Comparison Of Electrical And Hydraulic Drive Systems - Siemens SINUMERIK 840D Description Of Functions

1 General

1.2 Comparison of electrical and hydraulic drive systems

1.2 Comparison of electrical and hydraulic drive systems
Table 1-1 Comparison of electrical and hydraulic drive systems
Criterion Electrical direct drive
S
Power density /
Electrical part on
mounting
machine table
space require-
S
is light and requires
ments
little space.
Mass inertia of Electrical part on
moving parts machine table has low
mass.
Operational Service life depends in
reliability, ser- principle only on linear
vice life guides.
Servicing Simple replacement
Energy storage Peak requirement must
be installed as no storage
possible.
Maximum Peak thrust per unit area
forces approx. 40 to 80 kN/m
Load stiffness Very good;
Servo gain can be set to
betw. 10–100 times
higher than on the other
two drives.
Maximum Up to 500 m/min
velocity
Maximum Unlimited
travel path
Collision Mechanically difficult
protection
1-16
SINUMERIK 840D/SIMODRIVE 611 digital Descr. of Functions HLA Module (FBHLA) – 04.00 Edition
Electrical drive with
leadscrew
S
Servomotor and lead-
screw large and
heavy.
S
Problematic with lim-
ited mounting space.
Servomotor and lead-
screw have high mass
moment of inertia.
S
Shock-sensitive.
S
Service life limited by
leadscrew.
S
Sudden failure
possible.
Expensive replacement
and repair of leadscrew by
specialists.
Peak requirement must be
installed as no storage
possible.
Restriction with larger
2
forces.
S
Elasticity under large
forces.
S
Elasticity of leadscrew
is largely compen-
sated as a control
function.
@ ω
v =h /2π
max s max
h =thread lead
s
ω
=max. motor speed
max
v 6 m
Mechanically possible
Hydraulic drive
S
Cylinder and servo sole-
noid valve are light-weight
and compact.
S
Transfer of E motor to
hydraulic power unit.
Piston and piston rod have
very low mass
S
Protected against overload
by pressure limitation.
S
Sturdy, insensitive to
shocks.
S
Cylinder seals and valve
control edges have long
service life.
S
Warning of wear.
S
Simple error diagnosis
S
Simple replacement and
repair of valves and cylin-
ders.
S
Compensation of energy
requirement peaks by hy-
draulic accumulator.
S
Rapid traverse in differen-
tial circuit.
S
Reduction of installed ca-
pacity.
Practically unlimited (v6MN)
(Cylinder φ, p
=315 bar)
max
S
Oil compressibility is com-
pensated as a control
function (I component).
S
Good zero overlap quality
of valve ensures very high
rigidity under load.
120 m/min
with standard servo-cylinder
t 1 m
Mechanically possible
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02.99