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1. ## Arc confusion

Hi!

I am having trouble with G02/G03 with IJK method.

This is the arc i am trying to define:

This is my attempt at the gcode

Code:
```M3 S4000 ;
G90 G21 ;
G0 Z0.500 ;
G0 X5.900 Y0.000 ;
G1 Z-0.700 F50 ;
G18 G03 X4.100 Y0.000 Z-0.700 I-0.900 J+1.2 F50 ;
G0 Z0.500 M2 ;```
It results in a tangetal arc like this:

My mill does not accept M90.1 so I have to work with I and K as relative coordinates.
I don't think i can use the R method since i sometimes need to move in Y as well.

How can i alter my program to move in the arc shown in my first image?

2. ## Re: Arc confusion

Not sure exactly what you are doing, but something like this.

M3 S4000
G90 G21
G0 Z0.500
G0 X5.900 Z-1.000
G1 Y-0.70 F50
G18 G03 X4.100 Z-1.0 I-0.900 K1.2 F50
G0 Z0.500 M2

3. ## Re: Arc confusion

Mills use G17 for standard arcs where the centre point is on the same plane as each point on the arc...
so G17 XY & IJ
G18 XZ & IK
the 3rd axis is sometimes used for creating a helical move

so to correct your program... get rid of G18... or change to G17
G2 is for clockwise movement.... G3 for CCW

plus the M2 should be on the last line, by itself

Try this for G17 .. using IJ
Code:
```G21 ;    ( inch programming... by itself )
G17 G90 ; ( safety lines.... XY plane, absolute )
M3 S4000 ;
G0 Z0.5 ;
G0 X5.9 Y-0.7 ;
G1 Z-0.7 F50 ;
G02 X4.1 Y-0.7 I-0.9 J1.2 F50 ;
G0 Z0.5 ;
M2 ;```
Try this for G17 .. using R
Code:
```G21 ;    ( inch programming... by itself )
G17 G90 ; ( safety lines.... XY plane, absolute )
M3 S4000 ;
G0 Z0.5 ;
G0 X5.9 Y-0.7 ;
G1 Z-0.7 F50 ;
G02 X4.1 Y-0.7 R1.5 F50 ;
G0 Z0.5 ;
M2 ;```
I also stripped trailing zeros, as they are not necessary

4. Removing feedrate from the G03 instruction seem to work in the simulator at least. I am writing a python program that generates this code thus the trailing zeroes. I will use it to engrave text in a groove. That is why i use G18 (XZ plane) and the additional Y coordinate.

This code works in the simulator:

Code:
```G21 ;
M3 S4000 ;
G90 ;
G0 Z0.500 ;
G0 X5.900 Y0.000 ;
G1 Z-0.200 F50 ;
G18 G03 X4.100 Y0.000 Z-0.200 I-0.900 K1.200 ;
G0 Z0.500 ;
M2```
Does it look OK?

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