Absolute/Incremental Dimensioning: G90, G91, Ac, Ic - Siemens SINUMERIK 808D ADVANCED Programming And Operating Manual

Overview of typical dimensions
The basis of most NC programs is a drawing with concrete dimensions.
When implementing in a NC program, it is helpful to take over exactly the dimensions of a workpiece drawing into the
machining program. These can be:
● Absolute dimension, G90 modally effective applies for all axes in the block, up to revocation by G91 in a following block.
● Absolute dimension, X=AC(value) only this value applies only for the stated axis and is not influenced by G90/G91. This
is possible for all axes and also for SPOS, SPOSA spindle positionings, and interpolation parameters I, J, K.
● Absolute dimension, X=DC(value) directly approaching the position by the shortest route, only this value applies only for
the stated rotary axis and is not influenced by G90/G91. This is also possible for SPOS, SPOSA spindle positionings.
● Absolute dimension, X=ACP(value) approaching the position in positive direction, only this value is set only for the rotary
axis, the range of which is set to 0... < 360 degrees in the machine data.
● Absolute dimension, X=ACN(value) approaching the position in negative direction, only this value is set only for the
rotary axis, the range of which is set to 0... < 360 degrees in the machine data.
● Incremental dimension, G91 modally effective applies for all axes in the block, until it is revoked by G90 in a following
block.
● Incremental dimension, X=IC(value) only this value applies exclusively for the stated axis and is not influenced by
G90/G91. This is possible for all axes and also for SPOS, SPOSA spindle positionings, and interpolation parameters I, J,
K.
● Inch dimension, G70 applies for all linear axes in the block, until revoked by G71 in a following block.
● Metric dimension, G71 applies for all linear axes in the block, until revoked by G70 in a following block.
● Inch dimension as G70, however, G700 applies also for feedrate and length-related setting data.
● Metric dimension as G71, however, G710 applies also for feedrate and length-related setting data.
● Diameter programming, DIAMON on
● Diameter programming, DIAMOF off
Diameter programming, DIAM90 for traversing blocks with G90. Radius programming for traversing blocks with G91.
8.2.2

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

Functionality
With the instructions G90/G91, the written positional data X, Z, ... are evaluated as a coordinate point (G90) or as an axis
position to traverse to (G91). G90/91 applies for 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 not 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 69)" and "Circular interpolation (Page 71)".
Programming
G90 ; Absolute dimension data
G91 ; Incremental dimension data
Z=AC(...) ; Absolute dimensioning for a certain axis (here: Z axis), non-modal
Z=IC(...) ; Incremental dimensioning for a certain axis (here: Z axis), non-modal
See the following different dimensioning types in the drawing:
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Programming and Operating Manual (Turning)
6FC5398-5DP10-0BA2, 06/2015