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Move the MMU to the Z axis?  

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gnat
 gnat
(@gnat)
Noble Member
Move the MMU to the Z axis?

I have long intended to move my MMU off the printer if I ever get around to building an enclosure for it, but I was just watching the printer do it's thing and got to wondering about another possibility.

What if you remodeled the Z carriages to have extensions so that the MMU could be mounted on them? I'm kind of envisioning a cross bar in front of extruder (obviously out far enough that the extruder wouldn't hit the MMU) and the MMU would be horizontally fixed (e.g. not moving with the extruder).

My thinking/reasoning is that it would allow you to have a significantly shorted MMU->Extruder PTFE which should have three benefits. The first is that it would reduce the time for a tool change as the filament has a short distance to travel. The second is that is that by having less filament to back out, there should be less need for a buffer/rewinder. The overall placement would also make the MMU easier to access (especially in an enclosure) when needed.

For the time difference, a few seconds per tool change would add up rather quickly on a change heavy print. For example on a 90+ hour print I did with 2407 tool changes, even a reduction of 2 seconds per change would have added up to almost 1.5 hours of savings.

On the ejection difference, if it is indeed enough to allow for the removal of mechanisms to deal with the ejection, that would allow for simplification of the filament path. Simplification of the filament path should help with the reliability of tool changes.

Issues I can see with such a setup:

  • It makes it more difficult to get to the extruder when needed.
  • Can the Z steppers handle the extra weight of MMU?
  • How to counteract the lever effect the MMU's weight will have for tending to pull the Z screws towards the front of the printer? The factory setup of the Rambo and PSU complicate simple solutions.

What other reasons am I missing that would make this a bad/unworkable idea?

MMU tips and troubleshooting
Stop SL1 tank leaks with a simple o-ring...
Posted : 10/07/2020 7:39 pm
jsw
 jsw
(@jsw)
Noble Member
RE: Move the MMU to the Z axis?

My concern is that it would be too much mass for the Z drive and might contribute to premature wear.

The entire mess of input tubes to the MMU will also be moving vertically during the print.

Posted : 10/07/2020 11:50 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: Move the MMU to the Z axis?
Posted by: @gnat

I have long intended to move my MMU off the printer if I ever get around to building an enclosure for it, but I was just watching the printer do it's thing and got to wondering about another possibility.

What if you remodeled the Z carriages to have extensions so that the MMU could be mounted on them? I'm kind of envisioning a cross bar in front of extruder (obviously out far enough that the extruder wouldn't hit the MMU) and the MMU would be horizontally fixed (e.g. not moving with the extruder).

My thinking/reasoning is that it would allow you to have a significantly shorted MMU->Extruder PTFE which should have three benefits. The first is that it would reduce the time for a tool change as the filament has a short distance to travel. The second is that is that by having less filament to back out, there should be less need for a buffer/rewinder. The overall placement would also make the MMU easier to access (especially in an enclosure) when needed.

For the time difference, a few seconds per tool change would add up rather quickly on a change heavy print. For example on a 90+ hour print I did with 2407 tool changes, even a reduction of 2 seconds per change would have added up to almost 1.5 hours of savings.

On the ejection difference, if it is indeed enough to allow for the removal of mechanisms to deal with the ejection, that would allow for simplification of the filament path. Simplification of the filament path should help with the reliability of tool changes.

Issues I can see with such a setup:

  • It makes it more difficult to get to the extruder when needed.
  • Can the Z steppers handle the extra weight of MMU?
  • How to counteract the lever effect the MMU's weight will have for tending to pull the Z screws towards the front of the printer? The factory setup of the Rambo and PSU complicate simple solutions.

What other reasons am I missing that would make this a bad/unworkable idea?

I think that this massive expenditure of changes certainly has a bad effect on the stability of the mechanics and this is in no relation to the time saved when changing filaments. There I would rather optimize the loading/unloading speed. Furthermore, the MMU2 works more reliable the less heat it is exposed to.

But the idea is interesting.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen....
Posted : 11/07/2020 12:26 am
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