<p>I am working on g code for my homebrew 3d printer and i have found the line <code>G1 -2.000 F2400.000</code>. From what i understand there should be an axis before the number and x and y shouldnt have negative. I am using grbl which is for cnc milling but and i have been deleting this line with no problems but i am wondering what it does because i will be upgrading to a "real" 3d printer asap</p>

G1 indicates a movement and -2.000 the distance, F2400.000 the feed rate mm/min, normally the
(-)
values are for retraction on extrusion
E
, for example:
G0 X12 (move to 12mm on the X axis)
G0 F1500 (Set the feedrate to 1500mm/minute)
G1 X90.6 Y13.8 E22.4 (Move to 90.6mm on the X axis and 13.8mm on the Y axis while extruding 22.4mm of material)
```
```
1. G1 F1500
2. G1 X50 Y25.3 E22.4
```
```
In the above example, we set the feedrate to 1500mm/minute on line 1, then move to 50mm on the X axis and 25.3mm on the Y axis while extruding 22.4mm of filament between the two points.
```
```
1. G1 F1500
2. G1 X50 Y25.3 E22.4 F3000
```
```
However, in the above example, we set a
feedrate of 1500 mm/minute
on
line 1
, then do the move described above
accelerating to a feedrate of 3000 mm/minute
as it does so. The extrusion will accelerate along with the X and Y movement, so everything stays synchronized.
So, in your case if some axis is not defined the feed rate applies to all motors.
(part of this content is from reprap-wiki)
You will see negative numbers if your starting point is on the center of the bed just like rectangular coordinates.
```
```
G1 X-50.318 Y8.849 E11.70313 
G1 X-52.606 Y3.087 E12.26689 
G1 X-53.240 Y1.297 E12.43953 
G1 X-54.398 Y-2.097 E12.76562 
G1 X-54.683 Y-2.995 E12.85132
```
```