Absolute/Incremental Dimensioning: G90, G91, Ac, Ic - Siemens SINUMERIK 808D User Manual

11.2.3

Absolute/incremental dimensioning: G90, G91, AC, IC

Fu n ctionality
With the instructions G90/G91, the written positional data X, Y, Z... are evaluated as a coordinate point (G90) or as an axis
position to traverse to (G91). G90/G91 applies to all axes.
Irrespective of G90/G91, certain positional data can be specified for certain blocks in absolute/incremental dimensions using
AC/IC.
These instructions do n o t determine the path by which the end points are reached; this is provided by a G group (G0, G1,
G2 and G3.... For more information, see Sections "Linear interpolation (Page 91)" and "Circular interpolation (Page 93)".).
Programming
G90
G91
X=AC(...)
X=IC(...)
See the following illustration for different dimensioning types in the drawing:
Ab solute dimensioning G90
With absolute dimensioning, the dimensioning data refers to the ze ro of the coordinate system currently active (workpiece or
current workpiece coordinate system or machine coordinate system). This is dependent on which offsets are currently
active: programmable, settable, or no offsets.
Upon program start, G90 is active for a l l axes and remains active until it is deselected in a subsequent block by G91
(incremental dimensioning data) (modally active).
In cremental dimensioning G91
With incremental dimensioning, the numerical value of the path information corresponds to the a xi s path to be traversed.
The leading sign indicates the tra versing direction.
G91 applies to all axes and can be deselected in a subsequent block via G90 (absolute dimensioning).
Sp ecification with =AC(...), =IC(...)
After the end point coordinate, write an equality sign. The value must be specified in round brackets.
Absolute dimensions are also possible for circle center points using =AC(...). Otherwise, the reference point for the circle
center is the circle starting point.
Programming example
N10 G90 X20 Z90
N20 X75 Z=IC(-32)
N180 G91 X40 Z20
N190 X-12 Z=AC(17)
Programming and Operating Manual (Milling)
6FC5398-4DP10-0BA6, 09/2017
; Absolute dimension data
; Incremental dimension data
; Absolute dimensioning for a certain axis (here: X axis), non-modal
; Incremental dimensioning for a certain axis (here: X axis), non-modal
; Absolute dimensions
; X-dimensions remain absolute, incremental Z dimension
; Switch-over to incremental dimensioning
; X-remains incremental dimensioning, Z-absolute
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