It's been a while since I've played with the Axis, but yesterday I replaced a few last parts - and got things back to a point where I'm happy enough again. I thought I'd just post everything I've done (and do) in one thread for reference for others.
* Adjusting Eccentric Guides - my most important piece of advice in my mind: MANY SUPER TINY ADJUSTMENTS!!! Really, I barely move the eccentric guides after I've got the rough adjustment dialed in. Rough adjustment to me means the X-Axis Base Plate, Y-Axis Print Head, and the Z-Axis Gantry all don't have any play in them but still move freely. From there it is a LOT of TINY adjustment to dial it in and get rid of any wobble or play while remaining easy to move - I use PTFE grease on all the rails/edges in contact with the guides - no idea if it helps or not - but works for me. I use a bright light above the Axis and then a piece of white paper's edge to verify if things are moving in a straight line consistently. I use the "Move Axis" menu commands to move things back and forth.
* Z-Axis Wobble - the original setup (265mm threaded screw, 5x8 plastic coupler, and gantry nut) had been working fine for me after a TON of tiny little adjustments on the gantry guides. Then sometime in November I did something that caused an 8mm sine-wave on the Z-Axis that I could not get rid of. I'm not sure what happened really - replaced couplers and nuts and threaded screws with lots of options to no avail. I had ordered a couple of custom sized 265mm screws from AliExpress and those came in a couple weeks ago and put those on along with a new style of coupler from Befenybay and then tried several nuts until I found one which was mostly tighter/less rickety than the rest. That got my Z-wobble mostly taken care of - definitely not as straight as it was there for a while, but so much better than it has been the past couple of months. I'm not using the top bracket at all.
* Bed Level - here it was a simple fix. I added 10mm spacers (like what connects the heated bed to the base plate except without any screws at the half-way points on all four sides. Now I have a very level bed with just a little bit of a +.5 to -.5 "top" to "bottom" ... so much better than the +1.9 to -1.3 between all the corners side-to-side and middle of the bed... it was all kinds of skewed before those and made getting a good first layer impossible with various too high and too low points.
* Bed Mesh - I changed Configuration.h to a 7x5 mesh. I don't know if any of the measurement points are over magnets, but I'm happy right now, so not worrying about it more.
* Bed Skew Correction - after I ran my general setup procedure below the first time, I printed the Bed Skew Measurement Squares (I used one which was an all-in-one bed skew measurement cube to make the printing easier (if not more PLA use)). I make the changes in Configuration.h to enable it and calculate the values. Now with the Bed Leveled and Skew Corrected, I run the setup procedure (starting at Step 6), and I'm very happy with my first layer results.
* Extruder Steps/Flow - I've been noticing that tuning Extruder Flow set to 110 gives better results. To be clear, I never used the new Configuration.h change of DEFAULT_AXIS_STEPS_PER_UNIT to 85 from the initial 98. I tried 85 and I was under extruding, so changed it back to 98. I'm assuming by changing it to 110 in the Tuning menu - I likely should just use 108 instead of 98 in the Configuration.h file. You can't Store the Extruder Flow Tuning - so changing in the Configuration.h is probably the right thing to do.
Z-Height and Bed Leveling Procedure
Lastly, I'm including my Bed Leveling and adjustment setup that I go through whenever I change something.
1) With power on and the flex plate on (or whatever you're going to print on)
2) Disable all the steppers (in OctoPi for me, Prontoface works, maybe M18 works)
3) Manually position the hotend in the center of the plate on the X and roughly 5cm "south" of the center of the bed on the Y by hand
4) Lower the gantry down by hand until either the hotend is closer than 1mm (I use a .6mm feeler gauge myself; or the inductive sensor lights up.
5) Adjust the sensor up/down until the head is <1mm, and >.5mm (roughly .6mm for me is what I've been using) and the sensor light is just turning off/on with any gantry up/down movement in that 0.5-1mm range.
--- Above after physical changes to inductive sensor; below for just about anything other changes ---
6) M502 to reset all the settings to factory, M500 to save them.
7) G28 to Home all axis
7b) OPTIONAL: Recently I've been running this autoleveling with a 160-degree hotend and 60-degree bed; I first raise the hotend by 20mm to ensure I don't melt the sticker on the flex plate; then set the temps to 160/60 (M104 S160, M140 S60) and and wait for the temp to come up before Step 8.
8) G29 to run the 7x5 autoleveling
9) M500 to save the mesh
10) G28 to home all axis (If heated in 7b, I put a once folded piece of paper under the center homing spot so the heated hot end doesn't sit too close to the flex plate sticker - and try to go fast!)
11) M420 S0 to turn off the level/fade
12) M114 to make sure I'm at Z0.0
13) I use OctoPi (technically OctoPod on my iPhone) to move down 0.1 (G91, G1 Z-0.1 F720, repeat up/down, G90) at a time until a once folded piece of paper is just starting to grip well but not completely STOP the paper from moving under the nozzle. This is often -0.2 to -0.5 when checked with M114 again.
14) M206 Zx.x to store the value. As I said, I often end up with this being "M206 Z0.3" ... NOTE WELL the lack of a (-) negative sign. I missed this the first couple times and that was why my Z was too high.
15) M500 to save everything
16) I generally turn the power off and unplug the OctoPi at this point, and wait couple of seconds and then turn everything back on
17) I start printing a 50x50x0.2mm square that I use for this to set my Z-Offset
18) Even at the skirt, if I see it not sticking or too thin, I click the LCD selector wheel, go to into Tune on the menu, then Z-Offset and start going negative. Past couple of times I've needed to go to -0.200 or -0.300 to get a good squish. I also change the Extruder Flow to 110 up from 100 recently (see above note).
I hope some of these things help folks! -- Jay