Printing head suggestion
So look - I’m not the expert here at all, and I think the real experts over at Prusas have done the best they could. This didn’t stop me from being a creative mind though, which led to this spontaneous post here on this forum:
My idea resulted from the hotend being exchangeable by simple disconnecting it from the responsible daughter board and pulling it out of the print head. Now, as far as my understanding goes - I’ll remind you here, that I’ve not owned a Prusa XL yet - the only additional thing in the filaments way to the printing surface is the filament pulley, right? So why exchange the whole print head including the expensive electronical and mechanical parts, when you could just exchange the hotend for a new one? I imagine it that way: The supply tubes and the hotend are fixed together using some simple structure. Now the print head comes along, the the supply pulley loosens the grip on the filament by simply sliding a bit backwards, the hotend-supply-tube-structure gets hung into the respective storage space to cool down, the print head moves to the next needed hotend-supply-tube-structure and grabs it by moving the supply pulley forward again. In simple terms: The filament exchange is accomplished by sliding the hotend with the loaded filament into the print head and the supply pulley grabbing on to it.
I could imagine this driving down the cost for another "print head" by a lot. So why not use it? Again: I’m not an expert I’m just imagining. And I can imagine there being a lot of reasons no one did that in the first place too.
If any questions remain: Comment, I’ll happily be proofen wrong or agreed with!
Much love, Gregor
RE: Printing head suggestion
Sounds like a different way of doing the MK3s MMU…
F the MMU and any idea close to it.
You want cheaper version of multi material that doesn’t work? Buy an MMU. It is a hobby unto itself.
I don’t want to be mean, but the method of swapping material has to bone simple and repeatable. “Cheaper” ends up costing a heck of a lot of time and money for the swear jar.
Every filament at a minimum needs its own drive system that is in constant contact with the filament. I’d also like each filament to have its own nozzle.
RE: Printing head suggestion
You want cheaper version of multi material that doesn’t work? Buy an MMU. It is a hobby unto itself.
Amen, brother.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
RE:
Sounds like a different way of doing the MK3s MMU…
No, I’d argue it’s absolutely not "a different way of doing the MK3s MMU". My idea was to spare those parts duplicated with every new print head except for the filament supply tube and the hot end (including the attached nozzle). Because latter was, as far as I understood it in the trailer, switchable very easy by design.
“Cheaper” ends up costing a heck of a lot of time and money for the swear jar.
And no, I also don’t think it would require a lot of effort to maintain, as the filament isn’t grabbed by itself, but is held by this hotend-supply-tube-structure and is therefore standardized, meaning easy for the supply pulley to grab. The only way the print head would interact with the filament by moving it using friction of the supply pulley like it always has been.
But thank you for your post! 🙂
RE: Printing head suggestion
MMU works for some people
This printed overnight
they were printed face down so I have turned one over to see the detail
these items below were printed yesterday. 
the Dark Blue was too dark and appeared over extruded, so I changed that filament out for grey blue, and reduced the extrusion multiplier. when re printed the grey blue didn't look right in the bullet splat! so I used a negative volume to put the hole through the bullet splat, and turned the prints over to get a smoother face surface.
these prints are PETG, the red and black are Old Chinese filament other colours are prusament
the items below were printed a couple of days ago, using a Silk Powdercoated build plate (Washed with Dish soap and water, no other surface treatment), turned printer on, loaded filament, selected Print file from SD card, walked away, returned to completed prints that had released themselves from the build plate, no failures to feed, no interaction needed (the caravan that the printer is in, is unheated)
My MMU1 still works too...
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
RE: Printing head suggestion
I don't know why my MMU doesn't work. I massaged out all the PHYSICAL problems, but that just makes the control/logic ones stick out more. Feed and sensors all work, but for some reason my MMU2s 'forgets' where it is and moves the wrong filament. For some reason, it doesn't go through a position check and zero step. Weirdest thing. I assume the XL will know what head it has one it... Plus the MMU, like all "Bowden" systems, struggles with flexibles.