Z probe offset relative to homing, not nozzle?
-
I'm building a printer that's IDEX and has swappable tool heads with varying extruder/hotend setups. The left tool (T0) has the Z probe on it (as specified by the docs) but I'm trying to wrap my head around the G31 Z probe offsets.
It seems that it's expecting it to be relative to the nozzle tip... but this is problematic for my machine as where the nozzle tip is, relative to homing, could change depending on the tool.
For the tools, my plan was to have separate config files for each tool (in each left or right position). When swapping tools I uncomment the appropriate line in the config to specify which tool it's using and where. Those files would contain the
G10 P1 ...command to set the tool offset.
But it would be nice to not have to include a Z probe XY offset in there too - since technically it will not change.Is there a way to specify that the Z probe XY offset is relative to the homing location?
Since the config will have specified where the homing switches are (using
M208) and what the tool offset is (usingG10) it should be able to calculate what the Z probe offset is relative to the nozzle, would it not?I have an E3D ToolChanger and realize now this is technically an issue on that machine too - I have 2 Hemeras and 2 Titans and the nozzle position is different. But the Z probe is fixed on the carriage - so same problem would apply.
Update: Maybe wrong about the TC and maybe my answer... the official TC config specifies no offset at all for the Z probe. So maybe all of that is handled in the tool offset?
https://github.com/e3donline/RepRapFirmware-SD/blob/master/rrf3.x/sys/config.g#L51
-
At the end of your post you have discovered the typical way this is handled - zero offsets for the Z probe and actual offsets for the tools.
Frederick
-
@fcwilt said in Z probe offset relative to homing, not nozzle?:
At the end of your post you have discovered the typical way this is handled - zero offsets for the Z probe and actual offsets for the tools.
Frederick
So, to confirm:
Set the Z probe offset:
G31 P500 X0 Y0 Z2.5
^ I assume I still need to set the Z trigger distance in my case since I'm using a contactless sensor, unlike on the ToolChanger where it's a microswitch. But X and Y are 0, of course.Set the axis min/max so that when the axis is homed, the probe location is at 0,0 on my bed, using
M208Then set tool offsets relative to the probe location, using
G10. Since, in my case, the tool nozzle will be to the left and in front of the Z probe location, that would be a negative offset for both X and Y.Am I off on any of that?
One further point of confusion for me is the offset for the secondary tool - the "U" axis, without the Z probe on it. The docs aren't super clear about what it's offset is relative to... but it doesn't seem that it would be relative to the Z probe 0,0 position.
I'm guessing it's relative to the homing position on that side? So, for example, if the second tool homes to the right and I specify, with
M208that this location is at 350mm on X/U - The second tool nozzle X offset (forG10) Would then be the distance from that right edge, correct?At least roughly - I know I'll need to dial things in.
-
Hi,
Well I setup the M208 parameters I set the min/max values so that X=0 Y=0 is the CENTER of the bed.
But in any case, as I understand it, the tool offsets are relative to X=0 Y=0.
It's easy to verify if the values are correct. With a tool selected then a G1 X0 Y0 should move the nozzle of that tool to X=0 Y=0.
Frederick
