Drive 3 is slower as drive 2 at homing in Z [Solved]

dc42

I'm glad you solved it.

The homez.g file you posted earlier starts like this:

; homez.g
; called to home the Z axis
;
; Drive 0 as X
; Drive 1 as Y
; Drive 2 as Z -> 1st Z-motor (left one, viewed from ahead) which is normal Z
; Drive 3 as U -> 2nd Z-motor (right one, viewed from ahead) which is now U
; Drive 4 as Extruder

G91 ; relative positioning

M584 Z2 U3 P4 ; Split Z into 2 (Z+U)

Are you saying that putting the M584 command before the G91 command is what fixed it?

thwe

@dc42 said in Drive 3 is slower as drive 2 at homing in Z [Solved]:

I'm glad you solved it.

The homez.g file you posted earlier starts like this:

; homez.g
; called to home the Z axis
;
; Drive 0 as X
; Drive 1 as Y
; Drive 2 as Z -> 1st Z-motor (left one, viewed from ahead) which is normal Z
; Drive 3 as U -> 2nd Z-motor (right one, viewed from ahead) which is now U
; Drive 4 as Extruder

G91 ; relative positioning

M584 Z2 U3 P4 ; Split Z into 2 (Z+U)

Are you saying that putting the M584 command before the G91 command is what fixed it?

Yes, before "G91" as first line.

dc42

That's very strange, because I can't see any possible mechanism for the order of G91 and M584 making a difference. Are you sure that you didn't change anything else?

thwe

Actually, yes, but I will reset it for safety's sake again to reproduce the funny behavior
At the Weekend i will give feedback

dc42

Thanks, I'll wait for that feedback before I do the 2.02 release in case we can identify something that needs to be fixed.

thwe

So, tested again:

Turn on Duet Wifi - homez.g as in the appendix
G28 Z (via Button Home Z in the DWC)
Homing OK!
Moving in Z: G1 Z-10 (via button in the DWC)
G28 Z (via Button HomeZ in the DWC)
Homing OK!
Moving in Z: G1 Z-10 (via button in the DWC)
Edit homez.g -> set a semicolon before M584 P4
G28 Z (via Button HomeZ in the DWC)
Homing NOT OK! -> U slower as Z
Moving in Z: G1 Z-10 (via button in the DWC)
Edit homez.g -> delet Semicolon before M584 P4
G28 Z (via Button HomeZ in the DWC)
Homing OK! -> U as fast as Z

Thus, it is certain that only the first line of content "M584 P4" in homez.g prevents the strange behavior of the different speeds.

Only valid if the z-axis has already been homed. After a new start or reboot, the FIRST homing will always work, whether with or without the above line, until the second homing occurs.

for safety's sake again here my config.g
0_1542973940030_config.g

... and here the homez.g:
0_1542974052538_homez.g

deckingman

@thwe

Thomas,

I'm glad that you've found a cause and a work around. No doubt David will look further into the cause and come up with a solution in the firmware.

dc42

@thwe said in Drive 3 is slower as drive 2 at homing in Z [Solved]:

So, tested again:

Turn on Duet Wifi - homez.g as in the appendix

G28 Z (via Button Home Z in the DWC)

Homing OK!

Moving in Z: G1 Z-10 (via button in the DWC)

G28 Z (via Button HomeZ in the DWC)

Homing OK!

Moving in Z: G1 Z-10 (via button in the DWC)

Edit homez.g -> set a semicolon before M584 P4

G28 Z (via Button HomeZ in the DWC)

Homing NOT OK! -> U slower as Z

Moving in Z: G1 Z-10 (via button in the DWC)

Edit homez.g -> delet Semicolon before M584 P4

G28 Z (via Button HomeZ in the DWC)

Homing OK! -> U as fast as Z

Thus, it is certain that only the first line of content "M584 P4" in homez.g prevents the strange behavior of the different speeds.

Only valid if the z-axis has already been homed. After a new start or reboot, the FIRST homing will always work, whether with or without the above line, until the second homing occurs.

for safety's sake again here my config.g
0_1542973940030_config.g

... and here the homez.g:
0_1542974052538_homez.g

Thanks!

Does it still work if you exchange the M584 P4 and G91 commands?

thwe

@dc42 :

Thanks!

Does it still work if you exchange the M584 P4 and G91 commands?

Yes, it does not matter if the M584 ...command comes before or after the G91 - with it work

thwe

@deckingman said in Drive 3 is slower as drive 2 at homing in Z [Solved]:

@thwe

Thomas,

I'm glad that you've found a cause and a work around. No doubt David will look further into the cause and come up with a solution in the firmware.

I think so too, but the importance is not so high for this problem - who needs homing after a homing

deckingman

@thwe said in Drive 3 is slower as drive 2 at homing in Z [Solved]:

@deckingman said in Drive 3 is slower as drive 2 at homing in Z [Solved]:

@thwe

Thomas,

I'm glad that you've found a cause and a work around. No doubt David will look further into the cause and come up with a solution in the firmware.

I think so too, but the importance is not so high for this problem - who needs homing after a homing

Actually I quite often home Z repeatedly. I often swap hot end assemblies which changes the offset from the nozzle to the probe and find that the easiest way to adjust is simply to home Z, then raise the bed until it grips a thin piece of paper, edit the offset and re-home, repeat as necessary. Admittedly I haven't had the problem you had with multiple screws but someone else might in the future so it's good to find a solution, even if it might seem to be a small and rare problem.

dc42

@thwe said in Drive 3 is slower as drive 2 at homing in Z [Solved]:

@dc42 :

Thanks!

Does it still work if you exchange the M584 P4 and G91 commands?

Yes, it does not matter if the M584 ...command comes before or after the G91 - with it work

Thanks, I believe I've found the cause and I will implement a change in 2.02RC5 that I hope will fix it. It's to do with what happens when in M584 you reassign a driver to an axis that is initially not visible.

thwe

@dc42 : Unfortunately the update to 2.02RC5 has brought no solution, it has even become worse.
After start or reboot the z-homing is ok, every further homing now always runs with the mentioned problem, no matter if with or without "M584 P4" and whether before or after the G91

dc42

@thwe, I'm sorry to hear that. Added to my list to investigate again.

thwe

Thanks for the effort.
I'm now back to 2.02RC4 to take the next steps, it's not rushing.

thwe

@dc42 :
today the firmware update on RC6 made -> homing (speed of both drives) is now ok

dc42

Thanks for confirming this. I'm sorry it took me a while to get it right.