Direct-drive MMU "Camstruder"
Hi together,
I registered to this Forum to get some thoughts or maybe even a "Wait, I'm already working on that!".
As an owner of a i3 MK2S, I'm thinking about getting a MMU upgrade about once a week. But as the one who implemented the LIN_ADVANCE pressure control, I can't convince myself to get a bowden system.
Therefore I'm creating ideas how I could combine the one nozzle system with a direct drive extruder since quite some time. Two concepts are in my mind:
- A system which could be added to each direct drive system, containing of an extra stepper motor per color/material for retraction and insertion. Material change would take the following steps: Retract the filament by extruder stepper until it's above the hobbed bolt. Retract by filament change stepper to a cutter unit. Cut the molten end, push out the cutted tip with a bowden segment which can be pivot away and finaly retract behind the Y splitter. Insert another filmanet by another filmanet stepper motor. A lot of steppers and system components needed, which means a lot that can fail. Would end up compairable to the palette.
- Second, and that's what I want discuss here, something what I call a "Camstruder". This extruder stepper would sit above the Prusa MMU splitter element, while two (one for left two filaments, one for the right ones) servo driven camshafts select which filament to grip and which should be locked in place.
I designed such an extruder for my TAZ5 (see here), but due to some issues there I never built a complete one of these. But the Prusa MMU solves the issues, the filament shaping splitter is in place and we have much more flexible 1,75mm filament. With this, we could save the bowden "workaround", 3 stepper motors and the multiplexer board.
Build space to left and right of X axis will be challenging, but it might be possible. Depending on the feedback, I might try to design such a thing during winter.
Re: Direct-drive MMU "Camstruder"
Hi Sebastian
I currently run 2 Mk2/S printers, both with MMU. KISS takes into account the extruder geometry and filament characteristics with "PreloadVE" values. So far, I have found very little difference between the direct and bowden systems. I intend swapping the Bowden tubes for Capricorn in the near future.
Although I don't tend to customise the printers very much, I would be willing to assist you with this project and customise one of the Mk2 MMU printers I have.
roman.t may be another PR owner willing to help out - certainly worth asking him. We were both involved in the MMU Beta test program and I have written a KISS post-processor.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Direct-drive MMU "Camstruder"
I intend swapping the Bowden tubes for Capricorn in the near future.
This seems like a great idea. Are you intention to use the XS Series?
What is your opinion of using the XS Series inside the HotEnd as well?
Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage or loss. If you solve your problem, please post the solution…
Re: Direct-drive MMU "Camstruder"
This seems like a great idea. Are you intention to use the XS Series?
What is your opinion of using the XS Series inside the HotEnd as well?
Yes; the problem is that I think the ID is 1.9mm and not the 1.85mm required to form the tip during unload; it may work, but I was much more interested in reducing the play in the Bowdens.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Direct-drive MMU "Camstruder"
Yes; the problem is that I think the ID is 1.9mm and not the 1.85mm required to form the tip during unload; it may work, but I was much more interested in reducing the play in the Bowdens.
Peter
FWIW, I put the XS in my hotend and printed the "Knight of Egypt" (50 hour print at 0.15mm) with no jams.
Edit: The Capricorn website lists the ID as 1.85mm.
--Colin
Re: Direct-drive MMU "Camstruder"
FWIW, I put the XS in my hotend and printed the "Knight of Egypt" (50 hour print at 0.15mm) with no jams.
Initially I was printing fine with a regular 2.0 ID PTFE tube without issue.
Edit: The Capricorn website lists the ID as 1.85mm.
Yes, and other sources state 1.8, 1.85 and 1.9. Seems to imply that the ID varies.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Direct-drive MMU "Camstruder"
OK, we need to get back on topic...
Sebastian, been having a think about this.
I don't think there is any need to cut off the filament tip on unload, so I think it may be worth going down this path:
The tip needs to be formed on unload but below the primary extruder. Roman.t has a printer which cools the filament within PTFE tubes instead of the PR SS ones. The Prometheus extruder also cools the filament in a PTFE (?) tube. As far as I can tell, there may not be any need for anything more than a single PTFE tube below a direct drive extruder stepper for tip forming/cooling.
So that just leaves the question of how to change filaments. I would think that it would be possible to park each filament above the primary stepper and have a second stepper above this to load and unload filaments. Ideally only a single stepper which uses cranks to engage the correct filament drive.
Should not be too difficult a task for those clever guys out there...
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Direct-drive MMU "Camstruder"
Yes, and other sources state 1.8, 1.85 and 1.9. Seems to imply that the ID varies.
Peter
E3d-online.com sells Capricorn tubes https://e3d-online.com/capricorn-bowden-tubing and they list it with 1.9 ID
And the specs for Premium XS Series Dark Blue Tubing shows: ID 1.9 +/- 0.05 https://www.captubes.com/specs.html
Re: Direct-drive MMU "Camstruder"
E3d-online.com sells Capricorn tubes https://e3d-online.com/capricorn-bowden-tubing and they list it with 1.9 ID
And the specs for Premium XS Series Dark Blue Tubing shows: ID 1.9 +/- 0.05 https://www.captubes.com/specs.html
Just measured - 1.89/1.94 at one end, 1.93/1.97 at the other. So it should be better than regular 2mm Bowden tubing, but perhaps not small enough for the extruder.
Peter
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…