SunStar KM-857 Series User Manual page 36

No Symptom
Remaining upper
thread length after
trimming
Lower thread holder
Upper thread
falls out when
4 starting to sew
Check the up-stop
or sewing is
position of the needle
skipped.
Check the oil felt
tension of upper
thread
The gap between the
movable knife and
the hook
Check the tension of
fixed knife
5 Trimming miss Direction of the needle
Blade side of movable
and fixed knives
Trimming cam timing
Thread release stroke
Trimming timing
Opening of the thread
tension adjusting plate
Tension of auxiliary
thread tension
Too short
6 thread length adjustment assembly
after trimming
Thread take up stroke
Thread release
adjustment volume
on the control box
36
Checkpoints
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 upper thread oil felt is pressing
the thread too strongly.
The height and distance between
the movable knife and the hook do
not match
Tension and contact of movable
and fixed knives are bad
Needle is not inserted correctly
Scratch and abrasion of movable
and fixed knives
The timing of trimming cam is
wrong
Thread release stroke is too small
Wrong trimming timing
The opening on the thread tension
control plate is too small
Too strong tension on the auxiliary
thread tension control assembly
Thread take up stroke is too large
Volume is adjusted to too low
Root cause
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
Adjust the felt tension
Readjust the movable knife setting
position
Correct the tension adjustment and
surface contact of movable and
fixed knives.
Insert the needle correctly
Replace movable knife or fixed
knife.
Adjust the timing of trimming cam
Readjust the thread release stroke
Adjust the trimming timing
Adjust the thread release stroke
Adjust the tension of the auxiliary
thread tension control assembly
Adjust the thread take up spring's
stroke
Increase the volume adjustment.
Corrective action