11
Ball screw drives KGT
This large number of influencing parame-
ters shows clearly that it is not possible to
have a general regulation on lubricating
intervals for all operating conditions. It is
also not easy to specify a constant value
for the definition of lubricating intervals.
For antifriction bearings the value that is
preferably used is the number of revolu-
tions. Other standard values, e.g. operat-
ing hours or service life, can then be easily
derived from the number of revolutions.
Numerous tests have shown that lubrica-
tion should be performed after approxi-
mately
1.5 to 2.5 x 10
7
revolutions.
The smaller numerical value should be
used for ball screws with large diameters
and return ducts or multi-turn return
ducts. The theoretical interval is then cal-
culated from the average speed, length
and the lead.
The table below shows an example of
lubricating intervals in hours and kilome-
tres based on 2 x 10
7
revolutions.
Average speed [min
-1
]
Lubricating
interval [h]
500
667
1000
333
1500
222
2000
167
2500
133
3000
111
Lead [mm]
Lubricating
interval [km]
5
100
10
200
20
400
25
500
40
800
50
1000
5.4 Greasing and assembly
If the ball screw drive is not greased upon
delivery, the nut must be greased through
the lubricating hole before first use. When
the ball screw nuts are lubricated before
use and again later through the lubricating
hole, it should be remembered that the
lubricating grease is quite viscous and
does not spread evenly in the nut. This
makes it difficult to fill the nut with the
amounts stated in the table. For this rea-
son it is recommended to fill the nut in
several steps and to move the nut briefly
along the screw so that the grease can
spread evenly along the turns. It is usually
sufficient to turn the nut just a few rota-
tions (at least one nut length). Please
ensure that a collar of grease is produced
on both ends of the nut.
When a pre-greased ball screw nut is
mounted on the respective ball screw,
check whether a certain amount of lubri-
cating grease is lost at the end of the trav-
el (end of the screw). If the loss is exces-
sive, it is recommended to fill in some
more grease through the lubricating hole
of the mounted ball screw nut to ensure
that the amount of grease is sufficient
again.
5.5 Explanation
All values given are only approximate and
are based to a certain extent on values
gained through experience. It is therefore
essential to inspect the ball screw drive
regularly and that any signs of insufficient
lubrication, e.g. dry screw or high loss of
grease be amended.
Please see also the relevant notes in the
catalogue.
