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THE G54 REPORT
Your Reference Point for Fanuc Mastery
Job No.
J.O.B. 1 · OP30
This J.O.B.
●  OP10 — Welcome ●  OP20 — Alarms & Setup ●  OP30 — Q&A, Code & Bonus
06
Reader Q&A
"What's the Difference Between G90 and G91?"

Submitted by a reader new to Fanuc controls:

"What's the difference between G90 and G91 on a Fanuc control? I keep getting confused about when to use absolute versus incremental."
The Answer

On a Fanuc control, G90 represents absolute programming and G91 is incremental programming. When using G90, you are telling the machine that every coordinate given after this code is in reference to a certain position — i.e., work offset zeros for X, Y, Z, etc.

When using G91, every coordinate given is not referencing a fixed zero point, for example G54. Instead, it's telling the machine to move a certain distance from wherever it currently is.

So the same X1.0 command means something completely different depending on which mode you're in. In G90, it sends the machine to position X one inch from the X zero. But in G91, it moves the position in X one inch from its current position, no matter where it happens to be.
07
Code Snippet Vault
Copy It. Paste It. Run It.
Copy · Paste · Run
(TOOL LIST - EDIT HERE ONLY)
#1 = 1        (T1 - 1/2" FLAT ENDMILL)
#2 = 2        (T2 - CENTER DRILL)
#3 = 3        (T3 - 3/8" DRILL)

(TOOL 1 CALL)
T#1 M06
G43 H#1 Z.1
G01 G41 D#1 X_ Y_ F_

What it does: One variable drives your T, H, and D numbers — edit the tool list once at the top, and it updates everywhere.
★
Bonus: Off the Rack
Why Every Fanuc Robot on Earth Is the Same Color

Here's a true story for you: When Tesla was ramping up production, Elon Musk himself reportedly asked Fanuc to paint their robots black to match Tesla's branding.

Fanuc's answer? A polite no. Their robots had always been yellow, and they intended to keep it that way.

The color choice actually goes back to Fanuc's founder, Seiuemon Inaba, who had a personal passion for the color yellow because, in his words, it's "the emperor's color" in the Orient.

Decades later, that same color choice has become one of the most recognizable symbols in manufacturing — you can spot a Fanuc robot on a factory floor from across the room before you ever see the nameplate.

That's it for this issue. Go put this stuff to work — and if it saves you time on your very next setup, you'll know exactly why I write this thing.

Talk soon,

The G54 Report
P.S. — Got a question that's been bugging you on the machine? A macro you can't quite crack? Send it in. There's a real shot it ends up answered right here in a future issue.
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