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Problem
11. Incorrect thread trimming
(upper thread or lower
thread is not being
trimmed). (B772A)
12. Broken needles
13. The thread wiper does
not wipe the thread.
(B772A-403, -903)
14. Material does not cut
properly.
¡ Is the needle properly installed?
If it is incorrect, install the needle correctly.
¡ Is the fixed knife or movable knife blunt?
Replace the fixed knife or the movable knife.
¡ Is the material being pushed or pulled with excessive force during
sewing?
¡ Is the needle properly installed?
If it is incorrect, install the needle correctly.
¡ Is the needle bent, is the needle tip broken, or is the needle hole
blocked?
Replace the needle.
¡ Is the needle and rotary hook timing incorrect?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the rotary hook.
¡ Is the needle timing advanced too far with respect to the feed dog?
Retard the needle timing.
Caution
¡
It is extremely dangerous to leave any pieces of broken needle
sticking in the material. If the needle breaks, search for all pieces
until the whole of the needle is found again.
¡
Furthermore, we recommend that through steps be taken to ac-
count for such needles to comply with product liability regula-
tions.
0469M
¡ Is the length of thread trailing from the needle hole too short after
thread trimming?
Adjust the pretension.
¡ Is there no clearance between the upper knife and the needle plate
knife?
Adjust the left-right position of the upper knife.
¡ Is the upper knife raised too high?
Adjust the vertical position of the upper knife.
¡ Is the cutting blade of the upper knife worn?
Replace the upper knife.
Possible cause
DB2-B771A, B772A
15. TROUBLESHOOTING
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