Filament buffer useful?  

RE: Filament buffer useful?

My take on your questions for my own MMU:

- Not me,

-A royal PITA, even if not attached to the wall and you need to reach over a table and around a printer.

- I'm running variations of the auto-rewind spool holders in my own dryboxes instead. I consider them a significant QOL improvement. 

https://www.prusaprinters.org/prints/22023-auto-rewind-sistema-5l-drybox/

RE: Filament buffer useful?

Once I got things sorted out, I have found the buffer to be perfectly functional.

1. You need the pass through festo mod: https://www.thingiverse.com/thing:3545935
   • I used the setup variant so that all 5 enter from the same side.
2. Similarly, use the festo mod for the MMU itself: https://www.thingiverse.com/thing:3233579
3. Get good quality PTFE tubing
   • I'm using CapricornXS, but I apparently got an amazing deal on it compared to it's usual price.
4. Make sure any curves that must be in the PTFE are as gentle as possible. The straighter the path, the better.
5. This is a helpful tool for loading the buffer: https://www.thingiverse.com/thing:3616370
6. I setup a 2020 frame to hang my spools above the printer. You can see the frame here: https://www.thingiverse.com/thing:3693562
   • I have since stopped using the auto-rewind spools shown (I gave them to @vintagepc actually 😆) and instead use a modified version (I cut off the rewind part): https://www.thingiverse.com/thing:3703800
7. Finally I made a replacement for part of the buffer that adds hooks for it to hang off the back of the 2020 frame: https://www.thingiverse.com/thing:3703814
   • I since added the festo mod and all PTFEs enter on the right side of the pic shown in that Thing.

Between the festo mod moving all the inputs to the same side (outputs too) as well as giving your fingers more room to work and the helper tool I can load all 5 filaments pretty quickly with little hassle.

RE: Filament buffer useful?

Posted by: @gnat

Once I got things sorted out, I have found the buffer to be perfectly functional.

1. You need the pass through festo mod: https://www.thingiverse.com/thing:3545935
   • I used the setup variant so that all 5 enter from the same side.
2. Similarly, use the festo mod for the MMU itself: https://www.thingiverse.com/thing:3233579
3. Get good quality PTFE tubing
   • I'm using CapricornXS, but I apparently got an amazing deal on it compared to it's usual price.
4. Make sure any curves that must be in the PTFE are as gentle as possible. The straighter the path, the better.
5. This is a helpful tool for loading the buffer: https://www.thingiverse.com/thing:3616370
6. I setup a 2020 frame to hang my spools above the printer. You can see the frame here: https://www.thingiverse.com/thing:3693562
   • I have since stopped using the auto-rewind spools shown (I gave them to @vintagepc actually 😆) and instead use a modified version (I cut off the rewind part): https://www.thingiverse.com/thing:3703800
7. Finally I made a replacement for part of the buffer that adds hooks for it to hang off the back of the 2020 frame: https://www.thingiverse.com/thing:3703814
   • I since added the festo mod and all PTFEs enter on the right side of the pic shown in that Thing.

Between the festo mod moving all the inputs to the same side (outputs too) as well as giving your fingers more room to work and the helper tool I can load all 5 filaments pretty quickly with little hassle.

Thank you for all the links!!!!!  I'll definitely be using them.

I don't think rewinding spools are necessary if you're using the buffer.  I thought about doing auto-rewinding spools but not sure how well they work and I'd have to print at least 5 of them right off the bat.  That seemed it could be challenging for a first print and it would have to be 2 colors.  So I thought I'd go with spools on rollers and run it through the buffer.

I don't know enough about the way the MMU works to follow your mod.  I'll come back to that later on I think. 

The mod to the filament buffer might be useful, but again I don't know how it works or doesn't work.  I need/want all the filaments coming up from the bottom shelf, into the buffer from the bottom and out the top toward the MMU.  There's a video on youtube of a guy assembling one, but he ends the video before he puts any filament through it.  I really have no idea how you thread the filament through that thing or if it will be possible to mount it on the wall behind the printer.

At this point it might be better to eliminate the buffer, keep the spool rollers and just let the filament buffer to the ground behind the bench?

RE: Filament buffer useful?

Posted by: @vintagepc

My take on your questions for my own MMU:

- Not me,

-A royal PITA, even if not attached to the wall and you need to reach over a table and around a printer.

- I'm running variations of the auto-rewind spool holders in my own dryboxes instead. I consider them a significant QOL improvement. 

https://www.prusaprinters.org/prints/22023-auto-rewind-sistema-5l-drybox/

 

I'm going to get all that stuff on order right now.  Thank you.

RE: Filament buffer useful?

Posted by: @smoking_rubber

. don't think rewinding spools are necessary if you're using the buffer.  I thought about doing auto-rewinding spools but not sure how well they work and I'd have to print at least 5 of them right off the bat.  That seemed it could be challenging for a first print and it would have to be 2 colors.  So I thought I'd go with spools on rollers and run it through the buffer.

There is no reason that the rewind spools have to be multicolor, in fact 2 of the 5 I had were single color. I also started with just 2 and then printed more as I got past MMU issues.

The rewind spools are useful in cases where you don't have room to properly setup the buffer or just don't want to use it. No you would not use both rewinders and a buffer at the same time.

The mod to the filament buffer might be useful, but again I don't know how it works or doesn't work.

The festo mod is useful on a few fronts.

The first is that the stock configuration uses a bolt to compress the PTFE a bit to hold it in place. Too loose and it pops out which causes the filament to bind. Too tight and it adds drag to the filament (drag/friction in the filament path is the name of the MMU experience). The passthrough festo holds the tube securely while not compressing the tube.

The next fix (in my opinion) is that it adds more space to get your fingers in there to guide the filament as it enters and exits the buffer. This makes loading much easier.

Finally it also allows you to move all filaments to one side which makes loading easier if you don't have easy access to both sides of the buffer.

  I need/want all the filaments coming up from the bottom shelf, into the buffer from the bottom and out the top toward the MMU.  There's a video on youtube of a guy assembling one, but he ends the video before he puts any filament through it.  I really have no idea how you thread the filament through that thing or if it will be possible to mount it on the wall behind the printer.

The buffer is a sandwich with space between each divider. Each filament goes into it's own gap. It may be difficult to see it until you have the buffer, but you insert the filament and then feed it to the output side (down in my configuration) on the same side (left/right) as the the input. When the MMU ejects filament during a change it will create a partial loop inside the buffer.

The setup you are talking about is effectively the same as what I have. You would just feed into the bottom of the buffer and it would exit up to the MMU.

At this point it might be better to eliminate the buffer, keep the spool rollers and just let the filament buffer to the ground behind the bench?

The Prusa spool holders are terrible in my opinion. They just don't move well. Use the bearings for holders (rewind or not) you print for yourself.

Letting it "buffer" to the floor is probably a safe place to start, but it isn't viable in the long term. The issue is that the filament will loop itself around itself and anything else to create knots. It works for simple prints that you can keep an eye on after each tool change, but you don't want to leave it unattended.

RE: Filament buffer useful?

I admit I never used the Prusa buffer. I went straight for those auto-rewind spool holders: https://www.thingiverse.com/thing:3338467 (without the filament guide included in that design and unwinding the spool from below, not above)

I did struggle at first with them working reliably, especially the spring. Printing the stiff spring in PETG (setting bridge printing speed very low) worked best in the end (PLA is stiffer and works for some time but breaks easily). However it only started to work truly reliably when I moved the spools from the top of the enclosure to below the printer. I added some self made guiding pillars to prevent filament from rolling up besides the spools but otherwise let the PTFE tubes hang freely.

Friction in this system is very low and the filament is not bent against its preferred direction of bending.

Bottom line: I am very happy with the autorewind solution now but it took some optimisation and a heavy amount of printing the necessary equipment to get it all together.

RE: Filament buffer useful?

@jiral

What do you set your rewinder tension too now and can you share the code so I can print them in petg?

I have all the bits on order except the dry bags.

RE: Filament buffer useful?

@jira

I had trouble however being quite the opposite of most of these posts. By eliminating the drag throughout the filament path all the way to the extruder my spools were knotting and getting worse as the spool emptied.

  There was a backlash condition due to a rocking motion of the spool itself. As the extruder pulls and releases along with carriage movement the filament lost tension and eventually crossed over itself. This condition is worse when using a larger diameter nozzle eg. 0.6mm.

I've reduced the backlash by adding a 5cm loop of PTFE tubing at the entry to the buffer. Without backlash I no longer suffer from knots. The rocking motion is a significantly reduced without loosening enough to form knotting.

 Be safe and stay healthy, 

Phil

RE: Filament buffer useful?

@smoking_rubber

I would recommend not using any foreign gcode in general. While gcode from prusaprinters will be in general fine, you never know and there is quite some potential for problems, even without ill intent. The best is to prepare stl files yourself in the slicer.

As spring I used this file: https://cdn.thingiverse.com/assets/f0/8d/ad/5e/f4/SpringFlat_Stiff_v3.3.STL

Use the standard "0.20 mm quality" printer settings and as filament either PETG or Prusament PETG (I used Prusament filament)
The only setting you need to change is bridge speed. I set it as low as 5 mm/s I think. Just observe the spiral during print, if you see that no nice spiral shape is formed, slow down the general printer speed at the printer itself. After printing you have to break free things, that is a bit tricky, definitely have a look at the instructions: https://www.thingiverse.com/download:7987633

Start with one spring and if it works out, print the others. I would also not print the spring together with the other parts but separately.

I have to set the retention rather high, usually 10-12 but that depends on your specific print. Just try it out yourself.  That also depends on your printer setting however. I reconfigured mine recently and I think I have much better reliability and less issues when the spools are below the printer, compared to above.