Independent Z with Independent Sensors U steps/mm wrong

[LeonMF]

A whole bunch of months ago, I retrofitted my Promega to have dual Z lead screws with independent sensors for homing. Then I had so many issues with the Maestro board skipping steps, the extruder system behaving badly, and a work trip that kept me busy for several months.

I'm back to it now, I've redesigned the X carriage, swapped in a Duet WiFi that I had lying around while waiting for the Duet 3 and I've got everything pretty much back to working but the Z homing is behaving weird.

I set the U axis at the same steps/mm as Z but in the commented out line the U axis gets 837.20steps/mm and E0 gets 420. When use the second option where I try to set U to 400 after the fact, I get U and E as 420.

[0_1567892760893_MonkeyMega-Config-2019-09-07.zip](Uploading 100%)

I'm on firmware 2.03 and, at this point, I'm at a complete loss as to what to do. I can try putting some overrides in the homez file but I'd rather find out if I'm doing something wrong first!

[LeonMF]

Here is a dropbox link to my config:
https://www.dropbox.com/s/a6954n6rumxr327/MonkeyMega-Config-2019-09-07.zip?dl=0

[Phaedrux]

I think you may need to define U in your M584 command? And I'm not sure but I think it should be P4 instead of P3.

I don't personally use multiple independent motors for Z, so I could be wrong.

I'm sure you've seen this, but maybe a good idea to go over it once more and try to follow the examples.

https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors

[fcwilt]

Hi,

That article that Phaedrux referenced makes no mention of creating other axes.

So I think there may be something amiss in your configuration.

Frederick

[Phaedrux]

Just to make it clearer what is happening when homing Z

; homez.g
; called to home the Z axis
;

; ============= PRE-HOMING =====================

; Ignore Machine boundaries
M564 H0 S0

; Turn off bed leveling during homing
G29 S2 ; Does the same as M561!
G29 S2 ; Do it twice because once just isn't enough

; Switch to Origin Tool
T0

; Relative positioning
G91

; Provide Z height clearance
G1 Z10 F250 S1


; =========== Reconfigure axes =========
M584 Z2 U4 P4 ; Split Z into 2 (Z+U)

; =========== set U axis current ======
;M906 U1200 I60; Set motor currents (mA) and idle current percentage


; ============ HOME Z ==============
; Rapid Z+U until limit switch triggers
G0 Z450 U450 F1500 S1

; Back off to release limit switch
G1 Z-5 U-5 F120 S2

; Slow advance to trigger limit switch
G0 Z20 U20 F120 S1

;Offset U before merge to level platform - again
;Offset not needed due to tuned sensor flags.
;G1 U-0.5 F1000

;Merge U and Z again
M584 Z2:4 P3

;Move back again 5mm in -z direction
G1 Z-5 F1500 S2

;Set actual z-height (might be able to do this in config as part of default height.
G92 Z322.3 U322.3

; ============ Post-Homing ==============

; Revert to absolute coordinates
G90

; Re-enable mesh leveling
G29 S1

; Stop movement across limits, enable boundaries, homing requirement
M564 H1 S1
;

[Phaedrux]

The ProMega config setup is a little unorthodox in my opinion. There have been a few other threads trying to sort through it in the recent past.

Have you seen this? https://promega.printm3d.com/documentation/software-firmware/adjust-homing-macros

[dc42]

Check that in config.g you have a M584 command that creates the U axis and also redefines the E drivers, earlier than your M350 and M906 commands. I'm using a smartphone so it's not easy for me to look at the config.g that you uploaded.

[Phaedrux]

I think the problem is that the u axis isn't created until the homing files as it's missing from the m584 in the config.g

[dc42]

@phaedrux said in Independent Z with Independent Sensors U steps/mm wrong:

I think the problem is that the u axis isn't created until the homing files as it's missing from the m584 in the config.g

In that case the U motor will still be set up as an extruder, and the microstepping and motor current will be set as for the extruder. So if E microstepping is different from Z microstepping, that would explain the symptom

[LeonMF]

@phaedrux said in Independent Z with Independent Sensors U steps/mm wrong:

https://duet3d.dozuki.com/Wiki/Bed_levelling_using_multiple_independent_Z_motors

Yes, that's what I based my config on!

[LeonMF]

@dc42 @Phaedrux OK, I can certainly modify my config to create the U axis and then combine them. The posted wiki page doesn't say to do that so I missed the obvious!

[LeonMF]

@phaedrux There's no reason to treat this like a Promega. I've gutted it, changed the Z drive system to dual lead screws, the rails, the carriage, the board, the bed...

[LeonMF]

Defining U in config.g before then combining worked for me. Thanks for the help!

[fcwilt]

@leonmf said in Independent Z with Independent Sensors U steps/mm wrong:

Defining U in config.g before then combining worked for me. Thanks for the help!

Hi,

What is the reason for end stop switches on both z axes?

Frederick

[Phaedrux]

@fcwilt I believe it's used as an X axis leveling mechanism.