Welcome to the SeeMeCNC Community

Yeah, I really should have gone with the Kraken, even if I were planning to use only two materials... unfortunately, I now have 2 v6 E3D's. I was really looking forward to having the option to use support materials, very bummed about that. The offsets are pretty much dead on, but the levels are impossible.

One gotcha is if you don't set one of the extruders at 0,0 and you don't set the homing to back off sufficiently from the endstops after it completes, you end up with the entire build surface tilted, because some of the arms cannot move up far enough to accommodate centering the selected head.
Either set the backoff amount high enough to accommodate or set extruder 1 to 0,0 and only adjust the offset of extruder 2 then make sure you have extruder 1 selected when homing.

Maybe that's my problem. I'm not sure what you mean by setting the homing to back off though. I believe the first hotend is at 0,0, and when I switch to the second, it shifts to the same spot (tested by marking a dot on a piece of paper, placing it under the first nozzle, then switching extruders). When I home all seems fine... it goes to home, then shifts in place.

There is a firmware setting in configuration.h, it sets how far off the endstops the carriages move after homing. If it isn't high enough some of the carriages can't move up when centering the selected Hotend after it homes and when it shifts position it ends up with some of the carriages incorrectly offset, so subsequent moves are not in the correct plane.

The constants in question are named ENDSTOP_X_BACK_ON_HOME etc, they are not available in the EEPROM, I have no idea what the default value for the seemeCNC firmware is.

My Hotend offsets are +533,+533 and -533,-533 and I need about 10mm offset after homing to accommodate the shift.

Ah, gotcha, thanks. Do you think it could still be the problem, considering it homes each time it moves to a calibration point? There wouldn't be that shift you mention on subsequent moves, since the first move is from the home position, right?

My offsets are about 11.3 x whatever the steps are set to (I think something like 96steps/mm).

Did anyone manage to get the dual extruder setup to work? This looks like a really nice design

Thanks for the setup, it's working like a charm