JUKI LH-4128-7 Engineer's Manual page 49

Adjustment Procedure
4) Position of the thread trimming cam and the thread trimming timing
1. Let the arm's engraved marker dot
dot (red) of the hand wheel
2. In the state that the knife driving arm
stopper of the thread trimmer driving arm, push in the cam roller
and set it in the groove of the thread trimming cam
3. In this state, turn the thread trimming cam
position. In this position (midpoint where the groove shape of the thread
trimming cam changes from straight to diagonal), tighten the tight-
ening screws (2 pcs.) of the thread trimming cam
o Checking the thread trimming timing
1. Push in the cam roller
the cam groove.
2. Turn the hand wheel
chine revolving direction and stop it where it is hooked. Confirm in this
case that the engraved marker dot (red) of the hand wheel
coincides with the arm's engraved marker dot
o Thread trimmer cam position check
1. In the state that the thread trimmer drive arm stopper
with the knife drive stopper
groove-state straight section of the thread trimmer cam
the position of the cam roller
2. Confirm that the cam roller
match in that position and it can be pushed in the groove of the thread
trimmer cam .
5) Clearance between the thread trimming cam and the thread loos-
ening arm
1. Push in the thread relieving arm
2. At that time, adjust the position of the stopper
of 0.5mm is secured between Face B on the right end face of the
thread trimming cam
ing arm .
coincide with the engraved marker
.
is keeping contact with the
as far as the illustrated
until it assumes the posture being settled in
in the direction opposite to the sewing ma-
, turn the hand wheel
.
does not involve any mechanical mis-
.
and the roller section
.
.
exactly
.
keeps contact
so that the
comes to
so that Clearance A
of the thread reliev-
– 45 –
Results of Improper Adjustment
Thread trimming
Thread trimming
timing is exces-
timing is exces-
sively advanced.
sively retarded.
If the thread trimming timing is
excessively advanced:
o Needle thread will come of the
needle eyelet.
o Thread trimmer will fail to
operate normally, which will
result in thread trimming failure.
o Needle thread clamp failure will
occur at the time of thread
trimming.
If the thread trimming timing is
excessively retarded:
o The needle will interfere with the
wiper.
o Thread trimming failure will
occur.
When the clearance is large:
o The amount of disc floating in the
disc floating mechanism be-
comes insufficient and a thread
trimming error is caused.
When the clearance is small:
o The roller section
contact with the thread trimming
cam and the thread trimmer
cannot function.
comes in