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12. TROUBLESHOOTING
12. FEHLERSUCHE
12. RESOLUTION DES PROBLEMES
12. LOCALIZACION DE AVERIAS
Problem
3. Thread breaks
0471M
4. Thread does not
tighten, or tightening
is uneven
Needle thread
Looper thread
0472M
77
• Is the thread tension too strong?
Adjust the thread tension.
• Is the thread being used one which breaks easily?
Reduce the sewing speed.
Adjust the thread tension so that it is as weak as possible.
• Is the needle hole too narrow compared with the thread?
Replace the needle with a needle that is one rank thicker.
• Is the correct kind of needle being used?
Replace with the correct kind of needle.
• Are the needle and looper installed in the correct positions?
Adjust the height of the needle bar and the position of the looper.
• Are the positions of each of the thread paths correct?
Check the positions of each thread path.
• Is the needle, looper, retainer, needle plate, presser foot needle hole or a
part of the thread path broken?
If a part is a damaged, smooth it with an oiled grindstone or replace the
broken part.
• Is the thread breaking due to heat because the needle is becoming hot?
Use the needle thread cooler.
[If the silicone oil does not provide sufficient cooling, use of a pneu-
matic-type needle cooler (option) is recommended.]
Reduce the sewing speed.
• Is the position of the needle guard correct?
Adjust the position of the needle guard.
• Is the thread of an uneven thickness?
Use good-quality thread.
• Is the needle hole too narrow compared with the thread?
Replace the needle with a needle that is one rank thicker.
• Do the thread tension discs operate smoothly?
Clean away any rubbish from between the thread tension discs so that
they operate smoothly.
• Are the positions of each of the thread paths correct?
Check the positions of each thread path.
• Are the threads not running smoothly along the thread paths?
Smooth the thread paths using a fine-grade file.
• Are the needle and looper installed in the correct positions?
Adjust the height of the needle bar and the position of the looper.
• Is the position of the needle guard correct?
Adjust the position of the needle guard.
Possible cause
DT3-B291
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