Brother LK3-B484 Owner's Manual

ZE-8570,8580

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Upper
thread

Upper
thread

Lower
thread

5. Skipped stitches at sewing

start

Thread unravelling at
sewing start

• Are the thread take-up spring tensions too strong?

Reduce the tension of the thread take-up springs.

• Is the thread tension spring operating range too large?

Lower the position of the thread tension spring.

• Is the needle too wide?

Try using a needle with a count that is one lower than the cur-
rent needle.

<ZE-8570>
• Is the needle bar at the needle up stop position at the sewing

start?
Set the needle bar to the needle up stop position at the sewing
start.

• Is the length of the upper thread trailing from the needle hole

too short?
Pull about 50 mm of thread through the needle hole at the sew-
ing start.

<ZE-8580>
• Is the trailing length of the upper thread too short after thread

trimming?
Adjust the upper thread feeding device.

• Are the threads not being trimmed cleanly?

Sharpen the fixed knife with a whetstone, or replace the fixed
knife.
Replace the movable knife.

• Is the length of thread trailing out from the bobbin case after

thread trimming too short?
If the bobbin is spinning loosely, replace the bobbin tension
spring in the bobbin case.
Adjust the tension of the lower thread presser spring.

• Is the needle up stop position too high?

Adjuste the synchronizer.

6. Uneven seam

• Is the presser foot pressure too weak?

Adjuste the presser foot pressure.

• Is the feed dog too low?

Adjust the feed dog height.

• Is the bobbin scratched?

If the bobbin is damaged, smooth it with an oiled grindstone or
replace it.

7. Horizontal thread tightening

not balanced

• Is the upper thread tension or lower thread tension too strong

or to weak?
Adjust the upper thread tension or lower thread tension.

• Does the rotary disc rotate smoothly?

Adjust the pre-tension.

• Is the tension of the thread take-up spring correct?

Adjust the tension of the thread take-up spring.

• Is the stroke of the thread take-up spring correct?

Adjust the position of the thread take-up spring.

• Is the needle and rotary hook timing correct?

Adjust the needle and rotary hook timing.

• Is the needle and rotary hook timing correct?

Adjust the height of the needle bar.
Adjust the distance between the needle and the tip of the rotary
hook.

• Is the thread too thick for the needle?

Use the correct needle or the correct thread.

• Is the rotary hook, bobbin case, thread take-up lever or some

other part in the thread path damaged?
Repair the damage, or replace the part with a new one.