Is the MMU2 "ready" and worth it?  

Page 4 / 6
  RSS
cwbullet
(@cwbullet)
Illustrious Member
Posted by: @ssill2

I will also add that the prusa could do better here with communicating with it's users.   There are numerous outstanding issues against the mmu firmware project on github yet it hasn't be committed to in 2 years.  Causing some to ask if it's abandoned.

They have been in business for years.  I doubt it is gonna happen.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 07/05/2021 10:06 pm
ssill2
(@ssill2)
Prominent Member

@cwbullet

I was trying to give you a solid reasoning behind my opinion 🙂  I just watched the most recent prusa live,  they did mention a complete refactor of the mmu firmware.  That's code for it's going to be a while 🙂  I write software for a living so I get the complexity involved, especially for something written in C/C++.  And that's fine, but realistically for most folks that have had a good experience with the base printer, they're going to be fairly disappointed in the MMU experience.

Posted : 07/05/2021 10:15 pm
Baklin
(@baklin)
Reputable Member
Posted by: @wfvn
 
The movement of the 'arm' in and out the IR-sensor is way too little. An arm which is twice as long should solve the problem with ease. But a chimney twice as high as it is now doesn't seem a good idea to me so another solution is needed. I'm still thinking about it.

This was posted today on PrusaPrinters.

https://www.prusaprinters.org/prints/66215-tzb-mk3smk25smmu2s-extruder-mmu2s-no-tower-v3

 

He doesn't give much info there, but looking at the files it looks like it uses an higher ratio for the movement of the sensor arm. And there is a hole in the bondtech door to add a grub screw for adjustment.

 

This is the only picture I could fine quickly that shows the parts installed.(this is an older version he made)

Posted : 08/05/2021 7:15 pm
ssill2
(@ssill2)
Prominent Member

@baklin

Wow nice.   might be worth a shot.

Posted : 08/05/2021 7:24 pm
wfvn
 wfvn
(@wfvn)
Eminent Member

I agree with ssill2. That looks promising. Personally I'm not really fond of multiple pivots/levers but in this case the magnets should make my 'objections' less important. I'm giving it a try.

There is one thing I think might be a good addition: a small bolt where the head of the rod is to ajust the position of the rod (bolt pushing rod further in or not).

But I'll try the V3 as it is right now. Waiting for the current print to end, then I'll print the parts. Gcode loaded into the MK3_ already.

------------------------

Another thing. After last print I mentioned (3 color Flex print), I got more issues with resistance in the tubing from filament spool to the nozzle. Filament got stuck many times after a while resulting in a 'cut off ' print at a certain height. The tubing between filament spool and buffer is 4x3mm so room to spare for the filament inside that tube. I want to make the entire route from filament spool to nozzle way shorter. Also I'm planning on using the Ikea Lack thing for housing (so printing PC Blend a little easier). But I want the MMU2S outside of the housing in order to have excellent access to the MMU2s.

I think placing the FIlament spools on top of the Lack 'roof' but not on the front side but the back. The filament spools should 'give filament' on the top side' of the spool to make the distance between spool holder and filament buffer as short as possible. The MMU2s on the top also but on the front part. Instead of facing 45 degrees up I want it to face 45 degrees down. A small hole or slot for the tubing between extruder and MMU2s selector. Between MMU2s and spool holders there should be just enough room to put a filament buffer. But also the Filament buffer should be with as less friction as possible but also very easy to load.

...
Posted : 09/05/2021 12:44 am
ssill2
(@ssill2)
Prominent Member

@wfvn

Great,  let us know how it goes!  Anything to improve the reliability of the mmu.

Posted : 09/05/2021 12:49 am
Baklin
(@baklin)
Reputable Member
Posted by: @wfvn

 

There is one thing I think might be a good addition: a small bolt where the head of the rod is to ajust the position of the rod (bolt pushing rod further in or not).

 

The v3 has a hole in the bondtech door for that bolt already. The are some pictures with that adjusting bolt in the v2 comments

 

Posted : 09/05/2021 1:23 am
wfvn
 wfvn
(@wfvn)
Eminent Member

@baklin

I Just took the printer parts from my printer and noticed the hole. Nice work it is. I need to print the T shaped rod again, this one failed. This afternoon I will assemble the extruder. Can't wait to try it. Looks excellent.

 

...
Posted : 09/05/2021 3:06 pm
ssill2
(@ssill2)
Prominent Member

Last night I was trying to print something for like the third time and it got to where all the orange lights were blinking, even though nothing was in the filament path.  I determined that the angle the MMU2 is sitting at allows the filament sensor bearing to get close enough to the finda, even with magnet enabled selector to trigger.  unclipping the mmu from the printer frame so the angle was reduce made the lights turn green again.  I think I'm going to print the following and see if that helps at all

 

https://www.prusaprinters.org/prints/20114-mmu2s-horizontal-mount/files

 

Posted : 09/05/2021 3:12 pm
ssill2
(@ssill2)
Prominent Member

So I did print and install the horizontal mounting brackets for the MMU.  Just kicked off another attempt at the huey rotor blade in .1mm layer height Paramount 3D PETG.  I printed the fueselage with the exact same settings and filament just fine.  I began to suspect that the bvoh had taken on moisture over the course of a two day print.  I know how a filament dryer going that dries it during print.  I'll see how this goes.

Posted : 09/05/2021 8:07 pm
ssill2
(@ssill2)
Prominent Member

Posted : 09/05/2021 8:08 pm
wfvn
 wfvn
(@wfvn)
Eminent Member

Printed the extruder without the chimney. I assembled it and put it on my printer.

 

First few loads were a success. First unload wasn't. The hatch didn't fall back in place. I used a 3.5mm drill bit to widen the hole for the Bolt with nut. Success.

 

Now try some printer jobs and find out hoe of will hold

 

...
Posted : 09/05/2021 9:32 pm
cwbullet
(@cwbullet)
Illustrious Member

After reading many threads and building one MMU2, I think it is not worth it.  I built one and sold it.  I think I am gonna wait for the MMU3 or go with palette.  

--------------------
Chuck H
3D Printer Review Blog...
Posted : 09/05/2021 11:58 pm
ssill2
(@ssill2)
Prominent Member

@cwbullet

I have to say, so far, this horizontal mount seems better.  But that could change today, tomorrow, or whenever this temperamental best decides to lol

I'm hoping to hear experiences of people with the palette,  it might sway me.  At this point I feel like the only real solution is something like an E3D tool changer.  As I understand you don't have to have a purge tower and thus aren't blowing a bunch of filament, particularly with solubles because you have to purge so much out.

Any reasonably sized MMU print wastes so much filament and that purge block takes up room on your build plate.

This post was modified 1 month ago by ssill2
Posted : 10/05/2021 12:07 am
ssill2
(@ssill2)
Prominent Member

Ok so the print failed, but not because of anything mechanical this time. The soluble material on the purge tower simply won't bridge, and makes a huge mess.  I've seen this before but never this bad.   I think the fact that it's trying to bridge .1mm layers of soluble filament across 6mm in the purge tower is causing all kinds of issues with adhesion.

See pics.  I'm just about out of BVOH but I have a spool coming today or tomorrow so I'm going to set the max bridging distance on the purge tower to 0mm and try this print again.  I think the horizontal mount of the MMU helps a lot to prevent the ball bearing near the finda from falsely triggering.

Posted : 10/05/2021 12:32 pm
ssill2
(@ssill2)
Prominent Member

So for anyone who is having problems with the above issue or similar.  I found a decent work around.

It was suggested by someone here:

https://github.com/prusa3d/PrusaSlicer/issues/1948

And it seems to work!

I've had a print going overnight and here's what the purge block works with a big x shaped object in the middle of it.  C0mpare it to the one above

Prusa definitely needs to make the use of the purge block smarter when using solubles.  I've had the messy purge block happen with both PVA and BVOH.  I probably won't get anymore PVA after I use up my spool of primaselect since bvoh as stated by prusa works for both PLA and PETG.   Just thought this might be useful.

Posted : 11/05/2021 12:23 pm
ssill2
(@ssill2)
Prominent Member

ok,

The Saga of this damn huey is almost complete.  Main rotor is printed!

Just started the tail rotor.

Then I'm never ever printing this thing again lol

 

Posted : 12/05/2021 1:57 pm
Baklin
(@baklin)
Reputable Member

I like the tip about the cross in the purge block. That could be helpful some day.

Posted : 12/05/2021 3:03 pm
ssill2
(@ssill2)
Prominent Member

It does the trick!   Before this, PVA and BVOH exactly the same thing.  I had to get the vacuum cleaner out because the soluble flaked off the purge block.  Kudos to the person mentioned this on the github PrusaSlicer issue.

Posted : 12/05/2021 3:09 pm
ssill2
(@ssill2)
Prominent Member

And it's done!

Posted : 12/05/2021 4:00 pm
Page 4 / 6
Share:

Please Login or Register