4.
Remove the T
inspection
plate at
the rear
of
the top
of the
knee.
5.
Remove the access hole
cover on the left hand side
of the knee.
6.
Slacken the
belt tension screw
on the motor bracket above
the motor
flange.
7. Support the
motor and
remove
the
four
screws
securing
the motor
and remove
the motor
The
dowel
pin,
underneath the
tension
screw, will
be released
so:nake sure
this item
is
located.
8.
Remove
the
two
fixing
screws
from
the top corners
of
the knee
front bracket and
replace
with
two screws
5/16 UNC
x
5"
long. These new screws
will allow
the
front bracket,
complete
with
the
Y axis ballscrew
to be slid
forward
to
give
clearance to
remove the
drive
belt.
9.
From
the
access
hole
in the knee remove
the
tormed copper
lubrication
pipe from the top
of
the ballnut.
Remove the
four
screws securing
-"he
ballnut
from its nut bracket.
10.
Measure and
record the distance
from
the ballscrew
pulley
to the bearing housing.
On
re-assembly this
figure
will
be
used
to
fix
the
pulley
in its original
position.
Release the taper
lock
holding
the
pulley.
11.
Withdraw the
front bracket
dowels and remaining
fixing
screws
and carefully
pull
forward the
front
bracket
complete with
the ballscrew assembly. The
second
person
should
guide
the
rear
of the leadscrew to maintain its
position
and avoid damage.
12.
The drive belt
and
pulley
is now slid off the rear of
the
leadscrew. Support
the
front bracket
and remove the rwo
support screws. The ballscrew assembly can
be withdrawn
from
thc'.
frcnt
of
the knee.
Disassemble
the ballscrew from
the
front
bracket.
1
3.
To replace a new ballscrew reverse the disassembly procedurc,
paying particular attention
to
the
following:
a. The ballscrew
assembly is supplied
from
the original manufacturer
protected in lanolin,
and
this must
be completely
removed.
Wash the assembly
by completely
immersing in CLEAN
white spirit
(NOT
PARAFFIN)
and brushing
well.
Run the ballnut
up the
full length
of the
screw to
ensure
complete
removal.
Allow the screw to drain
for an hour
and
blow
dry
using
a
mineral
based lubricating
oil
(Mobil
DTE 2+ or similar)
ensuring all moving
parts are
lubricated.
Fit
a
plastic
batl
(BM
part
number
8303822)
to plug the radial
lubrication
hole
not used
-
refer to the old screw
for
its corect
position.
b.
When
refitting the axis thrust bearings
ensure
that the
bearings are
back-to-back,
on
Fafnir
bearings, this is with the stamped
faces
of the
outer
rings
together.
To ensure
best results
the
high
points
of
eccentricity
should be together so
ensure
the
round burnish
mark
on each
bearing is
axially
in line. If there
is
any
doubt about the
condition
of these bearings,
they
should
be replaced.
The
fixing
screws
on
the
bearing
cap should
be tightened
to a torque
of
34
Nm
(25
lbft).
c. As
long as the rear bearing
remains
untouched
in the knee,
the alignment
of the
ballscrew
should
be maintained.
If
the alignment
is lost then
it is necessary to
remove the saddle,
as
described in Section
7
.3.2
and the alignment reset. The alignment
of the
ballscrew with
the
bedface and master
guideway
is critical
and must be
within
0.030
(0.0012")
along the
full
length of
the
ballscrew. Recheck
the alignment
when
the
fixing screws
have been tightened.
7-tt
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