How to go to a negative Z

[Johncoffee]

In order to do some calibration stuff, I'd like to move the nozzle to a negative Z value. (e.g. when at 0 the head is for example still 1mm above the bed). It seems that I can't move the head lower - the command is simply not executed (G1 Z-0.1 or clicking Z- on the controls). The Z position value however decreases - but the head doesn't move.
I've selected "Allow negative Z" in the Printer settings in MAttercontrol to no avail.

Any help how I can do this?
Thanks - *John*

[Eaglezsoar]

Replying to refresh, can any forum user help Johncoffee with the problem he is having?

[Nylocke]

The Mattercontrol setting likely doesnt do anything. I'd recommend using the LCD interface (set z 0 in config menu)

[Johncoffee]

Thanks Eaglezsoar for bumping!:-)

It's not Mattercontrol that doesn't do anything as I can see the command G1 Z-0.1 being sent on Terminal. The Rostock Max V2 or most probably Repetier prevent me from doing this via a Terminal command. Of course the knob would be possible but via the buttons on Mattercontrol / Terminal command would be beneficial. Is there any way of bypassing the limits?

[Johncoffee]

It appears that a negative Z probing had been already discussed in 2014 in this forum : http://forum.seemecnc.com/viewtopic.php?f=57&t=4667
Even there are other suggestion to calibrate with the screws, I think that using the Rostock Max V2 internal Z measuring can be helpful to calibrate it -instead using a additional depth sensor for example. I negative Z-heights would be allow, the calibration can be done without changing the end screw positions at the towers.
By using commands like shown here would be interesting: https://www.youtube.com/watch?v=tDLbqLve128

[geneb]

The firmware won't permit negative Z moves.

g.

[Johncoffee]

...but interestingly it does when using the knob at the front panel...

[Nylocke]

Thats a special feature. Its an illegal move except in a firmware implemented exception.

[Johncoffee]

my firmware is original - no mods made.
Anyway - I think need to find a another way without negative Z playing around

[Nylocke]

No, as in Repetier has that feature implemented through the LCD. Its a stock feature. It can't be accessed outside of that menu.

[geneb]

It's designed specifically to allow you to set the Z-zero point from the LCD.

g.