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21.2 Errors in the sewing process
Error
Unthreading at seam
beginning
Thread breaking
Missing stitches
118
Possible causes
Needle thread tension is
too firm
Needle thread and hook
thread have not been
threaded correctly
Needle is bent or sharp-
edged
Needle is not inserted
correctly into the needle
bar
The thread used is
unsuitable
Thread tensions are too
tight for the thread used
Thread-guiding parts such
as the thread tube, thread
guide or thread take-up
disk are sharp-edged
Throat plate, hook or
spread have been
damaged by the needle
Needle thread and hook
thread have not been
threaded correctly
Needle is blunt or bent
Needle is not inserted
correctly into the needle
bar
The needle strength used
is unsuitable
The reel stand is installed
incorrectly
Thread tensions are too
tight
Throat plate, hook or
spread have been
damaged by the needle
Service Instructions 878-M PREMIUM - 03.0 - 10/2019
Troubleshooting
Remedial action
Check needle thread tension
Check the threading path
Replace the needle
Insert the needle correctly into the
needle bar
Use the recommended thread
Check the thread tensions
Check the threading path
Have parts reworked by qualified
specialists
Check the threading path
Replace the needle
Insert the needle correctly into the
needle bar
Use the recommended needle
strength
Check the assembly of the reel
stand
Check the thread tensions
Have parts reworked by qualified
specialists
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