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140401
27. MOTOR PULLEY AND SEWING SPEED
(This item is only applicable to the DSU-142)
1) Use a 3-phase 400 W AC clutch motor.
2) Use an M type V-belt.
3) The relation among the motor pulley, the sewing speed of sewing machine is as shown in the table below:
Model
Sewing speed
DSU-142
2,000 sti/min
(Caution) The effective diameter of motor pulley is obtained by subtracting 5 mm from its outside diameter.
28. TROUBLES AND CORRECTIVE MEASURES
Trouble
1. Thread breakage.
(Thread frays or
wears out.)
(Needle thread remains
2 to 3 cm on the wrong
side of the cloth.)
2. Stitch skipping
3. Loosen stitches
Effective diameter of
handwheel
φ 76.0
Causes
① The thread path, needle point, hook point or
bobbin case positioning finger has scratch-
es.
② The needle thread tension is too high.
③ The needle hits the hook point.
④ The needle thread tension is too low.
⑤ The thread take-up spring has an excessive-
ly high tension while it has an excessively
small stroke.
⑥ The timing between the needle and hook is
too early or late.
⑦ The bobbin races frequently. (For the DSU-
142-7)
① The clearance between the needle and the
hook pint is too large.
② The timing between the needle and the hook
point is too early or late.
③ The presser foot pressure is too low.
④ The clearance between the top edge of the
needle eyelet and the hook point is not cor-
rect.
⑤ The size of the needle is wrong.
⑥ A synthetic fiber thread or thin thread is
used.
⑦ A heavy-weight material is being sewn.
① The bobbin thread has not been passed
under the tension spring of the bobbin case.
② The presser foot or the thread path of the
needle hole in the throat plate has scratches.
③ The bobbin does not rotate smoothly.
④ The bobbin thread tension is too low.
⑤ The bobbin thread has been wound too tight.
⑥ An untwisted synthetic thread is used.
⑦ A coated cloth or nylon yarn is used.
Number of poles
Frequency
of motor
50Hz
4
60Hz
○ Remove the scratches on the hook point using
○ Properly adjust the needle thread tension.
○ Refer to the chapter on "18. NEEDLE-TO-
○ Properly adjust the needle thread tension.
○ Decrease the tension, and increase the stroke.
○ Refer to the chapter on "18. NEEDLE-TO-
○ Increase the idling prevention spring pressure.
○ Refer to the chapter on "18. NEEDLE-TO-
○ Refer to the chapter on "18. NEEDLE-TO-
○ Increase the presser foot pressure.
○ Refer to the chapter on "18.
○ Replace the needle by one
○ Wind the thread round the nee-
○ Adjust the timing of the needle
○ Properly thread the bobbin case.
○ Replace the bobbin or the bobbin case.
○ Increase the bobbin thread tension.
○ Too high the tension of the bobbin thread wind-
○ Decrease the tension of the bobbin thread
○ Slightly reduce the sewing speed (1,800 sti/min)
○ Use a ball-point needle.
– 16 –
Number of
Effective diameter of
revolution of motor
1,430 rpm
1,715 rpm
Corrective measures
a fine sand paper. Buff the bobbin case posi-
tioning finger.
HOOK RELATIONSHIP".
HOOK RELATIONSHIP".
HOOK RELATIONSHIP".
HOOK RELATIONSHIP".
NEEDLE-TO-HOOK RELA-
TIONSHIP".
which is one grade thicker.
dle as illustrated.
and the hook to 2.8 mm, 1.1 mm.
ing tension.
winding tension.
motor pulley
φ 105
φ 90
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