"Z-Height engrave must be negative" causing problem when z-axis directed down

[kirevdokimov]

I have a plotter where z-axis directed down, so

• Pen down is like Z 25,
• Pen up is like Z -25,

but I cannot set the values to the setup because pen down should be negative and pen up should be positive.

How to handle this situation?

[kirevdokimov]

Oh, I see I can simply use Individual commands to set up what does pen up and pen down means

[svenhb]

What's about inverting the motion direction via $3? To have the "normal" CNC behavior? https://github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration#---view-grbl-settings

[kirevdokimov]

Oh wow, $3=4 (dir port invert mask:00000100) worked for me, thank you @svenhb :)