12.93 12 Functional Descriptions
12.18.3 Operating principle
12.18.3 Operating principle
Several gearbox interpolation groupings can be operated simultaneously in the SINUMERIK
840 C system.
In principle, every real axis or spindle in the system can be defined as a following drive.
Likewise, every real or simulated axis or spindle may act as a leading drive. It is also possible
to program a drive to operate as the leading drive in several different GI groupings at once.
A following drive can, however, also be the leading drive in another grouping in order to allow
the cascading of GI groupings.
A single gearbox interpolation grouping consists of one following drive and up to 5 leading
drives.
A GI grouping can be configured in the following ways:
• One following axis (real) and max. 5 leading drives (real or simulated, rotary/linear axes or
spindles)
• One following spindle (real) with exactly one leading spindle (real or simulated) and a
maximum of 4 leading axes (real or simulated, rotary/linear axes).
In this case, the following drive is controlled by the leading drives. The leading drives and the
following drive can be programmed in different channels of the same mode group.
The following drive setpoint is derived from the part setpoints or part actual values (depending
on link type) of the leading drives. The NC multiplies these leading drive values with the
appropriate transmission ratio (link factor) and applies them to the following drive as a total.
Apart from these leading drives, the compensatory controller and overlaid following drive
motions can also supply an additional setpoint for the following drive.
FDSet = LD1*KF1 + LD2*KF2 + LD3*KF3 + LD4*KF4 + LD5*KF5 + FDover
FDSet = Part setpoint following drive
LD1..5 = Part setpoint or part actual value leading drives 1 to 5
K
F
1..5 = Link factor or transmission ratio between leading drives 1 to 5 and
the following drive
FDover = Additional following drive overlay
By programming the NC in a special way, it is possible to define a new gearbox interpolation
grouping even when a part program is already running. Inputs can also be made manually via
the GI input display in set-up mode.
The requirements of the control response of the coupled drives are in general considerably
higher than for normal NC drives.
The following basic conditions must be fulfilled to obtain a high degree of accuracy:
• Short position controller sampling times (particularly with actual value link)
• Dynamically well co-ordinated drives
• Most precise actual value information possible from the path measuring systems of leading
and following drives
• The transmission ratio K
F
between the leading and following drives should be less than 1 if
possible to ensure that a large leading movement results in a small following movement.
© Siemens AG 1992 All Rights Reserved 6FC5197- AA50
12–131
SINUMERIK 840C (IA)