RE: MMU2S not ready for public use
I wouldn't recommend the standard e3d heatbreak. I had one before I added the MMU2 as I was unaware of any difference. It contributed to my problems.
RE: MMU2S not ready for public use
Ugh. Had it working perfectly. Then I had a jam due to the issue with the heatbreak around heavy retraction prints and now I can't get the tension on the idler door dialed back in. Tips are stringy again and now it's jamming due to heat creep from the extruder motor because I apparently have the tension too tight.
I'm finally giving up on Prusa's extruder design and have ordered Bondtech's extruder. That will take care of the heat creep issue and I think I'm going to give a normal e3d heatbreak a try too. So here's looking forward to a few months of fiddling again 🙄
For me, there's more sensitivity to the tension screws in the MMU2S than the extruder idler door. But I have loosened my idler door screw, which was installed according to step 32 of the E-axis assembly manual (screw head should be aligned or slightly below the surface), after a Prusa support person told me the screw shouldn't protrude past the nut on the other side. Well, my screw doesn't even engage the spring at that point, so it sticks out of the nut a little. I've never had a problem with the IR sensor, using PLA, PETG, or flexible PVA.
I don't see where Bondtech makes an extruder for the MMU2S, just for the MK3S. Wouldn't you need to modify it to integrate the feed tube and IR sensor somehow?
RE: MMU2S not ready for public use
I wouldn't recommend the standard e3d heatbreak. I had one before I added the MMU2 as I was unaware of any difference. It contributed to my problems.
I actually bought it a year ago as I ran into the retraction issue bad and was about set to rebuild the extruder with the Butterworth mod version. Then before all the parts showed up I got the shipping notice for my MMU so I gave up the rebuild preferring to keep the variables at a minimum.
I definitely wouldn't recommend a new MMU user using any kind of modded extruder initially as that just complicates things. At this point, however, I know the MMU well enough and how it should work that I can debug and work through issues from mods.
As I understand it (I know there was at least one person using the straight break and documented it) you need to play with the retraction settings in the slicer to get it to still form acceptable tips for the MMU.
RE: MMU2S not ready for public use
I don't see where Bondtech makes an extruder for the MMU2S, just for the MK3S. Wouldn't you need to modify it to integrate the feed tube and IR sensor somehow?
If you go to the bottom of the page for it on their site they link you off to a TV designer that has modified the top plate to add a MMU tower: https://www.thingiverse.com/thing:3565326
RE: MMU2S not ready for public use
@gnat
I actually have this setup. I went with bondtech due to heat creep after fan and heat sinks failed to eliminate the problem. As an add-on the screw in the idler door is more "user friendly". In my case i found it out to be the solution to heat creep BUT not a solution to stringy tips. Also keep in mind that its a tad more hasle to remove the hotend since the threaded heatsink is really firmly placed in the extruder. It was a bit of a hassle when i wanted to remove a bad pfte. All in all i prefer it to the prusa one
RE: MMU2S not ready for public use
@jiral
No, its not the IR sensor. I've tested it every time I've taken the hot end apart to deal with this. Every time it jams up, I test the sensor. Plus you can tell that it's working by the movement of the E axis as the filament reaches the bondex set. It stops, does the heating, and then does the push down the the nozzle, and then never stops pushing filament. I reflashed the whole thing, started from scratch (again), remade the PTFE, checked the paths on the MMU, and now it works as long as I don't try and change filaments. Hooray. I have zero faith in it.
Also RE the person with the snide comment about wasting time with complaints. I can tell you my ratio of searching for answers to time complaining. 10 minutes writing a complaint after 60~ hours of working on this thing gives a complaints to work (reading trouble shooting, surfing around etc) of 4.62x10-5 to 1. Also blame the person having problems much? Please don't reply again. Am I complaining now? I'm sure my ratio is getting worse by the second. ._____.
I'm so good at taking apart hot ends now. I can do it in about 15 minutes flat (including heat up and cool down times.) I honestly don't think that's the way it should be. If you think the MMU is some kind of proof of Scottsmanship in the 3d printer world, I'm pitying you. Why else would you defend a thing that doesn't reliably work? Would you be happy with a car that popped out of gear 30-50% of the time when you came to a stop sign and then required 15 minutes spent fiddling around with it? I certainly wouldn't appreciate it.
The whole idea of crowd sourcing a product by using consumers as beta testers seems pretty crappy to me. This is what the MMU is, it is a crowd sourced thing that doesn't yet work very well.
For over $1000 the i3 Mk3S MMU2S is a failure as a product.
Eventually I will get this to work, but I won't recommend it ever.
Does the Mk3S make beautiful prints if I treat it as a single filament machine? Yes, when it works, it looks amazing. My first layer setup is measurably correct at exactly .2mm for a .2mm 9 square test on all 9 squares. Adhesion is amazing.
Design wise, I think it has serious flaws. The PTFE tube seems overly complex, and is source of problems. The channel guides for the filament in the MMU only have centering cones in one dimension.
I was describing the problems of this machine to my wife, and I explained it as similar to a one sensor ice maker, but not being precise enough to work in such a manner. Ice makers in refrigerators use a single temp sensor to operate by measuring how much the temp changes when water is added to figure out indirectly how much water has been added. The filament sensor is like this, a single sensor, but it is binary, not a range value. It detects filament at a single point. Wouldn't it have been better to put the IR sensor to reading a slotted wheel that was driven by the passage of filament? You could detect exactly how much filament went by, you could tell if it was jammed. You could know exactly how much the bondex gears were slipping. If you wanted more precision you could add more slots. If you had a 1cm idler that was driven by passage of filament and 50mm slotted wheel with 30~ slots it would render .5mm filament passage resolution. It would allow for much smarter programming of fail safe. This is impossible right now. You can detect that the filament entered the bondex set, but if there is a problem below that, you can't tell. Without analogue data about filament passage the whole thing is a crap shoot. Without detecting actual passage of filament you depend on a whole host of filament related things being perfect or close to perfect. This is not a robust design, and it shows. This is why there so many search results about the MMU not working. Systematically speaking, adding the MMU adds at least 7 filament transition points that can go wrong. Murphy's law says, what can go wrong, will, and in this case it does. Considering that the MMU itself will grind the filament and cause a problem down the line is huge. If it had filament motion you could write start code that tried to move 2 mm, and if it worked, you could move more. I'm digressing.
Meh. I'm already regretting this post.
-Ira
^^ The extruder door should be printed out again, or you may try lengthening the tick or latch—or whatever you want to call it—such that it is slightly too long so that it always triggers. Then, like gnat mentioned, you sand it down gradually until you have a senser on/off feedback that works equally well with hard and soft filament. Once you've done that, any IR sensor problems and hiccups should be history, and the sensor should be resistant to a wide range of different screw tension settings.
RE: MMU2S not ready for public use
I am focused on getting the tips right. Using PETG and getting long stringy tips. Added cooling moves to 4/5, and reduced temp.
I too, eliminated the buffer. I bought the RMU, but found it cumbersome to use. Have my spools set up to use the most spread out configurations possible, and position the spools 10" apart. So far, no entanglement.