What is Absolute Dimensions (Absolute Programming)?
With Absolute dimensions or Absolute programming, the programmed position always refer to the zero point of the currently valid coordinate system (workpiece-zero-point).
G90 Absolute Dimensions or Absolute Programming is Modal G-code. Siemens Sinumerik provides AC (non-modal absolute dimensions) command to access individual axis absolute position.
CNC program example is here Sinumerik Mill Program – Absolute Dimensions Commands G90 AC
G90 – Modal Absolute Dimensions
If a CNC machinist want to program a part in absolute programming then simply the best way is to use G90 absolute dimensions command (normally called G90 absolute programming g-code ).
G90 is a modal G-code so will stay active until you program G91 Incremental Programming G-code.
G90 Modal Absolute Dimensions Format
AC – Non-modal Absolute Dimensions
But if you are programming a part in Incremental programming (G91) and just want to access one or some axis Absolute Coordinates then no need to use G90 command you can use Siemens Sinumerik AC (Non-modal Absolute Dimensions) command.
Siemens Sinumerik AC (Absolute Coordinates) command is the simple and short way to access non-modal absolute dimensions for individual axis.
Non-modal absolute dimensions (AC) are also possible for spindle positioning (SPOS, SPOSA) and interpolation parameters (I, J, K).
AC – Non-modal Absolute Dimensions Format
AC – Command for the activation of non-modal absolute dimensions
<axis> – Axis identifier of the axis to be traversed
<value> – Position setpoint of the axis to be traversed in absolute dimensions.