Cylinder - Siemens SINUMERIK 840D Description Of Functions

02.99
A.2

Cylinder

General
Through-rod or
differential
cylinder
 Siemens AG 2000. All rights reserved
SINUMERIK 840D/SIMODRIVE 611 digital Descr. of Functions HLA Module (FBHLA) – 04.00 Edition
The cylinder acts as the drive element in the electrohydraulic control loop.
It converts the flow to a linear movement. In this case, high velocities are re-
quired for rapid traverse movements as well as slow velocities for machining
operations
On a through-rod cylinder, a piston rod of the same diameter is mounted at both
ends as a power transmission element. Consequently, the piston areas at the A
and B ends are identical. Likewise, at a constant piston speed, the incoming
flow is equal to the displaced flow in the settled state. The piston rods on the
through-rod cylinder thus travel in and out symmetrically.
In contrast to the through-rod cylinder, a differential cylinder has either a power-
transmission piston rod at one end only or the piston rods at its two ends have
different diameters. In the latter case, the piston areas at the A and B ends are
different. Furthermore, at a constant piston speed, the displaced flow is not the
same as the incoming flow. The maximum piston travel-in and travel-out speeds
are not the same on a differential cylinder (see Section 4.7).
This asymmetry can, however, be compensated by means of the piston area
adaptation function (MD 5112: VALVE_FLOW_FACTOR_A_B).
Apart from the piston diameter, it is necessary to specify the rod diameters at
the A and B ends. On a differential cylinder, both rod diameters are different,
one of the rods might even have a zero diameter. The maximum piston stroke
and cylinder dead volume are also required.
Through-rod cylinder
Differential cylinder
Fig. A-20 Cylinder principle
D D
2 0
A B
D
0
A B
D D
2 0
A B
A Hydraulics
A.2 Cylinder
D
1
D =D
1 2
D
1
D
1
0D
D
1 2
A-249