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Bowden Length Part Problems  

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brian.m6
(@brian-m6)
Active Member
Bowden Length Part Problems

Hi,

Been a while but I got back to my MMU2 unit and was trying to calibrate the bowden lengths. The first three went pretty well although the third one I have no confidence it will work during printing as it took many times to calibrate the length and it kept undershooting or overshooting before that.

However my question is about the fourth one that I cannot get working. After looking at it, it appears that the filament will not load correctly because the part that came with my kit was not aligned correctly. Basically the filament will make it to the gears and will attempt to load but the filament will not go beyond the gears because the friction is too high. Manually I can push it through when I start the loading process but on its own it will not work. I pulled it all apart and tried putting some filament through after the gears and I can feel the resistance. The filament is not being chewed up by the gear as it almost immediately stops attempting the load so that is good. I can also push filament back through from where the orange tubing leading to the extruder is and there is no resistance....

So how do I fix this?

 

Posted : 02/09/2019 2:32 pm
Peter L
(@peter-l)
Honorable Member
RE: Bowden Length Part Problems

Is this MMU2 or MMU2S?

The MMU2S doesn't require calibrating the bowden length because it uses the sensor on the extruder instead. It's also much more reliable.

If you're still on the older MMU2, you should probably upgrade to the MMU2S.

Posted : 02/09/2019 8:28 pm
brian.m6
(@brian-m6)
Active Member
Topic starter answered:
RE: Bowden Length Part Problems

Well I ordered the upgrade kit but it did not have any printed parts though I thought I ordered the printed version. So I cannot do any upgrades to the MMU2S until I get the MMU2 printing something at least. Right now I cannot get past the bowden calibration to do that. Also this is not a calibration problem exactly. The main part is having issues with alignment or something of that nature so that when the gears try to feed to filament through the assembly above, it has too much friction and then simply unloads it. So even if I upgrade something that makes calibration not required, if the filament is not going to feed then it still will be an issue.

Posted : 02/09/2019 11:06 pm
brian.m6
(@brian-m6)
Active Member
Topic starter answered:
RE: Bowden Length Part Problems

Hmm... is it still possible to somehow get the printed parts for the MMU2 to MMU2S upgrade somewhere? I love the idea of the MMU2 but right now I am considering just throwing it out the window and going back to single filament printing. Love the idea of water soluble supports for miniatures I print for gaming but right now it is the worst money I have spent and I just want to get back to printing... 

Posted : 03/09/2019 4:06 pm
gnat
 gnat
(@gnat)
Noble Member
RE: Bowden Length Part Problems

There are no physical changes for the MMU. The printed parts are for the extruder (S upgrade if you have a plain MK3 or just the IR tower if you already had an S) and buffer.

MMU tips and troubleshooting
Posted : 05/09/2019 4:59 pm
brian.m6
(@brian-m6)
Active Member
Topic starter answered:
RE: Bowden Length Part Problems

I got that already where the printed parts go. I thought the MMU2 already updated everything to the MK3S extruder... I know I updated it with printed parts in the MMU2 kit that I received. Still I cannot print the upgraded parts for the extruder either because my printer hates me since I updated to the MMU2... So I am trying to get it working but everyone says upgrade to the MMU2S but how can you do that when your printer is not functioning... I cannot print extruder parts either unless I just remove the MMU2 completely and if I do I am not sure I would even put it back on.

Posted : 06/09/2019 2:36 pm
gnat
 gnat
(@gnat)
Noble Member
RE: Bowden Length Part Problems

You can't simply print parts to upgrade to the 3S as the filament sensor is different. Prusa should have sent you the MK3S/MMU2S kit so you shouldn't have to buy or print anything. If you did not get that kit from them, I would suggest contacting support and find out why you didn't get it.

MMU tips and troubleshooting
Posted : 06/09/2019 3:24 pm
brian.m6
(@brian-m6)
Active Member
Topic starter answered:
RE: Bowden Length Part Problems

So to clarify... I do have the new filament sensor. I mentioned earlier that I ordered the printed part kit but got the unprinted part kit so I have the updated sensors and other things. I just do not have the printed parts. I can ask again if I can order them.

I added a picture of where the friction is in the MMU2 but I have no idea how to solve it.

Attachment removed
Posted : 06/09/2019 3:36 pm
gnat
 gnat
(@gnat)
Noble Member
RE: Bowden Length Part Problems
Posted by: brian.m6

So to clarify... I do have the new filament sensor. I mentioned earlier that I ordered the printed part kit but got the unprinted part kit so I have the updated sensors and other things. I just do not have the printed parts. I can ask again if I can order them.

Ah. I misunderstood where it all stood.

So right now you currently have the MMU2 configuration with the MK3 extruder, is that correct?

You can simply disconnect the the MMU both from the extruder and the Rambo (either the power or comms will do) and then you can print normally as the base printer.

I added a picture of where the friction is in the MMU2 but I have no idea how to solve it.

Attachment removed

Apologies again for getting side tracked and missing the issue itself.

I believe there is a mod of that part running around somewhere as others have had difficulty as well. It's hard to tell from that picture due to the angle, but it looks like the gear may be shifted a tad to the right (pic orientation) which could account for the friction as it would be trying to raise the filament. You want to make sure that the gears are positioned so that the filament rides as close to dead center in them as possible. Any deviation will shift the filament path and cause issues.

The other option is to pull the shaft and gears completely and test the path. It could be that you have a print defect that is not aligning things properly or is more restrictive than it should be. If you have appropriate tools you might be able to fix it with some small files if that is the case.

MMU tips and troubleshooting
Posted : 06/09/2019 3:59 pm
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