direction and height of
needle
Needle
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
Direction and height of
needle bar
Needle
Threading
Ascending level of
needle bar
Height of needle bar
Gap between the
needle and the hook
Bobbin case Idle-
operation prevention
spring
Thread take up spring
Check tension of fixed
knife
