Error 04125 at first MMu homing

[FelixGraf404]

Hey,

I have the problem that the MMU3 (Ultimulti) with the firmware >= 3.0.0 do an strange rattle noise and can´t reach the homing Position for the Idler.

Change the sensitivity (4-7) in the threshold menu do nothing, same prob again.

The idler can move free, nothing blocked. The "endstop" of the idler part is reached perfect.

Have no idea to solve that problem. At the moment i use firmware 3.12.2/1.0.6 without problems.

[davidkerny]

Hi Felix. I have encountered something similar as you describe, after tinkering with the Idler TMC sensitivity and homing speed registers, via G-codes. I probably managed to mess up come contents of the EEPROM and the MMU unit was no longer able to even start homing the axis. What helped was to perform a factory reset: https://help.prusa3d.com/article/factory-reset-mmu_510075

Could you try the factory reset to see if it helps?

The FW 3.0.2 is miles better than 1.0.6 - it would be a shame to have to use the 1.0.6 nowadays. The idler sensitivity Tune menu should be able to sort out any of the problematic Idlers. Some other possible causes might be the hardware ones: idler coupler not being tight or aligned properly, idler tension too high etc.

[FelixGraf404]

Hey David,

Thanks for your fast response,

I put the 3.13.2/3.0.1 combo on my Printer and dis the reset Like in the PrusaHelp Page.

But the Problem come back. The idler Rattle Like before (sensitivity 4-7) did nothing.

Tension and Position I have Double checked. > ok

Idler rotates free

Is it possible That the idler Motor reports wrong currents?

Before upgrading to mmu3 the mmu2s (and the Motor) sometimes Choosed the wrong color. The Display Showed Color 1, the Mmu physical use color 2 f.e.

[davidkerny]

@FelixGraf404 Hi! In the cases I have seen so far, similar issues were caused mostly by hardware faults such as

1. wobbly Idler without the metal coupler that didnt rotate properly,
2. idler being pushed to the side so much, that it was hard to move it,
3. foreign object causing the idler not to rotate properly or similar.

There has been edge-cases reported of Idler stalling when rolling over the filaments - which might lead to MMU selecting a different color by accident. But if your idler doesn't home with any of the sensitivity settings (sg_threshold 4-7), it is weird. So far, it seems that one of these settings should work on any machine. Can you maybe make a detailed video of the MMU while malfunctioning? In case we find out what's wrong and what helps in this case, I can share the findings with the developers to evaluate them.

The idler currents are set to produce the correct amount of force with the exact type of the motor as there is on the Idler / Pulley / printer's Extruder. If you use a different type of motor, it might not work correctly. In case there is a problem with the electronics, such as a TMC malfunction, the firmware 3.0.0 and up should notify you about something being wrong. (TMC not responding, reset, overheat, communication error, undervoltage error etc.). If there was no such error screen, I would assume there might be a hardware error.
In case you have used an original prusa MMU3 upgrade kit, you might also try to reach out to prusa support to see if they can provide an insight.

[FelixGraf404]

https://github.com/davidkerny/BUZA-ULTIMULTI/assets/105812017/74bba0c9-a2fb-4557-a465-4824fcc4c0e0

The idler rotates Sweet Like Butter. (Vid1)

My Setup:

Fystec Mk3s clone The Mmu was an fystec mmu2s, the Upgrade Kit is an original Prusa Kit (The present Poor Student wanna Print, so he has to but fystec stuff 🤪)

The error:

https://github.com/davidkerny/BUZA-ULTIMULTI/assets/105812017/e68e1e90-2c43-40e6-8018-f59c4e8ee1af

https://github.com/davidkerny/BUZA-ULTIMULTI/assets/105812017/528459b4-9c8b-4f2c-a9fd-192a58bb0043

I never get Any TMC errors

[davidkerny]

Hi! Your Idler motor seems to be a bit larger than usual. It is possible the homing just requires some more tuning to fit your hardware. Some of the larger motors have been reported to work with low stallguard threshold numbers such as 2.

To set the Idler homing stallguard threshold to 2, send this G-code to the printer:

M708 A0x19 X2

The value 2 might not suit your unit, but the point is, using a G-code, you can try setting values out of the range available in the GUI ( in the error screen's Tune / Anpassen menu).

---

When looking around for the available options, the TZB firmware seems to home the Idler more reliably using sg_threshold 7 - which is default even for MMU3. It is using a faster homing feedrate though. As a next thing to try, I would suggest trying a faster homing feedrate.

It should be possible to change the feedrate using the M708 command too, see: https://help.prusa3d.com/article/registers-mmu-mmu3_511780 If it doesn't work, you can also try to reach out to the Prusa Github for help.

D.

[FelixGraf404]

Here is the log after set "M708 A0x19 X2": (The sensetivity was 19 After That command, the problem still exist)

M708 A0x19 X2_ LOG.txt

The register MMU link blows my mind, i understand nothing (sorry no Programmer). I dont undedrstand how or which command do an faster homing feedrate :/

[FelixGraf404]

News from my MMU:

I ordered an original Prusa Idler Motor, installed him an the mmu homes With no Problems. So the "tuning" of the Motor Parameter should be the key of the Not Home Problem (#04125)