Comparison Of Electric And Hydraulic Drive Systems - Siemens Sinumerik 840D Series Function Manual

1 General

1.2 Comparison of electric and hydraulic drive systems

1.2 Comparison of electric and hydraulic drive systems
Table 1-1 Comparison of electric and hydraulic drive systems
Criterion Electric direct drive
S
Power density /
Low weight and
mounting
S
reduced spatial re-
space require-
quirements of the
ments
electric part on the
machine table.
Mass inertia of Electric part on machine
moving parts table has low mass.
Operational Service life depends in
reliability, principle only on linear
service life guides.
Servicing Simple replacement
Energy storage Peak requirement must
be installed as no storage
is 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 ve- Up to 500 m/min
locity
Maximum Unlimited
travel path
Collision Mechanically difficult
protection
1-16
Electric drive with
leadscrew
S
Servomotor and leads-
crew large and heavy.
S
Problematic with lim-
ited mounting space.
Servomotor and leads-
crew have high mass mo-
ment 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 is
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
max s max
h =thread lead
s
ω
=max. motor speed
max
v 6 m
Mechanically possible
SINUMERIK 840D/SIMODRIVE 611 digital, HLA Module (FBHLA) - 10.03 Edition
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
(cylinderφ, p
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.
/2π 30...300 m/min
(depending on which cylinder
seal kit is used)
v 3 m
Mechanically possible
 Siemens AG, 2003. All rights reserved
10.03
=700 bar)