CNC Information | Learn CNC | CNC Programming G-Code

Hi, Im new to gcode and I have been looking through some of the programs at work
and have found that they all start with the following line
G40 G49 G80
I know G40 means cancel cutter diameter compensation and G49 means cancel tool
length offset and G80 means cancel motion mode, but I dont understand why they are at the first line in the program.

The programs are all for drilling on a Fanuc.

Any info appreciated thanks...

i don't know
but as a quick shot in the dark could it be because the previous code had set those parameters ?
and could there be a return to default settings or a previous profile setting that has been over ridden
it may be the handshake is indicative of set parameters in the post processor

Thanks, but the thing is that no length or diameter offset gets set in the
program prior to the G40 G49 and G80 commands.

Here is an example program(n.n is some decimal value)...

:5655
G40 G49 G80;
G92 Xn.n Yn.n Zn.n;
G90 G00 Xn.n Yn.n;
M06 T1;
S1500 M03;
G00 G43 Zn.n H1 M08;
G98 G82 Xn.n Yn.n Zn.n R3.0 F100;
Xn.n Yn.n;

M09;
G80
G00 G49 G27 Zn.n M05;
M06 T3;
S1000 M03;
G00 G43 Zn.n H2 M08;
G98 G83 Xn.n Yn.n Zn.n R3.0 Q4.0 F88.0;
Xn.n Yn.n;

M09;
G80 M05;
G00 G27 G49 Zn.n;
G27 Xn.n Yn.n;
M30;

Thanx

Dude ahh

This is a programmers religion! ESPECIALLY ON fanuc
always start your program with:
G40 G49 G80 G90
G40=CUTTER COMPENSATION CANCEL
G49=TOOL LENGTH COMPENSATION CANCEL
G80=CANCEL OR END CANNED CYCLE
G90=ABSOLUTE MODE

G80 IS VERY IMPORTANT WHEN DRILLING USING G81, G83, G84 AND SUB PROGRAMS
OTHERWISE WHETHER STARTING THE PROGRAM OR EVEN REPEATING A BLOCK OR IN THE MIDDLE OF A PROGRAM IT CAN REPEAT THE LAST CANNED CYCLE USED IN THE PROGRAM
SCAREY BUT TRUE, SO LIKE ALL OLD WISE KUNGFU MASTERS SAY, SAFETY BEFORE ACTION.

ANOTHER IMPORTANT CODE TO USE WHEN TURNING, ALWAYS USE G50 AND MAXIMUM SPEED ON THAT SAME LINE, EG N10 G50 S2000.
THIS WILL INSURE THE SPINDLE DOESNT REV OVER 2000RPM NO MATTER WHAT SPEED U PUT IN AFTERWARDS WITH G96 OR G97

Thank you very much, now i understand...