Phenomena, Causes And Corrective Measures Of Troubles In Sewing - JUKI MOL-254N Instruction Manual

IX. PHENOMENA, CAUSES AND CORRECTIVE MEASURES
OF TROUBLES IN SEWING
No. Phenomenon
1 Thread slips off the
needle eyelet at the
start of sewing.
2 Thread breakage oc-
curs many times.
3 Needle breakage oc-
curs many times.
Cause
① Stitches skip at the start of sew-
ing.
② Length of needle thread remain-
ing at the needle after thread
trimming is short.
③ Bobbin thread is short.
① Hook or driver has a scratch.
② Finish of needle eyelet is not
good.
③ Presser foot comes in contact
with needle.
④ Shuttle groove is clogged with
thread waste.
⑤ Needle thread tension is too
high.
⑥ Thread take-up spring pressure
is too strong.
⑦ Arm thread guide has a scratch.
⑧ Thread is weak.
① Needle is bent.
② Presser foot comes in contact
with needle.
③ Needle is too thin.
④ Needle is excessively bent by
driver.
– 59 –
Corrective measure
Make a clearance of 0.05 to 0.1 mm
between needle and hook.
Delay the sewing speed at the start
of sewing.
Decrease tension of the thread
tension No. 1.
Increase tension of the thread take-
up spring.
Decrease stroke of thread take-up
spring.
Decrease tension of the bobbin
thread.
Adjust the disk rising timing.
Remove the part and polish it with a
fine grind stone or buff.
Replace the needle with a new one.
Adjust position of the presser foot.
Remove the thread waste.
Decrease tension of the needle
thread.
Decrease tension of the thread
take-up spring.
Polish it with buff or replace it with a
new one.
Delay the sewing speed.
Replace the needle with a new one.
Adjust position of the presser foot.
Change the needle No. in accor-
dance with sewing products.
Adjust the position of the needle
and driver.