5. TROUBLESHOOTING
108
5-5. Uneven seams (3) ……Seam lifts up at the sewing start
Seam lifts up and does not tighten at the sewing start
Cause
Check
Remedy
Page
Upper thread scissors
gradual opening timing
Adjust the timing so that the upper thread scissors
gradually start opening when the feed mechanism
moves about 1.5 - 2.5 mm.
94
Upper thread
scissors
Upper thread scissors
operation
Apply grease to the inclined face of the opening
cam.
94
Upper thread feeding Thread take-up amount
Loosen the screw to decrease thread take-up
amount so that upper thread does not pull out of
scissors assembly at the sewing start.
101
5-6. Uneven seams (4) …… Uneven sewing pitch at the sewing start
Bird’s nests form at the sewing start, and after 5 – 6 mm the sewing pitch suddenly increases
Cause
Check
Remedy
Page
Lower thread clamp
Lower
thread
clamp
opening timing
Advance the timing at which the lower thread clamp
starts to open.
97
5-7. Uneven seams (5)……Poor rounding of seam
Cause
Check
Remedy
Page
Zigzag thread upper
thread tension
Adjust the upper thread tension appropriately.
Instruction
manual
Zigzag tension disc
opening
⋅
Check the opening of the zigzag tension discs.
⋅
Replace the tension release solenoid.
100
Thread tension
Lower thread tension
Adjust the lower thread tension appropriately.
Instruction
manual
Upper thread threading
Thread the upper thread correctly.
Instruction
manual
Threading
Lower thread threading
Thread the lower thread correctly.
Instruction
manual
Stitch patterns
Purl stitch, whip stitch
Set using parameter number 11.
Instruction
manual
Tension release
Tension release timing
Use parameter numbers 63 to 66 to change the
tension release on and off timing.
Instruction
manual
5-8. Uneven seams (6) …… Around rear tack or front tack
Cause
Check
Remedy
Page
Tension release
Tension release timing
Use parameter numbers 63 to 66 to change the
tension release on and off timing.
Instruction
manual
Upper thread threading
Thread the upper thread correctly.
Instruction
manual
Threading
Lower thread threading
Thread the lower thread correctly.
Instruction
manual
Zigzag thread
tension
Zigzag tension disc
opening
⋅
Adjust the tension disc opening amount.
⋅
Check the opening of the zigzag tension discs.
⋅
Replace the tension release solenoid.
100
Upper thread
scissors
Upper thread scissors
operation
Apply grease to the inclined face of the opening
cam.
94
4000Q
Screw
Increase
Decrease