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MMU2 Gets Confused About Selector Bearing Position #1181
Occasionally my MMU2 selector bearing will get confused about its position.
When loading or unloading a filament, the bearing moves to a position which does not engage the correct filament. Sometimes the bearing will engage the wrong filament, causing it to be ejected out the front of the MMU. Other times the bearing will only partially engage or not engage on any filament, causing a load or unload failure.
This happens maybe once every 1000-2000 material changes. When it happens, resetting both the MMU and the MK3 using the reset buttons next to the USB ports will correct the problem. Cycling the power or resetting the MK3 with the front panel button does not reliably fix the issue.
The selector bearing can travel freely to both stops.
The MMU is properly tensioned. The problem is that the selector bearing is not being positioned properly.
For example, I select "Load Filament 2", and the selector moves to the position to accept filament 2, but the idler body moves to engage a different filament (for example, 4). The result is that filament 4 is ejected out the front of the MMU.
This happens only rarely, but when it happens the only reliable way I've found to clear the problem is to reset the MMU and MK3 using the reset buttons near the USB ports. If I simply cycle the power and allow it to rehome, the MMU will continue mispositioning the idler body.
I've had this twice today (first day with the MMU). First time I gave up and powered down.
Second time - I got support involved.
It happened the second time after a filament load/unload issue. This turned out to be a stringing filament under the finda.
The print was a two colour print using 1 and 5. After I cleared the finda - it suddenly gave me a filament load flashing LED on position 5 when trying to load filament 5 - with the selector on position 5 - but with the idler body positioned for filament 1.
We tried a fair number of things - but it insisted on pushing the filament in position one out just like @Blanchard3d pic in comment above.
So - we decided to try one last thing - while the printer was still showing "MMU needs user attention" - I hit the reset of the MMU only.
It reset, selector moved to position 1, and the MK3 suddenly changed back to heating nozzle.
Once the heating was complete - it then pushed the filament out of position 5 with the selector in position 1 and started to beep. But this time the LCD asked me to remove the old filament and then press the knob on the mk3.
I did this - and the unit then did the proper reload of filament 5 (moved the selector to the right place) and the print continued. Still printing now - just hoping it'll complete.
So - I have also seen this, it's definitely that the MMU idler and selector are in disagreement on position - one is one place - the other a different place.
Seems like a definite bug in the MMU firmware.
But - it does seem - as a last resort - that resetting the MMU alone while the printer holds the progress is worth at try - am guessing only as a last resort as I have no idea how reliable this is - but if the print is going to fail anyway - worth a try :)
This happens to me.
It could be solved, I feel, by just homing the drum more often. Maybe every layer?
Similarly, it can lose track of the output selector, and print with the wrong filament. I have this once in a while, though less since I cleaned up the filament paths. Nonetheless, the wrong sized bondtech gears with a single calibration eventually fill the printer with plastic scrap, and causes any number of jams.
referenced this issue
Oct 10, 2018
Saw the same thing. Usually 1-3 moves without an issue, but over to 4 and 5 it sometimes has an issue.
I have experienced this (pulley barrel getting out of sync with the selector) as well twice in the last 24 hours. I was unable to clear it either time. I have the latest firmware installed- 3.5.1 and 1.0.3. Very frustrating to lose prints after a huge time and filament investment. Support suggested downgrading to the previous firmware release . I think that's the standard solution when they are clueless.