Erratic MMU2 - Time to uninstall?
I'm in the same camp as must of us - Willing to wait for the MMU2 to evolve into a more reliable machine. But I am seeing problems now that I would not expect well written firmware to exhibit. Does anyone know what might be going on here?
I will print a single color project. Start the print, it asks which extruder to use, I select one of the extruders. Filament will be fed to the print head. Sometimes, it goes there, the printer heats up, and away we go. Other times, the filament will be fed to the extruder, then retracted, then fed back again, retracted, possibly a few more times, and then I am told the MMU needs attention. A quick unfastening of the MMU lid and the Extruder door to search for strings that are not there. A check for friction in the bowden tubes, a check that the FINDA and IR sensors are calibrated, and finally, another attempt at printing. But this time, watching the sensor info. If I abort the print, usually by power cycling the printer, I can Load to Extruder 100% of the time, with no problems. But, when I go to print, guess what? It retracts the filament again!
I can see the FINDA and IR sensors change to 1 when they should. But again, the filament will be fed and retracted, all the while, the sensors feeding me the expected information. And I need to give attention to the MMU2 again. I have no idea what could be causing this.
I am printing Face Masks for the hospital down the road. The stock MK2.5s is cranking away, but the MK3s/MMU2 is so problematic I'm almost to the point of deciding my production is going to take twice as long. I've REPLACED the E3d extruder, taken the extruder assembly apart and cleaned it, examined everything through a microscope for tiny sources of friction. Checked alignment of the MMU2 rollers. I've made the magnet, and Bowden Tube modifications, I've got the reels above the printer so I don't have to worry about retraction. (I'm down to exclusively single material prints anyhow.)
I've gone from using the MK3s at a moment's notice and the MK2.5s if I had a lot to print at once, to using the MK3s only if I have to. It has so many advantages I wish it were the other way around.
Anyhow, does anyone have any idea why my printer gets in moods where it insists on retracting the filament?
RE: Erratic MMU2 - Time to uninstall?
Sounds like issues with the sensor in mmu selector (finda) or the ir sensor in the extruder.
I don't know if you have MMU2S or not but in my opinion there is not enough feedback from the IR sensor in the extruder, the UI on the display is not always accessible and may not show the changes properly.
I decided to add a led so i have a visual indication regarding the state of the IR sensor and how it triggers, this helps a lot since the adjustment of this sensor can be very tricky.
Like this one:
https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-user-mods-octoprint-enclosures-nozzles-.../filament-sensor-indicator/
I also used this one:
https://www.thingiverse.com/thing:3921921
For easier adjustment of the sensor and i also believe this mod allows a bit more adjustment room too.
RE: Erratic MMU2 - Time to uninstall?
I like that idea. To test it's working, I use Support, Sensors, and watch the 0 change to 1 when I insert the filament. I also set the menu to observe the sensors when the printer is being problematic during warm up. It seems to me that the sensors change when they should. Perhaps a hardware indicator would be better than a software indicator. I'll give it a shot. Thanks for the suggestion.
RE: Erratic MMU2 - Time to uninstall?
Sometimes, depending on the shape of the tip of the filament, the IR sensor may trigger incorrectly.
For example first trigger when tip first goes down since it usually is a little larger, then when tip is further down and have cleared the filament sensor, the sensor no longer senses the filament.
A LED helps, i used two SMD resistors and a blue SMD led, and then printed a new IR sensor cover with a small window printed in clear filament.
RE: Erratic MMU2 - Time to uninstall?
The Original description sounds very familiar. My Mk3S/mmu2s is so unreliable I use the mini for everything unless I absolutely have to run a second printer Or if the part is too big.
Your loading problems sound very much like mine. Almost random retracts of filament are common. More common is seeming random failures of any point in the load sequence. Sometimes various button presses might save the print. But once a random retract has happened it’s a fairly certain failure from there.
It seems that once a fail of any sort happens it gets lost as to where it is up to and Even if I seem to fix that problem it then it starts But frequently progress doing the bizarre failures, retracts or retracts the filament and it then won’t advance it again.
Turning it off and on again seems to be the only way to advance past the confusion it has. But can’t just turn it off . Usually have to follow a sequence.
Turn off the current print seizure with the panic button, then poke a tool in the reset button in the MMU then push middle button. Then turn the whole machine off at the power switch. Remove filament entirely from the machine to be sure it’s not still activating anything. Wait a minute then turn it back on. Every step has to be done with significant pause between them to allow lights to blink and cycle. Go too fast and it seems to get overloaded or confused as to where it’s at.
Most of the time this sequence sets it going right again. Miss any of the steps or go in wrong order or too fast and it locks up again.
I’m seriously at the point of pulling it off and going back to plain Mk3S. I’ve given up trying to print multicoloured stuff anyway. Almost all my work is single colour anyway. It’s not worth the trouble for the occasional colour print.
RE: Erratic MMU2 - Time to uninstall?
Sometimes, depending on the shape of the tip of the filament, the IR sensor may trigger incorrectly.
For example first trigger when tip first goes down since it usually is a little larger, then when tip is further down and have cleared the filament sensor, the sensor no longer senses the filament.A LED helps, i used two SMD resistors and a blue SMD led, and then printed a new IR sensor cover with a small window printed in clear filament.
You did what?! Can you post a couple pics of that?
If at first you don't succeed, redefine success!
RE: Erratic MMU2 - Time to uninstall?
It was not me that came up with the idea, found it on this forum, see links below.
https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-user-mods-octoprint-enclosures-nozzles-.../filament-sensor-indicator/
and
https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2
After adding the led i reprinted the cover but with a small square with clear filament over the led so it can shine thru the cover.
RE: Erratic MMU2 - Time to uninstall?
@torbjorn-j3
This is brilliant! I really think the proper calibration of the IR sensor is 90 percent of the feed issue problems out there for the MMU2S. A simple LED would make that readily apparent in a way that the software solution doesn't. I am definitely looking into building this!
RE: Erratic MMU2 - Time to uninstall?
It was not me that came up with the idea, found it on this forum, see links below.
https://forum.prusa3d.com/forum/original-prusa-i3-mmu2s-mmu2-user-mods-octoprint-enclosures-nozzles-.../filament-sensor-indicator/
and
https://bunnyscience.dozuki.com/Guide/Bunny+and+Bear+(BNBSX)+MKS3+Geared+Extruder+Assembly/2After adding the led i reprinted the cover but with a small square with clear filament over the led so it can shine thru the cover.
Ha! That is quite clever. Ive never felt the need for anything more then the LCD menu sensor display, but yea thats still a pretty good idea.
If at first you don't succeed, redefine success!
RE: Erratic MMU2 - Time to uninstall?
@benr
Well, problem is the lcd menu to check sensor is not always available when you have problems, so you may not be able to see it when you need to. plus a led will react immediately and not go thru the processor that may or may not be busy with other stuff.