Found some photos of the new Prusa MMU v2 internals. Wish I was there to see it in person. Seems to be a very clever method and hopefully good reliability
I’m curious if they have a “no press” idler position on the rotating idler part so the media can be fed normally from the main drive, without having to synchronize the two hobs or drag against a deactivated idler
An early review.
I love this new setup, it’s direct drive unlike it’s bowden predecessor and it has the potential for expansion (more than just 4 filament feeds).
@Xiaojun_Liu The middle motor in the first picture turns a hobbed shaft (for the 4 filaments), the top motor rotates a cylinder with embedded bearings so only the filament that you’re currently using is pressed against the hobbed shaft by the bearings, and the bottom motor moves the feed tube along the lead screw to select the driven filament. The selected filament then gets pushed down to a direct drive extruder.
Looks over complicated to me. Just do a tool changer.
How exactly would one make a simpler tool changer that works on a Prusa I3 frame that’s less complicated than this?
Perhabs the i3 frame is not the best choice for multimaterial. Doing tool change on a core xy cube frame is easy.
But this allows for multi material on an i3 frame. Thus it has sufficient complexity for what is needed and a tool changer won’t work. This is also significantly cheaper than a 5 tool CoreXY capable of the same print quality.
I own the multimaterial prusa i3 v1. And it sucks. This concept does not fix the problems, which are all related to the idea of pulling back the filament for changing.
This actually does do things to fix the problems. Converts it from Bowden to direct drive. Improves the filament path from feeding to nozzle, removing the branches that could get pieces stuck. Adds an additional material with the same number of motors.
The mmu v1 was doomed from the start. People have tried that split path concept before and it was never very successful. This has more potential to be reliable with very low cost components. You could even do crazy things like adding a knife to the linear axis to trim off any dangling pieces of filament.
Tool changer is more reliable but prohibitively expensive for most consumers. If they can work out the bugs this has good potential at a low cost.
Complexity is relative
I have the MMU v1 and I get pretty decent results. It’s definitely not as reliable as the MK2 is alone but I’ve gotten 30+ hr prints with no issues. Although I have started drying my filaments before doing a multi-material print, I find any moisture in the filament can expand it just slightly enough to produce jams.
It works ok if all you want is multicolored pla prints. I wanted to combine materials for functional designs and use solible supports. Turns out it does not support flexible materials and probably never will. My other i3 clone is also a bowden and it can do it. The prusa can too, just not in multi material mode. Also support for other slicers is lacking.
I also want to add that there is nothing cheap about prusa i3.
@Baldur_Norddahl I disagree. I’ve used it to print PVA at 215 C to support XT-CF20 at 260 C. I’ve also been able to run Cheetah filament through it, I even did a 14 hour print with just Cheetah.
As far as cost goes Prusa’s printers are more expensive than the clones because they’re made with genuine parts, have consistent firmware updates, and have more features (like mesh leveling, TMC2130 drivers, automatic XY skew compensation) that allow it to perform better. When you purchase their printers you’re also contributing to all the development they do which is released as open source to benefit the community as a whole. Sure purchasing a MK1 i3 from Prusa over a clone might not have made much sense but the MK2 and MK3 are the most capable i3 derivatives on the market.
Oh yes! More pictures of the MMU2 
Again cheapness/Low cost is relative and if you compare quality of components, firmware, slicing, and support of the Prusa i3 mk2/s3/3 it is most assuredly cheap. Ultimaker is the only printer that comes close which is over twice the cost
My anycubic i3 mega has a better build surface than my prusa i3 and prints just as well in any other regard. The anycubic therefore gets used more. Sorry guys, I know it is an unpopular opinion, but I do not see that paying more than twice for the prusa got me much here. Yes technically the prusa has some features such as auto bed leveling, but in practice the anycubic does just fine without it. Print quality is identical.
Regarding PVA this does indeed work fine with multi material, but I suppose I am disappointed with the filemant or maybe the way Slic3r uses it. Interface layers is not as good as it should be. Also I want to use Cura but MMU forces me to use an inferior slicer. Not very open here.
Using Ninjaflex, TPU or even the Flexfill 98A I got directly from prusa is completely unsupported and does not work with MMU. Flexfill will work if not printing in MM mode but the other two are impossible to use on the prusa with MMU installed. I can print both Ninjaflex and TPU on the anycubic and that printer is also a bowden setup.
