Thank you for your in-depth answer. Sorry I haven't replied earlier. I haven't been able to work on this for a few days.
Regarding this question you asked me:
Now, as far as when you unselect T2, do you still have it as "G1 X-75 U365 F6000" OR "G1 H2 X-75 U365 F6000" ? I tested my tfree2.g by having it go a few mm off the homing position, and it worked as expect (i.e. it went to U365 and NOT U368.7).
At the time you asked the question, my tfree2.g was like this:
G91 ; relative axis movement
G1 Z3 F500 ; up 3mm
G90 ; absolute axis movement
G1 X-75 U365 F6000 ; park the X and U carriages
However, I have just tried playing around with the U value of the G1 command and found that with U215, after unselecting T2, the U carriage moves to its parking position and reported position is U=365. i.e. works correctly to me.
My possible explanation for this is that this command in tfree2.g is executed still with the offsets applied. As a reminder, my G10 command for T2 is: G10 P2 X0 Y0 U-150 Z0. So, 215+150= 365.
Also, I haved tried adding the H2 parameter on tfree2.g but the carriadges kept crashing onto the ends. I guess that by playing around a little I would have found a value that also ended up with the carriadges parked in the correct position, but went the other way instead.
I think I am going to leave it like this for the time being.
Also, I have another question. In my tfree2.g, Z is raised 3mm. The machine does so correctly. However, after finishing releasing T2, it moves the Z back down. Is this something done automatically by RRF?
I made some experiments where the nozzle is swapped upside down so that gravity cannot pull out a string.
My theory is, that with retracting, some air gets inside the hotend which is caught by surrounding, sealing melt and warmed up then, pressurizing the melt again. Therefore my strategy would be a fast, short retract of about 1mm to remove printing pressure, followed by a very slow retract (for about 15-30sec with about 0.5mm/min and step-wise descending speed) after swapping to the experimental idle position, which should compensate expansion of trapped air or outgassing moisture/other fumes.
I already did some tests with a macro and it reduced the length of the emerging string significantly (about 3mm instead of >10mm) but still not 100% and therefore, I will do some further testing in the next few days.
OK, so I got the ooznest workbee firmware and web interface working and sucessfully was able to set the 0,0,0 location for my workpiece.
Now what I would like to do is be able to tool change and set the new z=0 value for the new tool. Obviously, now that I have machined stock, I can no longer use my probing piece that I set on the corner of my stock when I started.
I assume that after I setup the initial tool on top of the workpiece, I will have to move my probe calibration plate to directly on the table, probe a point, store and store the offset so I can recalculate Z for the second tool.
When I change tools, I would probe the calibration plate and recall the offset from the original and apply it to the second tool. I have no clue how to do this.
@dc42 I will upload a video this weekend of the material change in process, so that everyone can see where the issue lies and better understand how the mechanical side of my filament selector works.
On another note, Thank you for always being so attentive to this forum! I don’t think I’ve ever posed a question that you didn’t have some input on. I really appreciate that!