RE: [CAD_CAM_EDM_DRO] DIFFERENCE BETWEEN G90 & G91?

Most CNC controllers can accept coordinate data in
Absolute or in Incremental mode.
G90 denotes a program to be in Absolute units
G91 denotes a program to be in Incremental units

G90

Absolute coordinates are where the positions of points
are measured from a common datum/zero point.
For example a tool is to moved from point A to
point B and then to Point C where the points have
the following coordinates :-

A X20,Y10

B X30,Y15

C X60,Y40

A G-code program in Absolute Mode would look like :-

N10 G90
N20 G01 X20.0 Y10.0 F300.0
N30 X30.0 Y15.0
N40 X60.0 Y40.0

G91

Incremental coordinates are where the positions of points
are measured from the previous position of the tool.
The above example in Incremental mode :-
(Assumes the tool is starting from X0,Y0 coordinates)
N10 G91
N20 G01 X20.0 Y10.0 F300.0
N30 X10.0 Y5.0
N40 X30.0 Y25.0

Regards

Michael


-----Original Message-----
From: woodknack [mailto:wjdupont@...]
Sent: 21 January 2002 16:07
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] DIFFERENCE BETWEEN G90 & G91?


What is the difference between G90 which is absolute mode and G91
which is incremental mode. Can someone break down what absolute mode
and incremental mode is. Its probably very simple, Im just very new
to this.


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