As a relative CNC beginner, I have the following question. I have created my first G-code in PixelCNC, 
but my machine starts above the material instead of in the material. 
I compared the G-code start with my current CAM (Easel) and see the following difference 
(it is not he same project). Easel starts at Z6.000 and goes to Z-0.600. PixelCNC starts at Z6.100 and 
goes to Z5.40. Please help.
PixelCNC:  
( Generated by: PixelCNC v1.84b ) 
( Post: GRBL Metric.txt v1.10 ) 
G21 G90 G91.1 
( Buitenkant 1.4 bit ) 
( Spindle: CW 10000 ) 
M3 S10000 
G0 Z6.10 X15.42 Y22.07 
G1 Z5.40 F50 X15.26 Y22.20 F250 
X15.13 Y22.37 Y22.61    
Easel:   
G21 M3 S10000 
G90 
G1 Z6.000 F228.6 
G0 X59.413 Y149.523 
G1 Z-0.600 F75.0 
G1 X59.504 Y149.653 F350.0 
G1 X59.475 Y149.802 F350.0 
G1 X59.347 Y149.891 F350.0

Additional: the simulation gives the right position

Hi NicoClock,

Can you provide more information about what operations you're using in PixelCNC?

 - Charlie

I've used a 'simple' 2D profile milling with the following parameters. Would you like other information?

Hi NicoClock,

Thanks for sharing the operation parameters.

The machine origin for your project is set to the bottom of the canvas, which means that Z0.0 is the bottom of the canvas volume and Z6.0 is the top surface of the canvas volume. Any cutpaths generated will be inside of the canvas volume, i.e. their Z coordinates will be from Z0.0 to Z6.0.

The G0 Z6.1 is a move to the rapiding height above the canvas, because you have Rapid Height set to 0.1mm in your operation parameters. Then the subsequent XY move is to the start of the first cutpath before it feeds down to 0.6mm below the top of the canvas, per your operation's Cut Depth, which is going to be Z5.4.

It looks like you just need to move your machine Z origin to the top of the canvas, which you can do under Canvas Properties by clicking the up-arrow next to the 'Z Origin' parameter, which should set it to 6.0mm. Then click Apply and you should be able to export your G-code so that cutpath coordinates have Z0.0 as the top-surface of your workpiece, and the first layer of cuts will be at Z-0.6.

 - Charlie

Hi Charlie,

Thank you for your very helpfull answer. I will try your method tomorrow and will let you know the result. 

Nico

Hi Charlie,

Sorry for my late reply but now I have used your instructions and it works!  Thank you for this solution and learning.

Nico