G30Auto-Tilt creates hidden Z-offset-Duet 3-3.0RC2, DSF1.2

Luke'sLaboratory

@Luke-sLaboratory
Update:
Tested out on a non-print using the G30 Bed Tilt -

It definitely adds 5mm invisibly somewhere.

I just ran these commands:

M561 ; clear any bed transform
M558 P9 C"io7.in" H10 F120 T3600 S.05 A2 ; Ensure that Dive Height is safe for Bed Tramming
G1 X270 Y570 F7200 ; Move Fast to next spot
G30 P0 X270 Y580 Z-99999 ; probe near a leadscrew
G1 X10 Y136 F7200 ; Move Fast to next spot
G30 P1 X0 Y136 Z-99999 ; probe near a leadscrew
G1 X560 Y136 F7200 ; Move Fast to next spot
G30 P2 X580 Y136 Z-99999 S3 ; probe near a leadscrew and calibrate 3 from the 3 motors
M558 P9 C"io7.in" H5 F120 T3600 ;Sets Smaller Dive Height for Mesh Calibration (SPEED, have tried disabling this just in case this isn't a good use of it)
G1 X322 Y322 F7200  ; recenter fast
G28 Z	; Rehome Z | Diagnostic to see if G30 motor calibration was "overcorrecting"

And when I sent G1 Z0, there was still 5mm of gap between where the machine thought it was 0 and the actual bed.

Looks like there's something goofy afoot!

Luke'sLaboratory

Alright -

To prove I'm not insane, I took a video that shows in its entirety the process I'm doing and the error I'm seeing. It shows that before I use any kind of adjustment, The z-axis homes and G1 Z0 takes the nozzle right to where it should be. However - Once I use G30 OR G29 (I just show G30 S3 in the video) I get a hidden Z-offset that the machine has NO idea what to do with, even after rehoming, not only with G28Z (calling Homez.g) but also a regular G28 that homes all axes.
VIDEO
https://youtu.be/tdWajc_Q3ks

Thank you!

gtj0

I'm having problems as well, maybe not exactly like yours but similar.
What's your homez.g file look like?

Luke'sLaboratory

@gtj0 in that video it was just a simple drop bed->probe center

G91                  ; relative positioning
G1 H2 Z5 F3600       ; lift Z relative to current position
G90                  ; absolute positioning
G30 X322 Y322                   ; home Z by probing the bed

Reviewing the tape looks like its been ignoring my instructions to go to center
Still goofy as heck!

gtj0

The only thing I noticed in your config was that the Z "jerk" (M566) was really low (9.00) when it should probably be between 300 and 600. That would only really affect height map correction though.

I do have something for you to try...

It's almost as though the G1 Z0 in your macro is resetting the internal position but the move isn't actually being executed. Here's a few things to try...

Start with a reset so the axes aren't homed
Don't do a bed levelling
Remove the X322 and Y322 from the G30 command in your homez.g
Add a M400 and G1 Z0 (in that order) to the end of your homez.g
Move Z away from the nozzle with a G91 ; G1 Z5 ; G90 (just in case)
Home XY
Move XY to the center G1 X322 Y322
Just do a home Z without your macro
See what happens

Luke'sLaboratory

@gtj0 Yep - as you can see I'm still fussing with my Z-axis motion so I keep jerk low to ensure I'm not causing other issues.

I'll give it a shot when I have my machine back together - parts arrive this afternoon to get rid of that wobble/Noise

It will be noted that when I home at any time (with Homeall OR homeZ) before any compensation it homes perfectly and G1 Z0 will correctly move my nozzle to the correct height. Once correction is run, I need a full reboot.

Thank you!

Phaedrux

M566 Z9 is in mm/min, which is 0.15 mm/s which might actually be causing you more issues than you're trying to prevent because any time you try to perform a coordinated move with the Z axis it will slow to a crawl at the start of the move.

I'd suggest a minimum of M566 Z60 which is 1mm/s.

Not saying it's related to your current issue, but it could manifest itself in other odd behaviour.

Luke'sLaboratory

@Phaedrux
Default config gave me 12mm/min, If cutting defaults by 25% were to cause other issues, that's just weird.

I'm confident once I get my mechanics figured out (been swapping parts most of my afternoon) i'll increase everything as much as possible, but I took a modest reduction from defaults given by reprapconfig tool.
As an addendum - the machine prints correctly, but ONLY if i haven't used G29 or G30. G29 I could see maybe having something to do with it not allowing such small changes very quickly (like off of a very crazy mesh) but G30 lead screw compensation doesn't introduce any of those issues.

Once i get my machine back together, I'll try out out your and gtj0's suggestions.

Phaedrux

@Luke-sLaboratory said in G30Auto-Tilt creates hidden Z-offset-Duet 3-3.0RC2, DSF1.2:

Default config gave me 12mm/min

The default is set purposely low to prevent any damage since it has no idea what your Z axis configuration is like, so it's already being ultra conservative on your behalf. It's up to you to tune the machine with reasonable values, as I'm sure you will.

Mesh compensation is one case where low Z axis jerk causes issues because the Z axis needs to respond to changes in height in a coordinated manner with the X and Y axis. This usually presents as stuttering X and Y motion as it pauses to let the Z axis catch up. This will depend a lot on your first layer print speed and X Y jerk and acceleration as well.

There is likely other things at play though with the mesh compensation issue. Without seeing more details I couldn't say what. RRF3 is still in its infancy, so there could be a bug, or it could be configuration issues, or both.

Luke'sLaboratory

@gtj0 @Phaedrux

I've updated my config with a higher M566 value (60) and I've done the simpler Z-levelling procedure proposed by gtj0.

If I don't do any sort of bed adjustment/mesh, I don't have any issues. His procedure works exactly as expected, Z0 is actually Z0. I then did the exact same thing, just with using bed compensation (auto-tilt), got rid of the scripted G28 Z and did a manual rehome, with the same G1 X322 Y322 and G28 Z from console, and got the same offset.

I firmly believe this is some kind of bug somewhere.

gtj0

@Luke-sLaboratory said in G30Auto-Tilt creates hidden Z-offset-Duet 3-3.0RC2, DSF1.2:

@gtj0 @Phaedrux

I've updated my config with a higher M566 value (60) and I've done the simpler Z-levelling procedure proposed by gtj0.

If I don't do any sort of bed adjustment/mesh, I don't have any issues. His procedure works exactly as expected, Z0 is actually Z0. I then did the exact same thing, just with using bed compensation (auto-tilt), got rid of the scripted G28 Z and did a manual rehome, with the same G1 X322 Y322 and G28 Z from console, and got the same offset.

I firmly believe this is some kind of bug somewhere.

This is going to be way overkill, but try adding an M400 after every command in bed.g, homez.g and any other .g file involved except config.g. I'm trying to see if there is a code buffering problem where codes are not executed fully or executed out of order. Both have been issues in the past.

Luke'sLaboratory

@gtj0
Ok will report back once my print is finished.

Luke'sLaboratory

@gtj0
Tried it - Same result. Put a M400 in erry macro, command, etc I could think of. My print executed perfectly.

gtj0

@Luke-sLaboratory said in G30Auto-Tilt creates hidden Z-offset-Duet 3-3.0RC2, DSF1.2:

@gtj0
Tried it - Same result. Put a M400 in erry macro, command, etc I could think of. My print executed perfectly.

Hmmm. I may have lost track somewhere.... Under exactly what conditions did it work perfectly?
With the addition of the M400s in your original macros/process that did cause the offset, did you get the 5mm offset?

The purpose of the M400 is to cause the firmware to wait before the previous moves are done before proceeding to the next command. I was hoping that adding the M400s would fix any issues with the buffered commands not being executed correctly.

Luke'sLaboratory

@gtj0

Sorry for lack of clarity.

There was zero change in the behavior I was describing. I still experience the hidden offset when I use the bed levelling features, even with M400 after every line in any positioning macro, custom or default.

If I do not use the bed-levelling features, My printer performs flawlessly and creates excellent prints, and my homing procedure (both homeZ & Homeall) functions correctly.

gtj0

Weird. The only difference between your process and mine is that your bed levelling starts at the middle rear and runs counter-clockwise. Just for the fun of it, what happens if you start at the front left and go clockwise?

Luke'sLaboratory

@gtj0
I'll give it a shot. As a comment, this also happens when I use g29 for mesh levelling as well, it's not confined to just g30.

Hopefully something works soon!

Luke'sLaboratory

@gtj0

Alright - Just tried out the switch - still no dice. The reported Z0 even after i do a full G28 rehome still floats wayyyy above the real 0. However, I reset the board (not a power cycle, just the reset button) rehomed, and the offset went away and its currently printing a perfectly adhered print.

This is honestly pretty frustrating

Luke'sLaboratory

@gtj0 More Shenanigans, still really stuck where to go with this.

I am now using 3.01 beta, and have copied over a 4-point conditional levelling loop from @kraegar to take my hands out of it.

; bed.g
; called to perform automatic bed compensation via G32

M561                         ; clear any existing bed transform
; If the printer hasn't been homed, home it
if !move.axes[0].homed || !move.axes[1].homed || !move.axes[2].homed
  G28
  
M558 P9 C"io7.in" H15 F240 T6000 S.05 A1 ; Ensure that Dive Height is safe for Bed Tramming

;Run initial 4 point leveling routine
G30 P0 X30 Y30 Z-99999
G30 P1 X30 Y540 Z-99999
G30 P2 X480 Y540 Z-99999
G30 P3 X480 Y30 Z-99999 S3



while true
  if iterations = 5
    abort "Too many auto calibration attempts"
  if move.initialDeviation.deviation < 0.01 
    if move.calibrationDeviation.deviation < move.initialDeviation.deviation + 0.005
      if move.calibrationDeviation.deviation > move.initialDeviation.deviation - 0.005
        break
  echo "Repeating calibration because initial deviation (" ^ move.initialDeviation.deviation ^ "mm) must be < 0.01"
  echo "and (" ^ move.calibrationDeviation.deviation ^ "mm) must be within 0.005 of initialDeviation"

  M558 P9 C"io7.in" H5 F180 T6000 S.05 A2
  G30 P0 X30 Y30 Z-99999
  G30 P1 X30 Y540 Z-99999
  G30 P2 X480 Y540 Z-99999
  G30 P3 X480 Y30 Z-99999 S3

echo "Auto calibration successful, deviation", move.calibrationDeviation.deviation ^ "mm"
echo "Auto calibration successful, initialDeviation", move.initialDeviation.deviation ^ "mm"  
    
G28

However - it completely ignores the loop, does the two iterations, doesn't echo anything, and then re-homes.
I'll ignore that part of it for now.

Here's the readout from the two iterations:

1/18/2020, 10:45:28 AM	Leadscrew adjustments made: -0.060 -0.043 -0.002, points used 4, (mean, deviation) before (-0.033, 0.171) after (0.000, 0.170)
1/18/2020, 10:44:30 AM	Leadscrew adjustments made: 2.184 2.030 1.998, points used 4, (mean, deviation) before (2.051, 0.174) after (-0.000, 0.152)

The key takeway i think here, however, that while the first iteration shows that its level, the bed thinks that its ~2mm off on ALL axes, then corrects for it. The second iteration has the same deviation from the mean, but is VERY close to this new mean.

When then G28 completely rehome (using the same damn probe), it floats this ~2mm above the middle, which i proved out by manually disabling limits and moving the bed up in .05mm increments till it touched the nozzle. I think this has to be something derpy in the firmware somewhere as part of the self-calibration routine. This is AFTER I nuked the pi and re-did the image, so Now i'm going to use the erase feature on the duet 3 and try with 100000000% fresh firmware there as well.

anything else anyone can think of, let me know. I'm stumped.

Phaedrux

@Luke-sLaboratory said in G30Auto-Tilt creates hidden Z-offset-Duet 3-3.0RC2, DSF1.2:

anything else anyone can think of, let me know. I'm stumped.

I think you're on the right track. Nuke it from orbit and have a fresh run at it.