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Clarifications about PTFE tubes on MK3S with MMU2  

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Antimix
(@antimix)
Estimable Member
Clarifications about PTFE tubes on MK3S with MMU2

Dear Prusa,

it is not clear to me what are the official PTFE tube parts to be used one there is a MK3S with a MMU2S.

I say that because there are a lot of posts about the Prusa PTFE tube diameters, but there is no official statements on the MMU2S Kit assembling manual. I ordered a Prusa Assembled MK3S printer, so I assume it had the correct tubes installed.

However when it was time to assemble the MMU2S and update the mk3S then doubts raised.
In details somewhere in a Prusa document exists about PTFE tubes, and it say that:
PRUSA MK3S HOTEND PTFE is 1.85mm internal diameter if it has to be used with an MMU2S

I did not install on my printer. 😮  There is no mention of dismounting the Aluminium cooler and replace the inside PTFE tube with this kind of specific type of tube on the document "I3MK3S update to MMU2S".

MK3S and MK3S with MMU tubes are different.

The reason why I would expect that this info should appear, is because in another place PRUSA say that on the I3MK3S (alone) the PTFE tube is clearly different:

As you can see PRUSA HOTEND PTFE is 2.0mm internal diameter if it has to be used with standard alone i3MK3S (no MMU) 🙄 
If you look carefully the drawings, the MMU2 PTFE has as difference a smaller (?) diameter with a small conic cut in inside direction, to facilitate the entrance of a larger tip.

Then I carefully examined with a lens all my PTFE tubes and are surely almost all i3MK3S-MMU2 tubes, since they have all small diameter, even if I can't recognize any small trim flare in inside direction on the tip, and this will not help a filament head blob to enter in the tube 😐.
However only one has a larger diameter, probably 2.0mm, so I assume it is a MK3S only tube.
I can't say from what I got the tubes, I did not label them. Some where taken from the Prusa box as spare, some others in the MMU2S kit, and some were ordered on the Prusa Shop, but I did not remember what kind they were (look at them on the shop, have also a wrong picture...).

The PTFE tube from Extruder to MMU2 is also 2.0mm diameter

So, at this point I would kindly ask to PRUSA:

  •  is the Aluminium Cooler PTFE tube change a requirement ?
     if it is, please document all the replacement phase clearly in the KIT INSTALLATION MANUAL (there is no mention now)
  •  why the metal heath break is 2.0mm and you have decided to shrink the PTFE tube to 1.85 instead of leaving the old 2.0mm diameter ?
    This diameter change is causing a lot of jams because the filament head cools and shapes itself in a 2mm diameter blocks, and once is fitted in a 1.85mm diameter tube it jams... 🙄 😟
    I would have expected an E3DV6 modified heath break, from 2.0mm to 1.85mm leaving the PTFE at 2.0mm, so that a filament head of 1.85 could fit easily in 2.0mm and for all the rest of tubes that are always 2.0mm .....

I hope that PRUSA will explain us the reasons behind, we are curious as makers... 😊 
Regards

This topic was modified 2 years ago by Antimix
Posted : 20/06/2019 8:21 pm
Dave
 Dave
(@dave-11)
Eminent Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

Excellent clarifying questions. Prusa, please address this -- none of it is criticism. Great point about the heatbreak, tip size, and jamming in the smaller diameter tubes. Maybe some change in the heatbreak/PTFE tube dimensions, as well as 2mm ID tubes all around, might solve most of the problems. I haven't assembled mine yet (just finished the printer)... thinking about replacing all the tubes up front with 2mm ones for intial assembly.

Posted : 22/06/2019 3:22 pm
stoofer
(@stoofer)
Estimable Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

You're unlikely to get an answer here.  They respond to comments in the online manual, add a comment.  Or contact support.

2mm ID tubes are the most common. Prusa changed them to 1.85, so they did so for a reason even if we don't know what it is... There is a change in the ID of the Prusa specific e3d heatbreak from the normal v6 one, I posted a photo in another thread.  I was constantly getting wide tips formed that would not reload until I changed to the Prusa heatbreak and I've had no jams since.

Posted : 25/06/2019 12:43 pm
JoanTabb
(@joantabb)
Moderator
RE: Clarifications about PTFE tubes on MK3S with MMU2

I believe the smaller PTFE size is used to help re-form the tip diameter  during tool changes (filament changes) when filaments are unloaded back to the mmu2 holding zone, 

1.85mm should cover all good filaments ( biggest quoted variation that I have noted is +- 0.05mm   = 1.70mm to 1.80mm) bigger than this is way out of spec...

 

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 : 25/06/2019 1:15 pm
CybrSage liked
davidsteinman
(@davidsteinman)
Active Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

I noticed this problem yesterday.  One of my filaments would stop extruding in single filament mode.  So, I took a part the hot end and figured I would need to replace the PTFE tube.  When I found my spare, it's internal diameter was smaller than the one I had in there.  I wasn't sure which one to use.  But since my MMU2S was working fine before, I put the larger one (2mm ID) back in. 

I have MK2.5S with MMU2S and I have replaced the heat break with the newer one.

I guess I will try the 1.85mm tube sometime.

David

Posted : 25/06/2019 1:57 pm
stoofer
(@stoofer)
Estimable Member
RE: Clarifications about PTFE tubes on MK3S with MMU2
Posted by: joan.t

I believe the smaller PTFE size is used to help re-form the tip diameter  during tool changes (filament changes) when filaments are unloaded back to the mmu2 holding zone, 

1.85mm should cover all good filaments ( biggest quoted variation that I have noted is +- 0.05mm   = 1.70mm to 1.80mm) bigger than this is way out of spec...

 

regards Joan

I think this is correct. I wonder what the tolerance for the PTFE tube is, though, as +-0.05 on that could well spell trouble should you have the smallest end of that range. My 1.9 Capricorn (which has tolerance of +-0.05) is working like a champ. I've had one failed load since switching to this and the new Prusa heatbreak, and that was due to stringing getting caught up in the FINDA.

Posted : 25/06/2019 4:18 pm
JoanTabb
(@joantabb)
Moderator
RE: Clarifications about PTFE tubes on MK3S with MMU2

the MMU2 + mk3 setup, is a complex set of inter related  components. 

My belief is that all items need to work in harmony, for overall success

our over riding desire is to Print successful models, 

the Mk3 printer attempts to do this with a direct extruder mounted on the X carriage.
this relies upon a pair of hobbed wheels, to move the filament.

the hobbed gears have a limited ability to move the filament.  
obviously the extruder liner, heatbreak and nozzle MUST be clear of debris and burned filament, in order to permit free flow of the molten filament. the heater / thermistor need to be working efficiently and have been PID tuned the prusa firmware has a set of reasonable good values, but pid tuning via the LCD menu can improve on that.
the spring pressure on the filament needs to be 'just right' and that's probably lighter than you think....

above the extruder, you need as little friction as possible, so make sure all of the filament holes in the mmu2 assembly are clear of strings and deformations. and that the PTFE is free running on the filament.  ALL of my PTFE above the extruder is 4mm outside diameter, and 2.5mm inside diameter.and the lengths are cut to suit filament holder placement, so that the bends are as large a possible radius, without excessive bending.    I have never used the prusa bendy arm filament buffers, my filament rolls are on the shelf above the printer
the right hand picture was taken before I changed the orange ptfe to 2.5mm inside diameter
each filament tray has a short stub of ptfe through a hole in the shelf, (this prevents the filament back feeding to the roll and tangling...) then the main length of ptfe is JUST  long enough to reach the mmu2, in a gentle curve...  minimising friction. 
there are two printed ends for the PTFE on each filament feed, in the picture, just below the yellow roll, there are a red end and a blue end touching each other, this is the filament currently being used, all the rest of the rolls have a red end on the short ptfe through the shelf and a blue end on the longer ptfe to the MMU2.  the filament that is not being used, forms a natural curl between the ends of these two tubes, there are no rewinders on the roll holders, they are not necessary..
 the roller rails are small diameter, so I added additional rollers to reduce friction

I hope this helps people see how i set my printer up... (I am currently supposed to be doing the mk3s/mmu2s upgrade but I dont expect to use the Prusa buffers.)

in the first picture, you can see my mk2/mmuv1 setup to the left of the workbench, which uses similar filament feed setup.

 

regards Joan

This post was modified 2 years ago by JoanTabb
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 : 25/06/2019 9:40 pm
gnat liked
toaf
 toaf
(@toaf)
Noble Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

and now we know what Joan's mad scientist lab looks like 😀 

I have a Prusa,therefore I research....
Posted : 25/06/2019 9:57 pm
CybrSage liked
JoanTabb
(@joantabb)
Moderator
RE: Clarifications about PTFE tubes on MK3S with MMU2

and that was a tidy day! Mwa ha ha haaa!

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 : 25/06/2019 10:00 pm
CybrSage liked
toaf
 toaf
(@toaf)
Noble Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

100% better than mine workspace, but my prusa mmu and spools is on a cart. I can roll it to a corner.

 

tidy....guy style!!!

I have a Prusa,therefore I research....
Posted : 25/06/2019 10:03 pm
JoanTabb
(@joantabb)
Moderator
RE: Clarifications about PTFE tubes on MK3S with MMU2

there is now a Lee, ammunition loading press on the right hand corner as well... for my other expensive hobby...  Lol

 

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 : 25/06/2019 10:19 pm
CybrSage liked
toaf
 toaf
(@toaf)
Noble Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

don't get me started, just ordered my railcoreztl. with parts to mod it to 600/600/600

I have a Prusa,therefore I research....
Posted : 25/06/2019 10:21 pm
CybrSage
(@cybrsage)
Honorable Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

One thing Prusa should change in all MMU2s' going forward is to change to a 2.5mm ID tube size for everything but that one small piece in the extruder.  I just ordered a bunch and will replace mine to make it even smoother.

Posted : 26/06/2019 2:41 am
toaf
 toaf
(@toaf)
Noble Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

yes the ID bigger does seem to help some things for people.  it cant hurt.

I have a Prusa,therefore I research....
Posted : 26/06/2019 2:43 am
CybrSage liked
PrintingD
(@printingd)
Active Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

I would like to give this a try as I have seen filament get clogged in the tubing.

First question: what diameters do people recommend? Some say 2.5mm, some say 3.

Second question: I will need new festo connectors, right?

Third question: can people post reliable sources for these parts in US?

 

Posted : 07/06/2021 10:08 pm
JoanTabb
(@joantabb)
Moderator
RE: Clarifications about PTFE tubes on MK3S with MMU2

I would order, what was easily obtainable either 2.5 or 3,  either will pass filament more freely than the standard 2mm ID. the Festo's are all intended for 4mm OD ptfe  the only time you need to buy new festo's is if you need 'passthrough' connectors. or if the end of your PTFE gets stuck in the festo, and you cannot remove it. 

personally I ordered 2.5mm ID PTFE for my MMU2S

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 : 07/06/2021 11:10 pm
PrintingD
(@printingd)
Active Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

Update: I found ID 3.0 and got it for cheap. It was completely transparent, which is nice because it is easier to see filament and importantly to see filament tips. I am not sure if this was NEEDED, but it sure is cool. If the tips are bad, they will still have problems higher up in the system depending on how many other things are modified in your MMU2.

https://www.amazon.com/gp/product/B07F5Y284C/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Posted : 30/06/2021 7:51 pm
JoanTabb
(@joantabb)
Moderator
RE: Clarifications about PTFE tubes on MK3S with MMU2

@printingd

Has the looser PTFE Helped? 
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 : 30/06/2021 8:05 pm
PrintingD
(@printingd)
Active Member
RE: Clarifications about PTFE tubes on MK3S with MMU2

I think it is helpful, but it is not a solution by itself. The thing that changed everything for me was dialling the total ramming time to 3.0. After I did that all of my tips were good and no more jams. I’m sure having the wider PTFE did not hurt.

Posted : 30/06/2021 8:10 pm
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