MMU2 Homing Issue
Hello!
I have the MMU2 for more then a month and it has been doing good, now recently I have ran into an intermittent issue which I believe is an issue.
Upon turning on the printer and the MMU2 attempts to home but the steppers struggle to home, especially evident on the Finda-Selector assembly. I have even removed the selector motor and powered on the unit to see what happens with the motor and it seems to false flag "hitting the wall" for homing.
I have tried reinstalling firmware on both mmu2 and the mk3 and also tried the older firmware of the mmu2 and the issue still occurs. My only guess it would be the MMU2 controller or possibly the PSU but the printer still seems to print perfectly without the MMU2 so unlikely.
I am stuck at what I could do to troubleshoot more especially since it only happens about 50% of the time.
I have a video of it:
at the timestamp 1:15 you can see me starting the printer without the motor installed and it still has issues.
The motor has been replaced and both motors have the intermittent issue so it cannot be that.
So really I think I'm left two things, either the einsy board or the mmu2 control board is damaged, any thoughts?
Any help or suggestions would be greatly appreciated!
Re: MMU2 Homing Issue
i decided to test mine and it is doing similar things that it didn't do when i first got it.
i did test the movement after it loaded F1-F5 and it selected correctly.
mine is acting weird also after the machine has been turned off a few hours
ok i double checked my connectors on the MMU2 in the back and nothing was loose at all... now the longer the machine is on and i cycle the power it is going back to how it was when i first turned it on when new
Just curious; if you put the MMU2 back together leave the machine turned on doing nothing for like 5 minutes. then cycle the power and see if the start of the MMU changes back to normal.
“One does not simply use a picture as signature on Prusa forumsâ€
Re: MMU2 Homing Issue
ok so my machine when it was turned off for the entire day definitely acted strange on start up. it was chugging/skipping and the selector did not go to center it went all the way left and hit the wall.
now the machine has been on a little while and i cycled the power and it acts normal. you can see a difference between the two videos shot about 10 minutes apart.
so something is not 100% in the MMU2. it is acting like a capacitor isn't charging or the components are acting different until they warm up.
“One does not simply use a picture as signature on Prusa forumsâ€
Re: MMU2 Homing Issue
ok defiantly an issue here
here is my machine left turned off for about an hour
this is the very first switch on.
I've now left the machine turned on and will take another video a few minutes later.
“One does not simply use a picture as signature on Prusa forumsâ€
Re: MMU2 Homing Issue
ok big difference a few minutes later
“One does not simply use a picture as signature on Prusa forumsâ€
Re: MMU2 Homing Issue
so something is not 100% in the MMU2. it is acting like a capacitor isn't charging or the components are acting different until they warm up.
I think it could possibly be the heat, right now the room temp has been cool around here (70F | 21C) and I have been experiencing less issues then when the room temp was at around 80F (27C)
Re: MMU2 Homing Issue
so far my machine is doing random stuff on cold start up but occasionally when i reset when warm it also sometimes acts strange on startup. however during actual printing it seems to be ok.
“One does not simply use a picture as signature on Prusa forumsâ€
Re: MMU2 Homing Issue
My MMU2 also behaves randomly on start up. Sometimes it homes at the filament 1 position, then pauses for 20 seconds or so, then homes back to the right, then moves to the centre, then homes back to filament 1 again which I believe is the way it is supposed to function as that is described in the filament length calibration instructions.
But other times on power on it crashes into the filament 1 end and grinds for a few seconds, then simply stops at that. Or even sometimes repeats that but never moves to the right end or the middle position.
Why is the startup of the MMU so random? It makes me uncomfortable not knowing exactly what it is doing.
Re: MMU2 Homing Issue
I am 100% with you - the machine is, and has been since I got it, unreliable. Sometimes the motors move, sometimes they do not. Sometimes it loses home, sometimes it does not.
I can print the same g-code on the same machine back to back and get different behaviors. It's super hard to debug when the same code won't do the same thing twice in a row.
I often feel it is better with Rob's code. I'm not sure. It sure seems like something heats up because resets and timing matter, though I can't piece together how.
Perhaps watching the MMU PCB with an IR camera would help. Similarly, logging voltages in a few spots might be helpful. to be honest, the mk3 itself sometimes boots up fast, sorts files fast, menus are responsive. Sometimes, you turn it on, and it's a huge slow lumbering mess with SECONDS to respond to input.
I feel the serial communications are poor - either in the coding, or in the wiring, but when it's noisy, the printer spends all day trying to resend and re-ack stuff. When its quiet it prints nicely.
It's WELL WORTH of discussion but try to bring it up and watch the whole of the PRUSA community come to your door with pitchforks.
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edit: Another thing: If the filament isn't pre-loaded all the way, I feel i interferes with the homing process, or where the drum comes to rest after homing such that homing is lost. This is due to extra force on the drum from the fat end of the filament under the idler bearing(s), if I were a betting man.
I maintain an informal list of San Diego, CA 3D printing enthusiasts. PM me for details. If you include a contact email and I can add you to the informal mailing list.
RE: MMU2 Homing Issue
Hello! I experience exactly the same symptoms that are described in this thread. I'm puzzled about the fact that it seems that nowhere a real explanation and solution is described. I would be grateful for a hint that can help to find a solution. Everything else on my MK3s / MMU2s works super. The only recurring problem is this strange random behavior of the homing function for the selector.
RE: MMU2 Homing Issue
I have this issue as well. It is something that has gotten worse with time to the point that to print now I am reduced to single color, waiting for the printer to detect MMU failure then force the filament to the print head and reset the MMU.