Siemens SINUMERIK 840D Description Of Functions page 34

2 Configuring
2.3 Configuring the hydraulic drive
Characteristic
+Q
10
–U
E
–Q
Fig. 2-10 Characteristic of servo solenoid valve
Servo solenoid or
HRV valves
2-34
SINUMERIK 840D/SIMODRIVE 611 digital Descr. of Functions HLA Module (FBHLA) – 04.00 Edition
Values with either a linear or knee-shaped characteristic can be selected.
The latter are suitable for obtaining a higher resolution in the low signal range
(machining) and sufficient flow in the high signal range (rapid traverse).
The definition of the knee-point position as 40% or 60% means that only 10 %
of the opening cross-section (flow) is released at 40% or 60% of the control sig-
nal (i.e. at U=4 V or 6 V).
The knee-shaped characteristic of the valve must be linearized in the HLA mod-
ule to adapt it to the closed-loop control of the entire drive (cylinder).
Rapid traverse
+U –U
E E
40
Machining
velocity
Note
Recommended selection:
Servo solenoid valves are generally recommended for applications where there
is a clear separation between machining operation and rapid traverse.
HRV valves (High Response Valve) are characterized by a better dynamic re-
sponse, i.e. by a higher limit frequency as compared to servo solenoid valves.
They react with greater sensitivity to setpoint changes especially in the small-
signal range. The use of HRVs is recommended in the following cases:
1. When extremely high contour precision is required in high-speed continu-
ous-path control machining operations.
2. When very high response sensitivity is required to achieve the best possible
positioning accuracy.
It must be noted that HRVs do not generally have a "fail-safe" position. The con-
nector has 12 pins instead of the 7-pin connector on servo solenoid valves.
+Q
Valve
characteristic
Linearized
characteristic
10
+U
40
Compensation
–Q
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02.99
E