Troubles And Corrective Measures - JUKI DSC-245 Instruction Manual

29.TROUBLES AND CORRECTIVE MEASURES

Trouble
① The thread path,needle point,hook point or bobbin
1. Thread breakage
(Thread frays or case positioning finger has scratches.
② The needle thread tension is too high.
wears out.)
③ The needle hits the hook point.
④ Lubrication to hook is inadequate.
⑤ The needle thread tension is too low.
(Needle thread
⑥ The thread take-up spring has an excessively high
remains 2 to 3 cm on
the wrong side of the
tension while it has an excessively small stroke.
cloth.)
⑦ The timing between the needle and hook is too
early or late.
⑧ The bobbin races frequently.
① The clearance between the needle and the hook
2. Stitch skipping
point 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 correct.
⑤ The size of the needle is wrong.
⑥ A synthetic fiber thread or thin thread is used.
① The thread has not been passed through the notch
3. Loose stitches
of the bobbin case tension spring.
② The thread path is poorly finished.
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.
① The bobbin thread is too short.
4. A few stitches are
② The bobbin thread breaks.
skipped.
③ A nylon thread is used when sewing lightweight
material.
① The tension of the auxiliary thread tension
5. The thread slips off
② Thread take-up timing is too early.
③ Returning force of the thread take-up spring is
excessively strong.
④ The feed dog and walking foot trims thread.
⑤ Actuating quantity of the picker is inadequate.
① The last stitch has been skipped.(The clearance
6. The needle thread
cannot be trimmed. between the needle and the hook is too large.)
(The bobbin thread
can be trimmed.)
① The thread trimming timing is wrong.
7. Both needle and bob-
② The knife has been damaged.
bin threads cannot be
trimmed.
③ The knife pressure is inadequate.
④ The movement of the rotary knife is short.
⑤ The thread trimming solenoid fails to work.
① The thread trimming timing is wrong.
8. Thread cannot be
② The knife pressure is inadequate.
trimmed sharply.
③ The knife blade is blunt.
① Breakage due to thread frayed caused by standing
9. Chain off thread
doesn't come out. and flapping of thread.
② Breakage between the bottom face of the presser
foot and the contact face with throat plate.
① The presser foot slips when riding on the stepped
10. Stepped part is
clogged. part.
① Sewing speed is too fast,resulting in reducing the
11. When the alternate lift
is increased,the pitch feed force.
cannot be achieved
as per the scale.
Cause
– 19 –
Corrective measures
○ Remove the scratches on the hook point using a fine sand
paper. Buff the bobbin case positioning finger.
○ Properly adjust the needle thread tension.
○ See "17.NEEDLE-TO-HOOK RELATIONSHIP".
○ Properly adjust the lubrication. See "4.LUBRICATION".
○ Properly adjust the needle thread tension.
○ Decrease the tension,and increase the stroke.
○ See "17.NEEDLE-TO-HOOK RELATIONSHIP".
○ Increase the spring pressure. Alternatively,reduce the
thread trimming speed.
○ See "17.NEEDLE-TO-HOOK RELATIONSHIP".
○ See "17.NEEDLE-TO-HOOK RELATIONSHIP".
○ Increase the presser foot pressure.
○ See "17.NEEDLE-TO-HOOK RELATIONSHIP".
○ Replace the needle by one which is one
grade thicker.
○ Wind the thread round the needle as illustrat-
ed.
○ Properly thread the bobbin case.
○ Grind it using a fine sand paper or a buff.
○ Replace the bobbin or hook.
○ Properly adjust the tension.
○ Properly adjust the needle thread tension.
○ Slightly reduce the sewing speed.(2,000 sti/min)
○ Use a ball-point needle..
○ Replace the bobbin by a standard one (aluminum).
○ Decrease the bobbin thread tension and the thread trim-
ming speed.
○ Use the soft start function.
○ Decrease the tension.
○ See "21.ADJUSTING THE THREAD TRIMMING CAM".
○ See "9.THREAD THE MACHINE HEAD". Replace the
thread guide with an appropriate one.
○ Replace the walking foot with an appropriate one.
○ See "24.ADJUSTING THE OPERATING STROKE OF
THE PICKER".
○ See "17.NEEDLE-TO-HOOK RELATIONSHIP".
○ See "21.ADJUSTING THE THREAD TRIMMING TIMING".
○ Replace the knife.
○ Increase the knife pressure.
○ See "23.ADJUSTING MAX. MOVING POSITION OF THE
ROTARY KNIFE".
○ Check the motor solenoid for proper operation.
○ See "22.ADJUSTING THE THREAD TRIMMING TIMING".
○ Increase the knife pressure.
○ Replace the knife.
○ Use the furnished thread guide and the presser foot with a
slot.
○ Use B15242450AB presser foot (option) and B147024500B
walking foot (option).
○ Reduce the sewing speed.