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### Author Topic: CNC machines - Absolute and Incremental positioning - G90 G91  (Read 12810 times)

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#### stamatis

• Guest
##### CNC machines - Absolute and Incremental positioning - G90 G91
« on: August 23, 2008, 01:29:50 AM »
A machine can measure either from the zero point, or from the last position that was. For example, when you say "X10", you mean 10mm from the zero point of the axis X, or you may mean 10mm further than the last position the machine was on the X axis. The way of measuring is decided from the G codes G90 and G91. Running the G90 command, the machine will start to measure using absolute coordinates (measuring from the zero point of the axis) and running the G91 command will set the machine into "incremental measuring".

For making matters more clear, see the following two examples. They generate both exactly the same thing, a rectangle as shown in file p7.jpg. The first code example uses absolute measurements and the second uses incremental measurements. At this point it should be said that almost all machines measures by default using G90 (absolute coordinates). For the following example, we suppose that somehow, the machines start from point 10,10 and not 0,0

REM    --- a rectangle drawn using absolute coordinates ---
G90   ;Set absolute measurement
G1 Y80
G1 X80
G1 Y10
G1 X10

REM    --- a rectangle drawn using incremental coordinates ---
G91   ;Set incremental measurement
G1 Y70
G1 X70
G1 Y-70
G1 X-70
« Last Edit: August 23, 2008, 01:33:41 AM by stamatis »

#### spic0m

• Global Moderator
• Hero Member
• Posts: 841
##### CNC machines - Absolute and Incremental positioning - G90 G91
« Reply #1 on: August 23, 2008, 14:20:04 PM »
Nice! Keep'em coming

Quote
Line 1: N1 G0 X10 Y20 Z30
G0 means Rapid positioning of machine. So, in line 1, the machine will go to X10mm, Y20mm and the pen will have 20mm distance from the paper.

It's 30mm distance fr4om the paper.
« Last Edit: August 23, 2008, 14:22:30 PM by spic0m »

#### stamatis

• Guest
##### CNC machines - Absolute and Incremental positioning - G90 G91
« Reply #2 on: August 23, 2008, 17:43:32 PM »
Nice! Keep'em coming

Quote
Line 1: N1 G0 X10 Y20 Z30
G0 means Rapid positioning of machine. So, in line 1, the machine will go to X10mm, Y20mm and the pen will have 20mm distance from the paper.

It's 30mm distance fr4om the paper.

Of course!!! youre right. Thanx

Also, this means that at least one man hera has read my article. This makes me happy!!!!