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Is the buffer really necessary?  

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Gilly Barr
(@gilly-barr)
Active Member
Is the buffer really necessary?

I recently built the MMU2 and have done a few small prints with it.

I'm really frustrated that the buffer takes so much space on my table behind the printer, and causes the spools to be farther from the printer, and I'm trying to find better solutions.

I would like to hang filament holders on the wall behind the printer, but the buffer still takes too much space in my opinion.
I've seen some custom 'buffers' that are slightly smaller, but I'm wondering if the buffer is even necessary.
There are images of MMU users I've seen that don't have the buffer at all, so I'm looking for more opinions regarding the buffer being necessary at all...?

 

Thanks in advance!
Gilly.

Posted : 13/01/2021 9:27 am
Gilly Barr
(@gilly-barr)
Active Member
Topic starter answered:
RE: Is the buffer really necessary?

For example - I've seen this person using the MMU2 without a buffer, and claims to work pretty good. Wondering how common this is.. 

https://www.prusaprinters.org/prints/24121-prusa-i3mk3-mmu2-teflon-tube-inlet-wall-mount/comments

Posted : 13/01/2021 1:12 pm
JoanTabb
(@joantabb)
Moderator
RE: Is the buffer really necessary?

@gilly-barr

I don't have actual buffers on either my MMU1 or MMU2

I have my filament spools on a shelf above the printer, and I hade drilled a 4mm hole through the shelf inside the back of each spool holder, 
I feed a 100mm length of PTFE through this hole, and it is tight enough to retain the PTFE

I put the filament spool on the dispenser and feed the filament through the PTFE so it comes out under the shelf. 

then I adjust the PTFE feed tube on My MMU, to be long enough to gently curve up to meet the tube through the shelf....    then I load the filament as usual,,,  

what happenns, is that whilst the extruder is using filament, the end of the filament feed tube buts against the end of the short PTFE tube, and the filament is pulled off the spool, through both PTFE tubes and into the MMU/Printer... 

when the MMU 'Parks the filament, it backfeeds the filament down the feed tube which results in a gap forming between the ends of the two PTFE tubes, where the filament forms a loop, instead of feeding back to the reel and causing the filament to fall off the edge of the spool

next time the filament is needed, the extruder pulls the filament along the feed tube, until the loop of filament is utilisedand the ptfe ends meet up, then any further filament is pulled off the reel...    
this is simple and cost effective

I also use 2.5mm ID Ptfe for all MMU2 tubes except the Extruder cold end liner to reduce friction, 
and I put larger rollers on the filament reel holders to reduce friction there too... 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 13/01/2021 1:34 pm
3DWillem
(@3dwillem)
Active Member
RE: Is the buffer really necessary?

@joantabb

Can you post a photo from your setup?

Posted : 13/01/2021 2:33 pm
Thejiral
(@thejiral)
Trusted Member
RE: Is the buffer really necessary?

I use the universal rewind spool ( https://www.thingiverse.com/thing:3338467; with the stiff spring printed in Prusament PETG, only the spool rewind spindle, the holding frame is a custom design which is more compact than the official one)  which only needs a a few cm extra width per spool but otherwise no extra space at all. I have to admit that it took me a bit until I dialed it in but since I did it works very reliably.

The buffer/rewind or something entirely different solution is a matter of taste to some extend I believe.  There are so many solutions out there.

This post was modified 10 months ago 2 times by Thejiral
Posted : 13/01/2021 2:38 pm
JoanTabb
(@joantabb)
Moderator
RE: Is the buffer really necessary?

@3dwillem

Sorry, due to covid precautions I am 70 miles from My MMU printers... 

However if you have a good imagination, this diagram might help


Regards Joan

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 13/01/2021 4:09 pm
Gilly Barr
(@gilly-barr)
Active Member
Topic starter answered:
RE: Is the buffer really necessary?

@joantabb

I think I understand what you mean. I want to do something similar, so I think i'll set it up like that without the buffer and see how it goes..

Thanks! 🙂

Posted : 13/01/2021 8:08 pm
Gilly Barr
(@gilly-barr)
Active Member
Topic starter answered:
RE: Is the buffer really necessary?

@thejiral

Seems like a good work-around, but I don't feel like spending so much time printing 5 spool holders like these, and then just having more 'mechanisms' to maintain.

I think i'll try first something much more simpler like @joantabb suggested.

Another idea I'm wondering if will work is if I design a small filament 'clip' that will allow the filament to be pulled in one direction. Then this will force the filament to create a 'loop' of some sort when being backed up to the spool...?

Posted : 13/01/2021 8:19 pm
jsw
 jsw
(@jsw)
Noble Member
RE: Is the buffer really necessary?

I've done it without the buffer, letting the filament coil loosely behind the machine.  Of course I do watch it closely.  The buffer is a more clean solution.

Posted : 13/01/2021 10:46 pm
mikeessayhub
(@mikeessayhub)
New Member
RE: Is the buffer really necessary?

The MMU is great, but big source of frustration, it just fails too much. Please make next version that is more reliable.

 

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Posted : 15/01/2021 4:54 am
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Thejiral
(@thejiral)
Trusted Member
RE: Is the buffer really necessary?

@mikeessayhub

It really is a matter of having it dialed in well though. When you have figured everything out, the MMU can be pretty reliable. The problem is, that it is definitely not unbox it and print, like the MK3s is. Some encounter few if any teething problems, others more but if you have the stamina to work through it, you get a very nice system that works just fine. Only the palette can do something similar, at a much steeper price and not without issues either, as far as I have heard. That said, the MMU is of course slow and extremely wasteful, especially when you go down to very low layer heights (0.1 mm) as I have done recently.

 

@gilly-barr

I understand you completely. Those rewind spools are yet another complexity added to the system which need to be dialed in or at least figured out. They are probably the cleanest solution however. As I have my printer enclosure in the living room, I wanted to have a clean solution to it all.

To be honest, I have never even tried it with the buffer, so I can't even compare really.

 

Posted : 15/01/2021 2:30 pm
Gilly Barr
(@gilly-barr)
Active Member
Topic starter answered:
RE: Is the buffer really necessary?

@thejiral

Thanks a lot for the reply!
The MMU definitely requires some work, but the end results I think are more than worth it! 🙂

Posted : 16/01/2021 12:14 pm
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