09.01 12 Functional Descriptions
12.18.8 Following drive overlays
12.18.8 Following drive overlays
When the LINK ON gear link is activated, the following drive follows the movements of the
leading drives according to the link factors entered. At the same time, i.e. when LINK ON is
active, the following drive can be traversed with an additional overlay.
However, the following basically applies: The overlay is included in the calculation only if the
required enabling command from the PLC is present (interface signal ENABLE FD-OVERLAY).
1. Programmable positional offset of the following drive in the AUTOMATIC and MDA
modes
• Incremental positional offset of the following axis in the part program, e.g. G91 C... F...LF.
When an absolute overlay is programmed with G90, the following axis traverses into the
wrong position. Monitoring is not possible.
• Overlay of following axis to obtain an absolute offset to one or several leading axes (on-
the-fly synchronization)
• Overlay of following spindle to obtain positional synchronism with drives in operation (on-
the-fly synchronization)
2. Manual offset of following axis
• In the AUT or MDA mode: Overlay of following axis with handwheel with a
DRF offset.
• In the JOG and JOG-INC modes: Overlay of following axis with handwheel or with
directional keys.
• In the TEACH IN mode: Depending on mode, overlay of following axis
via directional keys or handwheel.
The overlay is traversed at the velocity programmed in each case.
ELG: With a following axis override, only 75% of the acceleration value are used for the
following axis. The remaining 25% are reserved for possible actual value linkage.
3. On-the-fly synchronization
For some applications (e.g. hobbing, synchronous spindles), the leading and following drives
must not only operate in synchronism, but also at a specific angle in relation to one another.
The term "On-the-fly synchronization" is used to describe the process of switching the link on
and over when the leading and following drives are already running, followed by automatic
positional synchronization of the drives. If NC MD 1848*/526* bit 2 is set, then a block change
is executed only when the drives are synchronized (interface signal SYNCHRONISM FINE).
"On-the-fly synchronization" can be selected via the part program (G403), the interface signal
ON-THE-FLY SYNCHRONIZATION ON or the input display. The function is operative in all
operating modes.
The link is switched on for the drives involved through specification of the synchronous
positions which can be entered in the part program or input display. Synchronization is
implemented as if all drives had started to traverse from the programmed synchronous
positions with the link activated. In other words, at the end of the synchronization process, the
drives are not at the programmed synchronous positions, but merely positionally offset in
relation to one another as determined by the synchronous positions.
A following drive and up to 5 leading drives can be synchronized simultaneously.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50
12–139
SINUMERIK 840C (IA)