STAR – Precision Ball Screw Assemblies

STAR – Precision Ball Screw Assemblies
General
DIN 69 051 Part 1 defines a
ball screw as follows:
An assembly comprising a ball screw shaft
and a ball nut and which is capable of
converting rotary motion into linear motion
and vice versa.
The rolling elements of the assembly are
balls.
Advantages over the Acme
screw drive
– The mechanical efficiency of an Acme
screw drive is a maximum 50%,
whereas a ball screw can reach a
mechanical efficiency of up to 98%
– Higher life expectancy due to negligible
wear during operation
– Less drive power required
– No stick-slip effect
– More precise positioning
– Higher travel speed
– Less heat-up
Due to their high mechanical efficiency,
ball screws are in principle not self-locking.
Safety information
We recommend that a safety nut be
installed for particularly critical applications
in vertical set-ups. Please ask.
Efficiency (%)
100
90
80
70
60
50
40
30
20
10
0
0
m = 0.005
m = 0.01
1 2 3 4 5 6 7 8 9
Selection criteria for ball
screws
The following factors should be considered
when selecting the ball screw for a given
application:
– degree of accuracy required (lead
deviation)
– in-service load conditions
– service life
– critical speed
– buckling load
– rigidity / permissible clearance or
desired preload
– charateristic speed
The following points should be taken into
consideration when selecting a ball screw
assembly that is to be both cost-efficient
and optimally designed:
– The lead is a decisive factor for the
load-carrying capacity (depending on
the maximum possible ball diameter)
and the drive moment.
– The calculation of the service life should
be based on average loads and average
speeds, not on maximum values.
– In order for us to provide you with a
customized solution, installation
drawings or sketches of the nut
environment should be enclosed with
your inquiry.
m = 0.2
m = 0.3
Ball screw
Acme screw
Lead angle (°)
N.B.:
Radial and eccentric forces relative to the
screw must be avoided as they have a
negative effect on the life and proper
function of the ball screw.
Where special conditions of operation are
involved, please ask.
78 RE 83 301/12.99