Adjusting Z offset in Cura

[Link 34]

Hi,

 

I have spent time levelling the bed on my 2+ with PLA and now want to print with PETG, but PETG requires a greater Z offset (an extra 0.2mm), I don't want to re-level the bed and would rather add 0.2 to the z height in Cura, is there a way to do this ?, there used to be a setting which indicated it could do this but it is not any longer present in Cura 3.1. How can I do this ?

 

Thanks

[yellowshark 153]

 

OK the simple part to the answer is that yes you can, use the G92 command in your start gcode, e.g. my start code has

 

G92 Z209.055 ;set z-offset

 

The more difficult part is what do YOU set the Z position to?

 

In the above gcode statement we need to understand that

 

1.     The Z height for my printer is 216.00mm, measured from the printer bed surface to the nozzle. If I had used G92 Z216 then the printer bed would rise right up to the nozzle but let us say 1mm short of the nozzle if that is the gap that I introduced during the levelling process.

 

So why is it 209.055?

 

2.     Firstly because my printer bed has a glass plate on top of it and when I do the levelling I remove the glass plate and so I have to take that into account, otherwise the glass plate will be driven into the nozzle. Let us say the glass plate is 7mm high then I would use G92 Z209  (i.e 216-7).

 

3.     So where does the 0.055 come from? That is my fine tuning which puts the glass plate 0.055mm closer to the nozzle than set by the levelling process, to get the first layer really squashed down.

 

4.     So if like you I needed an extra 0.2mm I would set my Z statement to Z 208.855

 

5.     BUT you need to be careful, your printer and firmware may not work the same as my printer. There are two considerations.

 

6.     Firstly if you have a plate. How does your hardware/firmware handle that? Hopefully your printer instructions will give you details on this.

 

7.     Secondly which way around is your Z axis homing. Does Z0 move your bed to the bottom of the printer as mine does, or is it the other way around?

 

 

On my printer, which uses Repetier Host, I can send a line of gcode direct to the printer which makes this stuff very easy to test. If you do not have this capability then I guess you will just need to start a

print and then cancel it once the bed has been fully raised to start the printing.

 

What you do not want to do is ram your bed or plate into the nozzle so take it carefully.

 

[Link 34]

Thanks for the detailed info !. My Ultimaker 2+ uses the Ultigcode output from Cura so not sure it is as simple as editing the Gcode to change z height. 

 

I was was hoping that Cura would offer a feature for the 2+ to do this ?.

 

i think someone mentioned that the Tinker version of firmware allows some adjustment, although I haven’t seen this documented and not sure about installing a non factory firmware. 

 

Thanks