| Needle
Thread Breakage |
| Cause
|
Remedy |
| Misaligned
offwinding from thread package. |
Ensure
overhead guide is directly above cop stand pin, at 2 1/2 times
the height of the thread package. Use foam pad or similar to
prevent package tilting. |
| Trapping at package base. |
Reduce thread stand height to prevent vibration
and spillage. Use foam pad to prevent trapping after spillage. |
| Thread trapped at thread guide. |
Can occur after thread breaks. Rethread correctly.
|
| Snarling
before tension disc. |
Increase
wraps on pre-tension thread guides and reduce disc tension.
Ensure discs are smooth. |
| Excessive
tension. |
Use stronger
thread of adjust tension (using Coats Tension Meter). |
| Broken
checkspring. |
Replace
and adjust. |
| Sharp
edges on throat plate, hook point, needle guard, bobbin case,
needle groove or eye. |
Polish
rough edges, replace if necessary. Replace needle with one of
better quality. |
| Thread
fraying at needle. |
Use finer
thread or coarser needle, as appropriate. |
| Excessive
needle heat; groove or eye blocked with melted fabric. |
Improve
fabric finish. Change to better needle, style and finish. Apply
needle lubricant via thread. Use needle cooler etc |
| Hook
overheating. |
Ensure
adequate oil supply. Check needle to hook clearance. |
| Poor
quality thread. |
Change
to better quality, correctly finished thread. |
| |
| Bobbin
or Looper Thread Breakage |
| Cause
|
Remedy |
| Badly
wound thread on bobbin. |
Adjust
bobbin winder alignment. Use prewound bobbins. |
| Tension
too tight or bobbin over-running. |
Adjust
bobbin case tension (using Coats Tension Meter). Insert washer
or spring to prevent over-running. |
| Sharp
edges on bobbin case or spring or looper eyelet. |
Polish
edges and contact surfaces. |
| Bobbin
case not fitting correctly. |
Check size
/ type of bobbin. Check for flange distortion. |
| |
| Thread
Fusing when Machine Stops |
| Cause |
Remedy |
| Poorly
finished or incorrect thread. |
Use better
quality thread, change to corespun thread. |
| Poorly
or harshly finished densely woven fabric. |
Improve
fabric finish. Change to more suitable needles. Apply needle
coolants. |
| Damaged
needle or needle overheated after thread break. |
Change
needle. |
| |
| Skipped
Stitches |
| Cause |
Remedy |
| Failure
of hook, looper or needle to enter thread loopsat correct time.
|
Check machine
clearances and timings. Check needle is inserted and aligned
correctly. Use needle with a deeper scarf. |
| Thread
loop failure due to incorrect needle size / style for thread
size / type. |
Change
needle size / style. |
| Thread
loop failure due to incorrect setting of thread control mechanism
causing thread loop starvation. |
Reset to
standard and check loop formation with a strobe. |
| Flagging
of fabric due to poor presser foot control or too large a throat
plate hole. |
Re-adjust
presser foot pressure (using Coats Tension Meter). Change the
throat plate to match the needle. |
| Needle
deflections or bent needle. |
Use a reinforced
needle, reset the needle guard. Replace the needle. |
| Incorrect
sewing tension in the needle or underthreads. |
Re-adjust
(using Coats Tension Meter). |
| Poor
thread loop formation. |
Check with
a strobe. Change to filament based corespun or locked filament
polyester thread. |
| |
| Unbalanced
- Variable Stitching |
| Cause |
Remedy |
| Incorrect
sewing tensions. |
Check for
snarling, increase thread tension (using Coats Tension Meter). |
| Incorrect
threading. |
Rethread
machine. |
| Needle
thread snagging on bobbin case or positioning finger. |
Polish
bobbin case surfaces. Reset positioning finger and opening finger
if fitted (check with a strobe). |
| Variable
tensions due to poor thread lubrication. |
Change
to better quality thread. |
| |
| Staggered
Stitching |
| Cause |
Remedy |
| Needle
vibrating or deflecting. |
Increase
needle size or change to a reinforced or tapered needle. |
| Incorrect
or blunt needle point. |
Change
the needle. |
| Incorrect
needle-to-thread size relationship. |
Incorrect
needle-to-thread size relationship. |
| Feed
dog sway. |
Tighten
feed dog. |
| Poor
fabric control, presser foot bounce. |
Reset presser
foot. (using Coats Tension Meter). Change feed mechanism. |
| |
| Variable
Stitch Density |
| Cause |
Remedy |
| Poor
fabric feed control. |
Increase
presser foot pressure. Change to more positive feed mechanism. |
| |
| Variable
Seam Pucker |
| Cause |
Remedy |
| Variable
differential fabric feed. |
Improve
fabric feed mechanism and set with Coats Tension Meter. |
| |
| Other |
| Cause |
Remedy |
| Various
|
Contact
Coats Technical Services |
