Functional Description - Siemens SINUMERIK 840C Installation Instructions Manual

09.95

12.6.2 Functional description

Whereas machine movements are executed in the real machine coordinate system,
programming is carried out in the ficticious (Cartesian) coordinate system. Fictitious axes must
be defined especially for the fictitious coordinate system. A fictitious axis can only be traversed
when transformation is selected. Fictitious axes can be selected freely with respect to their
axis name and their location. Up to eight transformations with varying axis groupings can be
defined in any one control. The definition consists of a transformation data set and the
associated parameters for each transformation.
The selection of the coordinate transformation is realized via G functions in the part program
or via the command channel from the PLC.
The following G functions are defined:
G131, G231, G331 coordinate transformation TRANSMIT
G133, G233, G333 2D coordinate transformation
G135, G235, G335 3D coordinate transformation
Coordinate transformation can be cancelled via G130, G230 or G330 in part program, or via
the command channel from the PLC.
It can be specified via NC MD 540* bit 7 whether cancellation occurs automatically on RESET
of after a change in the operating mode.
See Section "Coordinate transformation" for applications of the coordination transformation
TRANSMIT.
2D coordinate transformation - see Section "Coordinate transformation".
3D coordinate transformation - see Section "Coordinate transformation".
and in the Programming Guide to System 840C.
Note:
• When TRANSMIT is implemented, the programmed path velocity is reduced to a level
where the maximum speed of rotation of the rotary axis is not exceeded. This applies
especially to movements near the turning centre.
The speed is also reduced in rapid traverse if the rotary axis is not involved in the
movement.
• In the case of JOG mode, the feedrate reduction will only have a partial effect as the end
point of the movement is not known. This can lead to drops in the feedrate.
• The use of angle head cutters is restricted in TRANSMIT mode, block search with
calculation triggers an alarm.
Notes on TRANSMIT for SW 5 and higher
• Machining contours near the turning centre:
The new function calculates the permissible feedrate in the fictitious coordinate system as
a function of the current distance of the contour from the centre of turning and the MD
"Maximum velocity rotary axis" such that the path feed changes continuously.
In this way, the feedrate on the contour is always the maximum possible feedrate. At very
low feedrates, larger velocity fluctuations of the rotary axis can occur because of the
limited calculation precision.
© Siemens AG 1992 All Rights Reserved
SINUMERIK 840C (IA)
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12 Functional Descriptions
12.6.2 Functional description
12–19