Brother Z-8550B Instruction Manual page 147

Problem
Incorrect thread trimming
(Upper and lower threads
are both not being
trimmed)
Incorrect thread trimming
(Upper thread is not being
trimmed.)
(Lower thread is not being
trimmed.)
The thread wiper does not
wipe the thread.
Oil gauge (1) is not visible
in oil gauge window.
Machine does not operate
at high speed.
Possible cause
• Is the needle tip bent? Is the needle tip broken, or is
the needle hole blocked?
Replace the needle.
• Is the needle and rotary hook timing correct?
Adjust the height of the needle bar.
Adjust the clearance between the needle and the tip
1
of the rotary hook.
NOTE
• 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 thorough steps be
taken to account for such needles to comply with
product liability regulations.
(Z-8560B)
• Is the fixed knife or movable knife damaged or worn?
Replace the fixed knife or the movable knife.
(Z-8560B)
• Is the thread trimming timing incorrect?
Adjust the rotating direction of the thread trimming
1
cam.
(Z-8560B)
• Is the needle properly installed?
If it is incorrect, install the needle correctly.
(Z-8560B)
• Is the fixed knife or movable knife blunt?
Replace the fixed knife or the movable knife.
(Z-8560B)
• Do skipped stitches occur during sewing?
(Z-8560B)
• Is the length of thread trailing from the needle hole
too long after thread trimming?
Adjust the upper thread feeding device.
• Is the oil tank empty?
Fill the oil tank with oil.
• Is the sewing speed setting or backtack stitch speed
setting too slow?
Use the sewing speed key to set the high speed.
Page
See Adjusting the height of
the needle bar on
1
page 111.
See Adjusting the needle
and rotary hook timing on
page 112.
See Replacing the fixed
knife and movable knife on
page 98.
1
See Adjusting the thread
trimming cam position on
page 119.
See Installing the needle
on page 17.
See Replacing the fixed
knife and movable knife on
page 98.
1
See Skipped stitches occur
while sewing
See Adjusting the upper
thread trailing length after
thread trimming on
page 122.
1
See Lubrication on page 9.
See Name and function of
each operation panel item
on page 24.
134