Is the buffer really necessary?  

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

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... 

RE: Is the buffer really necessary?

@joantabb

Can you post a photo from your setup?

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.

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

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! 🙂

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...?

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.

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.

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.

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! 🙂

RE: Is the buffer really necessary?

Joan,

I know this is an older thread but, I am currently in the final stages of setting up my MMU3, and I hate the buffer that Prusa offers. I am using the spool holders that came with the MMU3, and they seem to work well enough. I really like the simplicity, and presumable ease of swapping filaments that your set up seems to offer. My main question is, how much does the MMU actually backfeed? How much allowance do I actually need to give?

Thanks. Brad.

Posted by: @joantabb

@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... 

 

Posted by: @joantabb

@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

RE: Is the buffer really necessary?

I still have an aversion to buffers... 

As you can see in the post above. 

However if you have particularly sensitive filaments, PVA and Nylon for example free air buffering may not be the best option!

regards Joan

I don't print nylon or PVA...

RE: Is the buffer really necessary?

Posted by: @joantabb

I still have an aversion to buffers... 

As you can see in the post above. 

However if you have particularly sensitive filaments, PVA and Nylon for example free air buffering may not be the best option!

regards Joan

I don't print nylon or PVA...

Joan,

My question is how much does the MMU actually backfeed? My plan is to affix the short spool feed tubes, but how much clearance real estate should I give the free end of the feed tubes that are directly connected to the MMU?

And, while I’m at it…. Does it only backfeed when it’s changing materials/colors?

I know I’ll figure all this out when I start printing, I just hate wasting rigging time when someone else has most likely already figured out the mistakes not to make.

Thanks. Brad.

RE: Is the buffer really necessary?

Posted by: @mmpllc

 

Posted by: @joantabb

I still have an aversion to buffers... 

As you can see in the post above. 

However if you have particularly sensitive filaments, PVA and Nylon for example free air buffering may not be the best option!

regards Joan

I don't print nylon or PVA...

Joan,

 

My question is how much does the MMU actually backfeed? My plan is to affix the short spool feed tubes, but how much clearance real estate should I give the free end of the feed tubes that are directly connected to the MMU?

 

And, while I’m at it…. Does it only backfeed when it’s changing materials/colors?

 

I know I’ll figure all this out when I start printing, I just hate wasting rigging time when someone else has most likely already figured out the mistakes not to make.

 

Thanks. Brad.

It back feeds when swapping colors in a print you need probably 10 cm clearance between each tube and it backfeeds about 40 cm fillament 

RE: Is the buffer really necessary?

OK…. So now I’m going to backpedal a little bit.

Now that I’ve figured out how the buffer actually works (I forgot the cartridges come out, and was trying to load the filament with my hands between the buffer plates), I actually think I like it.

So my question is…. Why don’t those who don’t like it don’t like it? As a rookie, what am I missing?

Thanks. Brad.

RE: Is the buffer really necessary?

Posted by: @mmpllc

OK…. So now I’m going to backpedal a little bit.

 

Now that I’ve figured out how the buffer actually works (I forgot the cartridges come out, and was trying to load the filament with my hands between the buffer plates), I actually think I like it.

 

So my question is…. Why don’t those who don’t like it don’t like it? As a rookie, what am I missing?

 

Thanks. Brad.

Ok first it loads in and out the same side so if you've got your spools behind the printer that's a problem second of all on long prints fillament can come out the top third it's really annoying to load I'm going to try this one out https://www.printables.com/model/3292-mmu2-filament-buffer diffrent people have diffrent setups mah I ask what your setups like maybe a photo

RE: Is the buffer really necessary?

Hello,

I have not noticed the filament retracting enough to escape the buffer. It seems Prusa has worked out sizing pretty well. My only initial contention with it was that it was such a PITA to load the filament to the MMU. But, as I said, I was going about it all wrong. I had forgotten that the cartridges came out, and was trying to load the filament with my hands wedged in between the buffer plates, where there was obviously not nearly enough room for. I began to wonder what it was going to be like to have to swap filaments on a regular basis, or reload after emptying spools. But now that I’ve figured out the obvious; that the cartridges come out for the “load to MMU” process, I haven’t had any issues with the buffer. My question is in regards to those who say they don’t like it at all, going on the relatively safe assumption these individuals have gotten beyond my contentions with it, and have issues beyond that 

Right now, I’m in the process of working out a better spool mounting setup, as the spool holders that are supplied with the MMU. They are…. Less than sufficient. And they are contributing to print issues and failures.

This is my current setup, aside from the fact that the spool holders are slated for the scrap pile.

Thanks. Brad.

RE: Is the buffer really necessary?

Posted by: @mmpllc

Hello,

 

I have not noticed the filament retracting enough to escape the buffer. It seems Prusa has worked out sizing pretty well. My only initial contention with it was that it was such a PITA to load the filament to the MMU. But, as I said, I was going about it all wrong. I had forgotten that the cartridges came out, and was trying to load the filament with my hands wedged in between the buffer plates, where there was obviously not nearly enough room for. I began to wonder what it was going to be like to have to swap filaments on a regular basis, or reload after emptying spools. But now that I’ve figured out the obvious; that the cartridges come out for the “load to MMU” process, I haven’t had any issues with the buffer. My question is in regards to those who say they don’t like it at all, going on the relatively safe assumption these individuals have gotten beyond my contentions with it, and have issues beyond that 

 

Right now, I’m in the process of working out a better spool mounting setup, as the spool holders that are supplied with the MMU. They are…. Less than sufficient. And they are contributing to print issues and failures.

 

This is my current setup, aside from the fact that the spool holders are slated for the scrap pile.

 

Thanks. Brad.

Whats wrong with the spool holders I like them