G90 Absolute mode

Mach3 Mach4 G-code · Mill

Axis values are positions from the active work zero.

Format

G90

Addresses

Address	What it does
`G90`	No address words

How it works

Modal, distance group.

Example program

G0 G20 G90 G54 G17 G40 G49 G80 (SAFE START, INCH)
G90 (ABSOLUTE)
G0 X1.0 Y-1.0 (HOLE 1)
X2.0 (HOLE 2)
…

The full 6-line example is in the app. Example is in inch. Check offsets and clearances first.

Watch out for

Mach4 G10 sets offsets in G90 and adds to them in G91.
Put G90 in every safe start line. G91 left on from MDI is a classic crash.

Related codes

G91 · G90.1

G90 on other controls

The same number can mean something different on another control.

Control	Meaning
Fanuc	Absolute programming
Haas NGC	Absolute positioning
Mazak (EIA)	Absolute programming
Okuma OSP	Absolute programming
Mitsubishi M70 M80	Absolute programming
Brother Speedio	Absolute programming
Siemens 840D 828D	Absolute dimensions
Heidenhain TNC (ISO)	Absolute dimensions
Fagor 8055 8065	Absolute programming
LinuxCNC Tormach	Absolute distance mode
Centroid CNC12 Acorn	Absolute positioning
Hurco WinMax (NC)	Absolute mode
Fadal	Absolute positioning
Swiss (Citizen Star)	OD turning cycle

Every G-code for Mach3 Mach4 in your pocket. The app has the full example programs, search by number or shop word, a line decoder and calculators for tapping, threading and drilling.

Open G90 in the app All Mach3 Mach4 G-codes

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