Brief Description Of Gi Functions; Definition Of Leading And Following Drives - Siemens SINUMERIK 840C Installation Instructions Manual

04.96
PLC user interface
• Data block DB29 for axes
• Data block DB31 for spindles
12.18.2
The gearbox interpolation (GI) function replaces mechanical gear couplings (gears and
differentials) on the basis of software functionality and single-axis drives.
The advantage of the GI function as compared to a mechanical gear train is the variable
transmission ratio and the free definition of drive (leading quantity) and output (following
quantity).
The GI function makes it possible to achieve a highly accurate, kinematic link between several
axes and spindles which must be moved in a defined position and/or speed ratio with respect
to one another.
A gearbox interpolation grouping consists of at least one leading drive and one following drive.
The advantage of gearbox interpolation is that the user need only program the operating
characteristics of the leading drives. The following drive then responds according to the set
link factor.
The following drive setpoints are calculated from the setpoints or actual values of the leading
drives depending on the type of link selected. The GI function allows the transmission ratio
(link factor) to be freely programmed.
The SINUMERIK 840C makes the gearbox interpolation function available in parallel to the
basic interpolations (linear, circular, spline interpolation).
The following are typical GI function applications:
• Gear tooth machining on hobbers, gear shapers or grinders
• Complete, rear-face or "polygonal turning" machining operations on lathes
• Gantry machines (axes)
• Flying tool changes with magazine in motion (on-the-fly synchronization)
The gearbox interpolation function can be activated in all operating modes.
The experience gained from the applications of the electronic gearbox (ELG) and synchronous
spindle functions of the SINUMERIK 880 system formed the basis for the significantly
extended functional scope of the GI function provided by the SINUMERIK 840C.
Note:
With following axes, the handwheel function must not be activated without following-axis
overlay.

12.18.2.1 Definition of leading and following drives

The kinematic linking of two or more motions is generally based on the synchro system
principle. The movement of a motor or drive is detected by means of a path measuring system
(so-called leading motion) and applied to another servo drive as a manipulated variable
(following motion).
The servo drive, which follows the motions of other drives (so-called leading drives), is referred
to below as the "following drive". In the case of several leading drives, the following drive
position is determined from the overlay of the leading drive motions.
The GI function distinguishes between
• a real leading drive and
• a simulated leading drive.
© Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
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Brief description of GI functions

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12 Functional Descriptions
12.18.1 Corresponding data
12–129