I am currently fiddling around with multiple Hotends and discovered, that the setting “extruder z-offset” doesn’t do anything in response on my printer.
For example, neither:
extruder.EXT1.z_offset 1
nor:
extruder.EXT1.z_offset 50
does anything to my printjob, it just prints as if the setting isn’t even there.
Do I have to take something additional into account for using extruder z-offsets?
Extruder height isn’t set via z_offset but relative to the axis’ end, see http://smoothieware.org/gamma_max for several methods for doing so.
But I don’t want to set a home-position, I want to set an offset to it. I already have my first extruder (EXT0) set perfectly in height. But EXT1 has a different height at home-position than EXT0, lets say EXT1 is 1mm higher than EXT0. Now I have to tell smoothieware, that EXT1 needs to get 1mm closer to the bed than EXT0. “extruder.EXT1.z_offset -1” looks like the way to go, but it doesn’t do anything in response.
I renamed the extruder modules to T0/T1 etc to maybe match the tool identifier. Didn’t help. A bit strange: I can’t find a single result with google that ANYONE is even using the extruder z_offset setting at all. Does it even work in general? Or do I have to blame my google-skills?
Though I am not that good at coding, I took a look into smoothie-source and it seems, that the z_offset is at least programmed in at every place where x&y offsets are mentioned. But I am not even close to sure, that I checked this correctly.
Additionally, I tried using the gCode-command “G10” (tool offset), because I saw it mentioned in the source. Didn’t work either 
I changed X&Y offsets of each of mine extruders like I did with the Z-offset before. They all work. I tried both, positive and negative values. Every time I get a different position, according to my set offsets. Only Z-offset doesn’t work. Because of working X&Y-offsets, I can probably rule out user-error. Shall I open an issue thread at GitHub about this, @Arthur_Wolf ?
z_offset means nothing to smoothie, it’s fully ignored. you are pretty much the first user in 5 years to have hotends that are not at the same z height ( that I know of ) if that’s really what’s going on here. is it ?
But I am definitively not the first having problems with this. But for smoothiware “fully ignoring” this, the command z_offset is mentioned everywhere with X&Y offset in the source-code 
It should be easy to activate this if it is already written in, or not?
@Rene_Jurack So far users who mention z_offset are actually users trying to do what is described on the gamma_max page ( which is why I pointed you to it initially ), I really don’t know I’ve seen a user with different z positions for different hotends before, you are at the bleeding edge here.
I don’t think anything except the setting is written in the code for this.
I already tried G10, doesn’t do anything for Z, too.
I just mentioned a bounty at github, maybe someone gets motivated by it. And if not, it fixes a bug for a good firmware that I use daily. win win 
How about M218?
Might be XY only though.
I looked through the gcode/mcodes, and tried G10 and M206. Both didn’t work with Z on smoothie like I want them to.
The thing is, if you look for “x_offset” or “y_offset” in the sourcecode, everytime the parameter “z_offset” is mentioned, too. With code, math etc… I think, it is just left out in one of the last calculations…
Just thought I’d mention that if the nozzles are fixed in relation to each other, when the higher nozzle is used, the lower nozzle will drag through the print and mess it up. For dual extrusion I’ve always had to set them the same.
Also you might be able to get around it by using a tool change script that puts the machine into relative mode, use g92 to shift the offset, and put it back into absolute mode
No, sadly not. Fixing this through a toolchange script does only work for the layer where the toolchange happened… The following layer has an absolute Z-height and gets squished or stretched.
Different heights of the toolheads is no problem with my setup.
Obviously you would need to do the tool change script to shift the offset back using G92 every time you also switch back to the first head too.