Corrective Measures For Stitching Troubles; Thread Breakage; Thread Remaining And/Or Poor Tightness Of Stitches - JUKI MB-373 Manual

5. CORRECTIVE MEASURES FOR STITCHING TROUBLES

(1) Thread breakage

1) The looper hooks thread twice due to improper lengthwise positioning of the yoke slide.
™ Move the loop positioning finger cam back and forth to make readjustment so that the blade point of the
looper passes through the center of the thread triangle at the 9th or 10th stitch.
2) The tension of the tension disc No. 1 is too high.
™ Decrease the tension to approx. 7 to 15 g.
3) The floating timing of the tension disc No. 2 is too late.
™ For adjusting the height of the needle bar, refer to the table of (5) The floating timing of the tension disc
No. 2, p.6.
4) The crosswise travel timing of the yoke slide is not correct.
™ For adjusting the height of the needle bar, refer to the table of (3) Timing the travel of the yoke slide, p.4.
5) The looper catches thread twice due to an incorrect lengthwise travel timing of the yoke slide.
™ Correct the timing so that the yoke slide begins to go back immediately after the blade point of the looper
has passed through the thread triangle.

(2) Thread remaining and/or poor tightness of stitches

(The thread remaining means that the thread of an ending stitch is trailed or left 5 to 10 mm from
the knot.)
1) The tension of the tension disc No.1 is insufficient.
™ Increase the tension to approx. 7 to 15 g.
2) The tension disc No. 2 floats too early.
™ For adjusting the height of the needle bar, refer to the table of (5) The floating timing of the tension disc
No. 2, p.6.
3) The crosswise travel timing of the yoke slide is bad.
™ For adjusting the height of the needle bar, refer to the table of (3) Timing the travel of the yoke slide, p.4.
4) The positon of needle entry into a button hole is not correct.
™ Correct the position of needle entry so that the needle comes down slightly behind the center of a button
hole, preventing the needle front from touching the button hole.
5) The amount of the lift of the button clamp jaw lever is not enough.
™ Readjust the lift to 9 mm.
(Corrective measure against thread remaining)
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Needle entry position