Pfaff 571 Instruction Manual page 121

Check list for correcting problems with the thread trimming device
Problem
The first stitches have not
been sewn
The needle thread has not
been cut
Cause
Bobbin thread clamp spring setting
is too strong
After trimming the needle thread is
too short
Bobbin thread has been cut too
short and is not picked up by the
centre hook of the catcher.
Balance wheel set too high, so that
the thread is not clamped between
needle hole and material after the
first stitch
Needle hole too large
Primary thread tension set too high
in front of the needle
Thread is not drawn into the catcher
Knife pressure is too low
Check list
Correction
See instruction manual (Chapter
Bobbin thread clamp spring)
primary Check/adjust the tension.
Check/adjust the position of the
control cam (see instruction manual
Chapter Radial position of the
control cam)
Check/adjust Parameter 707.
Check and adjust catcher path and
position (see Chapter Position of
the thread catcher Page 4)
Adjust the height of the balance
wheel (see instruction manual
Chapter Height of the balance
wheel)
Install new insert and extend it to
the dimension required
Insert new, weaker spring (see
Pages 2 – 3)
Check/adjust Parameter 707.
Check/adjust primary tension.
Check/adjust position of control cam
(see instruction manual Chapter Ra-
dial position of the control cam)
Adjust the pressure of the knife (see
instruction manual Chapter Knife
position and knife pressure)
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