Change z offset on Ender 3 V2

[Tooth 0]

Hi all,
i use an Ender 3 V2 and the Z offset that i store directly on the printer gets reset to 0 every time i restart the printer. It worked in the past but not anymore since a couple of weeks (i did not update anythin in between). Trying to save the offset on the printer does not change anything.
I have tried to fix the problem with the "Z Offset Setting" plugin, but as so many others, i can not enter negativ numbers (i need about -3mm offset).
I use a bl touch on my pinter that i also can not put ~3mm higher.

Is there another option to change the offset?

[Slashee_the_Cow 295]

It will let you put in negative numbers, just nothing beyond -0.44, It's designed to help adhesion, not to replace your printer's built in Z offset. It could be done with a post processor (I could probably do a brute force one for you that just reduces every Z value in a print or travel move), unless @ahoeben wants to show up in the meantime to point out some magic about their plugin I don't know.

[Tooth 0]

Can't i change somethin in the Start G-code. Setting this z value that stored on my printer somehow via code?
Cura also has this Post Processing Scripts, can't i add there some offset for any z position?

Thats how my start code looks like.

 

; Ender 3 Custom Start G-code
G92 E0 ; Reset Extruder
G28 ; Home all axes
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position
G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line
G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little
G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line
G92 E0 ; Reset Extruder
G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed
G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish

 

[Slashee_the_Cow 295]

27 minutes ago, Tooth said:

Can't i change somethin in the Start G-code. Setting this z value that stored on my printer somehow via code?
Cura also has this Post Processing Scripts, can't i add there some offset for any z position?

The complex answer is what always occurs to me first. I'm not sure if the gcode generated by Cura will ever change this during the print (I think it only resets the extruder). Try this after the G28:

G91 ; Relative positioning
G0 Z-2.8 ; Move Z axis 2.8mm down *example, change to your offset*
G92 Z0 ; Tell printer the current Z position is 0
G90 ; Return to absolute positioning, which I'm not sure if it'll reset this whole thing anyway

 

As for post processing scripts: definitely possible (I'm trying to do one myself now, but Cura is %$&*ing annoying when it comes to debugging - because there isn't any) but if I knew of any that did it already, I wouldn't be trying to deal with Cura writing my own.

Edited November 11, 2023 by Slashee_the_Cow

[Slashee_the_Cow 295]

Just for the sake of proving I'm crazy, I'm pretty sure my Z Offset post script is in a "done enough it works" state. I'm sure there's at least a 12% chance there's someone else out there who might find it useful, whether or not it's because of a problem with their printer or they're trying to print on top of something else or whatever.

 

In Cura, go to Help > Show Configuration Folder, then go into the scripts subfolder and drop the ZOffet.py file from the zip into there to make friends with all the other posts.

 

Restart Cura, go to Extensions > Post Processing > Modify G-Code. Click the Add a script button, scroll down to Z Offset and click on it. Then just enter the number you want (in your case -3, or you can be more precise), click Close and hope I'm at least half as good as I make myself out to be. You can load the gcode in Cura before you print to have a look, but I'm not sure it can display it properly:

It's not supposed to have that extra bit at floor level. Try a small test print first. Let me know how it goes.

ZOffset.zip

[ahoeben 1,953]

13 hours ago, Slashee_the_Cow said:

It's designed to help adhesion, not to replace your printer's built in Z offset.

This is very correct. OP's printer is misconfigured, and adjusting gcode is not the way to fix that.

 

Having the option to enter larger negative numbers could seriously damage printers. I don't feel like being blamed for that.

Edited November 11, 2023 by ahoeben

[GregValiant 1,272]

@Tooth - "i use an Ender 3 V2 and the Z offset that i store directly on the printer gets reset to 0 every time i restart the printer."

 

Within the LCD menus do you have "Save Settings"?  After setting the Z-offset in the printer have you used "Save Settings" (if it is available).

If you don't Save Settings (M500) then every change made to printer settings is temporary and resets when the power is cycled.

[Tooth 0]

I'm Toothless....i mean speachless. Thanks for the effort @Slashee_the_Cow.
Unfortunately, the script is not working yet for me. If i place it in the right folder it does not how up in "Extensions > Post Processing > Modify G-Code".
Attached the Error log

 

 

 

@ahoeben yeah i know its misconfigured, but i can not configure the offset on the printer itself as the value i type in resets itself every timer i restart the printer.

 

@GregValiant yes, thats what i meant with  "Trying to save the offset on the printer does not change anything.". Normally i set the z offset on the printer, use the save button and next time i start the printer this value is available.

 

Edited November 11, 2023 by Tooth

[Slashee_the_Cow 295]

I think I see the problem - you're running a pretty old version of Cura which probably doesn't use a new enough version of Python to support f-strings. Here's a version of the script which uses good old string concatenation (say that five times quickly). Anyway, see if this works.

 

Edited November 11, 2023 by Slashee_the_Cow
removed attachment because it has bugs

[Slashee_the_Cow 295]

Here's an updated one: fixes a couple of important bugs I noticed (was affecting Z moves during relative positioning and messed up comments so they became part of the command which made it invalid)

ZOffset.zip

[Tooth 0]

Thanks a lot again, now it is working. I still got an fatal error with Cura 4.8.0 but i just downloaded Cura 5.5.0 and now it seems to work like a charm.