Haas Mill · G-code
G90 Absolute Positioning
Positions are measured from part zero. The default and the safe choice for almost everything.
What G90 does on a Haas mill
In G90 every X, Y and Z is a location relative to the active work offset. Z-0.25 always means 0.25 below part zero, no matter where the tool is.
G91 is incremental: each value is a distance from the current position. It is useful for subprograms that repeat a pattern and for G28 retracts, but it is easy to forget it is active.
G90 format
| Address | Meaning |
|---|---|
G90 | Absolute |
G91 | Incremental |
G90 example program
G90 G00 X1. Y1. (go to X1 Y1)
G91 G00 X1. (move 1 inch further in X)
G90⚠ Watch out
Leaving G91 active after a G28 or subprogram turns the next "Z-0.5" into "go down another half inch". Always switch back to G90 on the next line.
Related codes
G90 questions
Should I program in G90 or G91?
G90 for almost everything. Use G91 only where it clearly helps and switch back immediately.
Independent reference. Not affiliated with, sponsored by or endorsed by Haas Automation, Inc. Haas is a trademark of its respective owner. Always confirm codes against your machine's operator manual — options and settings vary by model and software version.