Posting Out of pure frustration.
Just got this thing put together, I've always bragged up my mk3, but this mmu2s is... more than useless. The assembly was a little less detailed in spots than the initial mk3 build was, but no biggy. But the actual Operation of this is just pure SHIT. After trying an unload process is tried the damn switcher likes to i dont know go to home? well the problem is IT DIDNT UNLOAD so it drags the filament out of the thing then backs back over it. I've taken this thing apart more times than I can count.
I'm about positive the little cutter isnt working the way it's intended because well... it doesnt do little cutty things. I tried to adjust it down further, but then it gets snagged and ripped out of its holder. I guess I'm going to attemp to just get my newly assembled hot end printing tommorrow and see if that is even working, I have a feeling it's clogged somehow, even tho it was working flawlessly last time I used the machine. between the unloading and heating and reheating I assume something has gone awry.
Another thing does the IR sensor not communicate with the MMU? it clearly still has filament in the tube, why does the MMU think its ok to cycle? I've also had it try to print without any filament twice. Some how it made it that far. I'm tired of this and seriously upset that either prusa released an absolute shitbox of a product, the directions arent good/clear enough, Or I've just discovered I'm an absolute idiot.
Any suggestions besides "quit your crying" would be much appreciated.
RE: Posting Out of pure frustration.
I understanding your frustration. I did my upgrade last weekend and 2 days ago I was so frustrated I decided to put everything apart and put the MMU2s aside for a while and use the printer as a regular MK3s. While putting it apart, wouldn't you know, the extruder gear just fell into my hand... they warn to not overtighten it because it might strip the screw, but they only provide an Allen key whereas the screw is a torx 6 (thanks to someone's comment in the instructions). Anyway, put it back together and it works now. Just saying that when you get to this point of frustration, either remove the MMU2s and use it as a regular MK3s for now, or don't touch it for a couple of weeks and try again with a cooler head. 😉
RE: Posting Out of pure frustration.
Removing the MMU and getting the base printer working again is an excellent first step. One of the most common problems is that the IR sensor is not functioning correctly and if it provides bad results, then your life will be miserable. Find a good test print (30-60 minute run time) and keep working on it until you can get through an entire print without any false run-out issues.
Assuming you do find you have IR problems (like most of us) the first step is to look up the IR calibration process in the handbook that came with the MMU. If that doesn't fix it you need to look to the idler door.
The IR sensor works different with the MMU tower than it does with the plain MK3S and it's important to understand it to troubleshoot it well.
For the normal system the filament moves a ball which moves an arm that trips the sensor. This happens before the filament touches the gears. For the tower the IR flag is at the end of the arm on the idler door and it is moved when filament enters the gears.
There are two common issues with this system. The first is that the door does not move enough so the sensor doesn't get tripped fully. This can either simply be that you need to loosen the idler tension bolt or it could be that the door itself is too tight and doesn't move freely. With my MK3 I could easily manually feed filament to the nozzle with the steppers disabled, but the first thing I noticed after the S upgrade was that I could no longer do that. I had to print a new door and that fixed my IR issues and I can manually feed filament again.
The second issue is that the flag on your arm may simply not be big enough to trip the sensor correctly. There is a modified door on Thingverse (on my phone, sorry) with an bigger flag so you can sculpt it to fit with sandpaper or a file.
It is possible that you have both issues going on.
The reason I suggested above that you want to get through a reasonable test with no issues is that we have seen many cases where everything checks out while it is sitting still, but once things start moving the sensor will jitter because the flag is just barely tripping it and the movements cause it to wiggle just enough to untrip it.
After getting the IR sensor working the next most common issue with the MMU is friction. Make sure that the filament paths are as smooth and straight as possible. Drag will lead directly to change failures (because the filament doesn't move as expected/desired) and indirectly to failures by promoting tails to form due to extractions not happening at the proper speed.
Additionally, based on you description it sounds like you might want to double check the FINDA adjustment as it sounds like it might not be recognizing the filament is there properly. It is hard to see, but the FINDA has a light on it like the PINDA. It is lit when there is no filament and unlit when present. Play with adjusting it's height until you get consistently correct results when you feed filament through the MMU.
RE: Posting Out of pure frustration.
Assuming you do find you have IR problems (like most of us) the first step is to look up the IR calibration process in the handbook that came with the MMU. If that doesn't fix it you need to look to the idler door.
I am most impressed with the instruction guides from PRUSA but once in a while, I scratch my head when trying to figure out what they ask users to do. The IR calibration process in their handbook and assembly guide is one of those. There has to be a much better way to calibrate the IR sensor then moving the cover a bit to the right, a bit to the left, a bit more, then a bit to the right (paraphrasing). Maybe adding a couple of small notches in the plastic designs so that the cover always sit where it's supposed to would be a better approach?
RE: Posting Out of pure frustration.
Just in case jacob will come back or someone is struggling with the same issues.
It's essential for MMU2 operation to verify each part is working correct. You might get lucky and it just works out of the box. But most likely something is just not right assembled or configured.
My advise would be to go step by step. First verify the IR sensor is working fine. Means loading/unloading works perfectly. During operation it's not changing states. Correct screw tension is set. The filament tip looks good (no PTFE tube assembly issues). Once you feel confident the extruder is perfectly fine, go to the next step: the MMU unit.
On the MMU unit most underestimated parameters are the FINDA position and the screw tension. The filament need to trigger FINDA as it comes in but not with the first hair. The screws shouldn't squish the filament but bite hard enough to push the filament through small resistance obstacles which might occur. Once your confident with this setup, the next step is to make sure the filament buffer/feed is working fine.
Filament buffer, feeder or whatever system you're using should provide the filament without big resistance and take it back without get stuck. This is the easiest part to test but as essential as all the other.
There are tons other issues you might have or not have. But this items people do usually disregard. Because all bolts and wires are in place like in the manual doesn't mean the machine is calibrated. I can only encourage to go step by step and learn how this printer works or suppose to work. This will help to learn print difficult materials/objects and do really fun stuff with the printer.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Posting Out of pure frustration.
Thank you sir, I'm doing some non 3d projects for a week, but will for sure look at your post when i sit down and play with the printer again.
RE: Posting Out of pure frustration.
OK so... the damn knife wont cut, keeps getting ripped out of its holder... I guess I'm going to try printing that double sided one? I dunno. So thats one problem.
The other problem is I keep getting the "mmu requires attention" when there is nothing wrong up there I can tell? It loads and prints the first layer calibration just fine. It's so frustrating!
I took your guys' advice, did the IR calibration, seemed to go perfectly. I did find an issue first thing tonight, my short ptfe tubes on the MMU were backwards, the directions should really be more clear on that part, while assembling... hell even after assembly, I have no idea what direction is "facing out of the mmu" ? is that the direction of loading? or the direction towards the extruder? but got that fixed anyways.
SOOOOOO any other suggestions?
RE: Posting Out of pure frustration.
Update, something ... I dont know is just not working right. It keeps trying to switch filaments, and jamming up even if I Select single MMU print in slicer. I updated the software, just to make sure... nothing changed. I just want my printer back. Do i just select MK3s and bypass the mmu with my chosen filament? I am not happy with PRUSA at all right now.
RE: Posting Out of pure frustration.
If you want to print as a plain MK3S, you need to unplug the MMU from the Rambo (power and/or comms). Then you can insert filament directly to the extruder and print that way.
RE: Posting Out of pure frustration.
Printing now as mk3s, had a quick lil problem because I loaded some translucent red, so filament sensor wasnt working. but ya... other than that, doing good, at least now I can try to download that double knife holder, and some things I needed to do for some projects.
If anyone has any other ideas let me know.
RE: Posting Out of pure frustration.
Are you sure you have MK3s and MMU2s? Because on the "s" machine the sensor is infra red gate and by design doesn't matter which color you feed in.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Posting Out of pure frustration.
Yes. It took forever to get here because the upgraded everyone in line waiting for the mmu2 to the s and the mk3 to the mk3s if I remember correctly... also my parts bag I'm looking at says mmu2s... and I had to rebuild my extruder from the ground up and got a new style chimney and a fancy angled fan (not mk3s exclusive i know)
the box says 2s on it... hopefully I'm right about the 3s thing too? but its printing fine as a 3s just not when i throw the mmu into the equation.
RE: Posting Out of pure frustration.
Can you post a picture of your extruder?
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Posting Out of pure frustration.
This work?
RE: Posting Out of pure frustration.
That is indeed an S which means that the failure was coincidental to your filament. This is indicative of your IR sensor having issues as previously described.
Get your IR sensor sorted and that will help with a whole raft of issues with the MMU.
RE: Posting Out of pure frustration.
I can see the cap of the IR sensor sits not flush on the IR case. Please try to move the IR sensor by moving the IR cable up/down/back/forth and check if it's changing states.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Posting Out of pure frustration.
I don't know what else to do, it passes the handbooks lil Allen wrench test. I'm not feeding the filament through a ptfe time at the moment, would that make it have a problem? Excess light getting in or something?
RE: Posting Out of pure frustration.
Nikolai i thought that was odd too when assembled it! The pins stuck out too far on the little circuit board for it to close properly
RE: Posting Out of pure frustration.
During my upgrade I had to make it fit. I also had to modify the lever in order to achieve nice transition. Make sure the IR sensor sits tight and not wiggling/jumping around. Then make sure the lever is triggering it correct. By correct means the trigger should start after ~0.5mm movement and should return back ALWAYS.
I'm pushing against the screw (the one with the spring) to check on the trigger. It's a lot more accurate and you can feel/see when exactly it starts to trigger and if the door always comes back without any resistance.
Often linked posts:
Going small with MMU2
Real Multi Material
My prints on Instagram
RE: Posting Out of pure frustration.
I don't know what else to do, it passes the handbooks lil Allen wrench test. I'm not feeding the filament through a ptfe time at the moment, would that make it have a problem? Excess light getting in or something?
No, light is not an issue here. Without the PTFE is fine and arguably better for debugging IR issues as more movement of the filament is possible.
Issues here all come down to the flag not properly breaking the beam. This is due to:
- Bad tower positioning (sounds possible here)
- The door not moving correctly (tension too tight or bad door)
- Or the flag not doing its job
While one of the first two is the likely real cause for the 3rd, printing the modded door with the larger flag will let you sculpt to work more reliably even if the others aren't perfect (e.g. adds some slop coverage).