Actually this post should be the first post of the CNC zone. As a new blogger i forget to say about this post. Well i think every cnc users know about G90 and G91 but here we discuss in brief. This is important to discuss because of further discussion about macro conditions and many more.
G90 is Absolute Coordinate system
G91 is Incremental Coordinate system
In G90 programming, all the values counted from predefined zero (origin) position.
In G91 programming, current position is zero for next position.
Lets take an example,
Absolute Program
N1 G0 G91 G28 Z0
N2 G90 G54 X20 Y20 M3 S2000
N3 Z5
N4 G01 Z0 F100
N5 X50
N6 Y45
N7 X75
N8 Y30
N9 X100
N10 Y80
N11 X75
N12 Y100
N13 X35
N14 Y69
N15 X20
N16 Y20
N17 Z5
N18 G0 G91 G28 Z0
N19 M30
Simulation of Absolute program
Incremental Program
N1 G0 G91 G28 Z0
N2 G90 G54 X20 Y20 M3 S2000
N3 Z5
N4 G01 Z-5 F100
N5 G91 X30
N6 Y25
N7 X25
N8 Y-15
N9 X25
N10 Y50
N11 X-25
N12 Y20
N13 X-40
N14 Y-31
N15 X-15
N16 Y-49
N17 Z5
N18 G0 G91 G28 Z0
N19 M30
Simulation of Incremental program
