Is the MMU2 "ready" and worth it?  

RE: Is the MMU2 "ready" and worth it?

I do not currently own one.  I purchased one with a printer from a guy that could not get it to work (off eBay). I installed it and sold it on eBay.  I do not have a huge need for multicolor prints.  The guy who bought the printer loves it.  

I think your concerns and experience is shared my many purchasers. 

RE: Is the MMU2 "ready" and worth it?

The MMU2S out of the box is not ready. It has two very clear design flaws, which Prusa could fix trivially if they wanted:

• The PTFE tubes shipped with it have a too small diameter. You need to replace them with larger inner diameters - 3mm ID / 4mm OD works great.
• It ships with a printed "bridge" to clamp the feeding tubes to the unit, which is completely unusable. Twisting the screws a miniscule amount too much squishes the tubes, increasing the friction a lot, thus making it very unreliable.

These two points have been demonstrated and discussed ad nauseam in forums (e.g., r/prusa3d which I visit more often than prusaprinters; but I have seen it mentioned here as well). 

Both issues are easily fixed by the user, by buying other tubes, and printing another bridge which uses proper PTFE fittings to clamp the tubes. I assume that 80% of all the incredibly disappointed users are victimgs of these points for either not knowing about, or not caring to do the modification. My unit was not able to do a single filament change before fixing that (the filament did not even pull back into the short tube, even though the tip was pretty well-formed; the tube was so tight). After fixing it, it performed many hundreds of tool change with no hickups whatsoever. And the few multicolor models I printed looked (especially after a few coats of XTC-3D) simply awesome.

Further issues, which may or may not keep it from working, or are just plain user unfriendly:

• The "UI" is a joke. It consists of 3 buttons and 5 LEDs with several states each (red/green/off; the LEDs can be on, off, slow-blinking, fast-blinking). There is near zero documentation on what the buttons do, or what the LEDs mean. Also, in some states the LCD displays some info (but only while a print is running and the printer proper "needs" something from a jammed MMU2S). An alternative firmware which changes the complete structure of these things exists, but switching to a custom firmware is a big step away from the Prusa-archetypical goodness that the base printer is. I personally just read the firmware source code as documentation... YMMV.
• The part where the tube between the MMU2S and the extruder starts is connected is completely closed. If debris gathers up there, and it will, it is close to impossible to clean; eventually jamming the filament detection ball and requiring disassembly. User-designed alternative models which are open are available on thingiverse.
• There is a knife blade which can kind of clean up bad filament endings; it works only so-so and clearly seems like a not very well tested afterthought. You don't really need it, it's just superfluous, but of course as it already is there anyways, it would be mighty find if it works as intended (the idea is a valid one).
• The buffer is just junk, and should not even be unpacked. The idea is OK in principle, but it adds so much resistance to the filament path that it seems unclear whether anybody can *ever* have used it. There are many designs for rewinding spool holders, and a gravity-based with an incline toothed ramp works great. But you can also just have a meter or so of empty space between the rolls of filament and the feeder tubes and let the filament sag when it is unloaded. Just doesn't look good, but is perfectly fine. I had a lot of frustrating entertaining hours printing various user-made rewinder designs which mostly didn't work well if at all before setting to the "sagging" solution, which I am very happy with, now.

Finally, Prusa support basically does not know the MMU2S unit, and the few times I asked them something regarding it, I got no, or wrong answer. It really pains me to say that, because for MK3S or other questions they are a really cool bunch and *very* good.

 I personally keep the unit on my printer, anyway. I found that I don't actually need to print any proper multi-color prints, but I love having 5 filaments constantly connected, and choosing with a few key presses instead of having to move spools around constantly. The MK3S was kind of boring - so perfect, nothing to do. The MMU2S gives me a constant source of problem solving to do. You have to decide yourself if that is worth it to you. 🙂 If you tend to frustration, or are expecting Prusa-level quality, stay away.

RE: Is the MMU2 "ready" and worth it?

I have been printing multicolour for half a year almost non-stop. The only challenges I have are basically due to the fact that I am torturing myself with slightly clogging prone filament and a 0.25 mm nozzle (which is actually not officially supported by Prusa for multicolour). I still manage to do what I want to do, but it is a bit tricky. With a 0.4 mm nozzle however it works now like a charm. I do have those modifications mentioned above however and needed some time to fine tune some other things (IR sensor, loosened screws on the selector).

Having that option to select out of 5 spools, even when printing just single material is something that is quite a nice comfort feature however.

I agree with OutofMuc, it is not an "out of the box" product and you should be ready to face the need for fine tuning or a bit of trouble shooting. It is incredibly wasteful (both material and time) but the results to hold up to what you can find online.

RE: Is the MMU2 "ready" and worth it?

I would say that unless you enjoy building something from a kit from scratch and are prepared to do some tinkering and troubleshooting. This product is not for you. If you build the original prusa from kit and found it enjoyable, or have build some other reprap style printer from scratch, this IS a product for you!... If you bought the prusa assembled (or as a kit and hated it), or only have experience with consumer printers like creality's ender products, this is NOT for you.

RE: Is the MMU2 "ready" and worth it?

I was one of the first people to get the updated MMUs and it was 6 months of tears and bricked my system.  The community came up with some must have upgrades which may or may not be on the current MMUs from Prusa.  I would say 85% of my prints using the MMUs go off flawlessly.  It is worth every penny when it works.  You should be handy person because you have to dial in the Sensors on both the MMU s and the Extruder.

The key things to upgrade if Prusa has not is putting a magnet under the MMUs ball bearing sensor to pull it down. Otherwise any wisp of filament will keep it activated and it will fail. 

The second one is to update filament sensor housing on the extruder.  Several good versions with better alignment features.  Again Prusa may have already added these to his current design.

RE: Is the MMU2 "ready" and worth it?

Posted by: @mikicab

I was one of the first people to get the updated MMUs and it was 6 months of tears and bricked my system.  The community came up with some must have upgrades which may or may not be on the current MMUs from Prusa.  I would say 85% of my prints using the MMUs go off flawlessly.  It is worth every penny when it works.  You should be handy person because you have to dial in the Sensors on both the MMU s and the Extruder.

The key things to upgrade if Prusa has not is putting a magnet under the MMUs ball bearing sensor to pull it down. Otherwise any wisp of filament will keep it activated and it will fail. 

The second one is to update filament sensor housing on the extruder.  Several good versions with better alignment features.  Again Prusa may have already added these to his current design.

Hello, reading your post and finding some frustration with my MMU2S would you be able to please point me at your preferred designs for these upgrades?  I would ave me trying many different ones potentially.  Thank you in advance for the help. 

RE: Is the MMU2 "ready" and worth it?

Two upgrades were essential.  There maybe better or more upgrades but these did the trick.

https://www.thingiverse.com/thing:3725680    

Adds a magnet to the MMU selector.  This pulls the metal ball down.  This keeps a wisp of filament from keeping the sensor triggered.  This was the biggest bang for the buck

IR-Sensor mod with bigger slots for adjustments.

https://www.prusaprinters.org/prints/4932-ir-sensor-holder-mod

I also did an extruder idler mod but don't know if that helped out.  I tried a number of them but I don't think they did that much.  These two upgrades were the ones that made all the difference.  There maybe better versions out there but these worked for me.  The MMU is a must.

RE: Is the MMU2 "ready" and worth it?

The tubes that came with my kit were just fine.

I did the mod to add the bridge with the screw-in PTFE fittings and another to add a switch to cut the power to the MMU to revert it to single-color.  Both pieces are in the prints section.

RE: Is the MMU2 "ready" and worth it?

I have had mine now for about 18 months.  My use case is to have multiple colours available and then just print the item in the desired colour - saves loading and unloading filament.  All I want to do is select the item to print, select the colour and hit 'GO' and walk away.

I have found the unit to be very unreliable.  

It has trouble doing this simple task reliably.  Can't load, jams, can't feed half way through a 5 hour print.

Not worth the grief.  Not ready for sale.  Very disappointed.

Latest problem which I could not fix:

         Will feed to the extruder OK, but when it comes to printing, the extruder is feeding the filament but the MMU2 does not feed at all.

Have just removed it from the printer today.

RE: Is the MMU2 "ready" and worth it?

When it works, it works. When it doesn't, oh boi you'll know it.

Do I have regrets buying it? Nope. It's a handy machine, and I've managed to create some amazing things using it. I do wish Prusa would give us an update on it, though. It does feel like they've kinda swept it under the rug... With Palette releasing the Pro 3, running up to 8 filaments at once...

RE: Is the MMU2 "ready" and worth it?

@andarne

I'm keeping an eye on the Palette V3 Pro as well.   I upgraded one of my two printers to the MMU2S and I have working ... okay, but it doesn't have the level of trust I have in a stock MK3S+.  It's so annoying to have hours and hours of successful tool changes and then an hour where it happens every 15 min but then a few hours of flawless tool changes.  I bought mine MMU2S to do soluble supports, and I have that working now finally, but you REALLY have to have a lot of patience.  it helped having a second stock MK3S+ to print the mods needed to make the MMU2 work somewhat reliably.  As posters above have mentioned I have done the following:

Selector R2 with magnets

The PTFE pass-thru with the Festo connectors

And the 2mm ID 4mm OD PTFE tubes.  I believe I've seen mentioned that the tubes prusa supplies are 1.88mm ID.  This leaves NO room for cases where the filament tip gets a blob on it when it's yanked from the extruder.  Since upgrading my tubes a week or two ago, I've had NONE of these blobbed tips, or at least none that have jammed up my print.  I just completed a nearly 50 hour PLA + BVOH print that had almost 500 tool changes.  I did have to intervene a few times, but it was mostly because the gravity auto rewind spool holder would sometimes pull the filament too far out and it couldn't be grabbed the next time the filament was needed.

To be fair I spent a good bit of time reading this forum and talking to folks on here before my MMU2S arrived.  So I kind of had a clue that it wouldn't be as easy as the the MK3S was at first. 

If you don't have patience be prepared to be very frustrated with the MMU2S.  But it CAN work.

RE: Is the MMU2 "ready" and worth it?

We recived MMU2S week agou and we are trying to make it work reliable.

Quality of printed parts is not great. Some parts needs to be printed with lower resolution than 0,3mm. Especialy front-PTFE-holder. I had to clean and clearance this part a lot. Selector, blade, blade holder were in collision. Too loose brass tubes of selector will not help.

Now everything moves nicely. Before that we had selector errors when printer was changing filament from position 1 to 4 and got stuck at position 3. No error detected.

Now I am solwing why it load fillament to noozle (bit of extrusion happens)  and immediately it will unload it and start loading proces again. FINDA and IR seems to work fine.

Also option for easy bypass of MMU (option in menu) would be great. Sometimes we need to print flex for example.

I would say that in current state is price 299US way to high. Better to spend them on another printer.

RE: Is the MMU2 "ready" and worth it?

^^ Another printer can't do what an MMU can do however and if you dial it in it the MMU works perfectly fine. So the comparison is a bit pointless. The alternatives to an MMU are the Pallete or a the tool changer from E3D with four tool heads it can autoamtically swap. Both are considerably more expensive than the MMU.

The Pallete also has its kinks and limitations but even if it might be easier to dial in it costs app. double that of the MMU2s. Yet it is as or maybe even more wasteful than the MMU. The Toolchanger from E3D is more of a game changer if it works as I would assume it does. For some reason I have not seen a lot of people having or using it yet. It doesn't seem to be for the 3D printer beginner either with its duet board based system.

RE: Is the MMU2 "ready" and worth it?

So even with the i3MK3S+, some issues with the MMU2S still cannot be eliminated and I should not expect that it would work without spending many hours trying to fix things?

RE: Is the MMU2 "ready" and worth it?

@prusanewuser

nope,  you SHOULD expect hours troubleshooting, cursing, etc. 

RE: Is the MMU2 "ready" and worth it?

Posted by: @ssill2

@prusanewuser

nope,  you SHOULD expect hours troubleshooting, cursing, etc. 

If you are naturally impatient, the MMU2S is not for you, period.

If you are willing to spend time reading between the lines, paying strict attention to detail, printing and installing some remixed parts, and general futzing around, yes, you can get one working as expected.

I would strongly suggest the remixed input piece with the bowden tube connectors and the on-off switch which I've previously discussed, for anyone using this.

The buffer is a pain in the @$$, even with the remixed pieces to make it easier to load.  I still have not found a good solution to my particular setup.  When I do a multi-color print I take the whole thing out of the enclosure, set it on the floor of the spare bedroom, and set up the spools way behind the printer to use the floor space as the buffer.

RE: Is the MMU2 "ready" and worth it?

@jsw

I've got one of these printed and I've been testing it today.   it seems like it might be the thing I was looking for

This spool holder
https://www.thingiverse.com/thing:3970400

And the mod to make it fit M10 fittings
https://www.thingiverse.com/thing:4219159

I'm probably going to print a full set of them.

RE: Is the MMU2 "ready" and worth it?

Does that new mini buffer work with the filaments bent at such an angle?

I ran into some issues on the original buffer trying a bracket to hold the input tubes at a 90 degree angle with the radius about the same as shown in that thing.

RE: Is the MMU2 "ready" and worth it?

@jsw

it seems like it does.