JUKI LK-1900B series - Page 29

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Adjustment procedures Results of Improper adjustment
If the main shaft eccentric cam
❽
isnotxed,thisadjustment
shouldbecarriedoutafterdeningitspositionandxingit.
1. Loosen the two setscrews
❼
of the crank balancer
❻
.
2. Using the two setscrews
❷
, remove the crank rod cover
❶
.
3.Turnthemainshaftinthedirectionofforwardrotation
A
so that
the needle bar
❸
lowers and the clearance between the needle
bar connecting
❹
and the needle bar bushing, lower
❺
is 5.7 mm
(LK-1903B,1903BN:4.6mm).
4. In the state that the two setscrews
❼
of the crank balancer
❻
as-
sumethehorizontalconditionandtheyaremovedinthedirection
of the arrow mark
B
, keep the close contact with the main shaft
eccentric cam
❽
and tighten the two setscrews
❼
. When tight-
ening these two setscrews
❼
, the screws should be tightened
reciprocally.
o
 Iftheangleforxingthecrank
balancer
❻
isinadequate,vibra-
tion of sewing machine operation
willbeintensied.
o
If the sewing machine is used for
alongtimewhilethexingposi-
tionisinadequate,theoperation-
al life of the main shaft bearing
maybeshortened.
o
If the crank balancer
❻
is not
moved in the direction of the
arrow mark
B
,theremaybe
interference with the sewing
machine frame.
Adjustment procedures Results of Improper adjustment
1. Lower shaft backlash
1) Loosen the two setscrews
❶
.
 2)Turnthelowershaftrearmetal
❷
in the direction of the arrow
andadjustthebacklash,keepingthemetaltocontactclosely
with Face A.
Size of backlash is 0.1 mm at the tip of the driver
❺
.Theshaft
isrequiredtorotatesmoothly.
 3)Tightenthetwosetscrews
❶
.
(Caution) When eliminate the backlash, the direction of rotation
should always be kept in the direction of the arrow.
2. Lower shaft connection/disconnection
1) Loosen the two setscrews
❼
.
 2)Thelowershaft
❻
can be taken out if it is pulled in the direc-
tion
C
of the arrow.
3) When mounting the lower shaft
❻
, insert it in the lower shaft
rear metal
❷
and the lower shaft gear
❸
.Applyoneofthe
setscrews
❼
totheatsection
❽
of the lower shaft
❻
and
tightenitapproximatelyinthecenter.Tightentheremaining
setscrew
❼
.
* Connection and disconnection of the lower shaft
❻
becomeeasy
if the above-mentioned backlash has been relieved in advance. In
thiscase,backlashadjustmentmustbedoneafterthelowershaft
❻
has been installed.
o
 Ifthebacklashisexcessive,the
hook noise will be increased.
o
If backlash is too small, the low-
er shaft gear
❸
or the oscillator
❹
will give rise to frictional wear.
In addition, this can be a cause
of crank rod lock-up.
o
If the front or rear position of
the lower shaft rear metal
❷
is
displaced at the time of backlash
adjustment,thiscanalsobea
cause of the lock-up of oscillator
❹
or the crank rod.