[Closed] new mk2s MMU upgrade received for my mk2s  

Re: new mk2s MMU upgrade received for my mk2s

finally, it's the same for my, it doesnt work.

here's my mail to prusa :

***************
Hi,
I've received the upgrade. built it, tried to print the multicolor marvin.
extruder 1 : pla silver received with my mk2s
extruder 2 : pla red (ice filaments)

extruder 1 jammed after 4-5 color changes

2nd attempt. same problem.

one filament gets jammed into the multiplexer, before steel tube. I've measured the diameter of the filament extremity because of heat / retraction : 2mm, the steel tube is 1,9 mm so it cannot retract.

seems like the multiplexer let the filament grow to much while retracting, when it gets out of e3d ptfe tube and just before multiplexer steel tube.

e3d ptfe tube is 1,9, same as steel tube, so the pb seems to be the part of multiplexer where there is no 1,9, diameter.

what do you propose for me to make it work ? is there a new multiplexer ? I dont want to ask prusa to get the product back, because I'm sure there is a simple solution for this.

thanks for your help.
****************

Re: new mk2s MMU upgrade received for my mk2s

If jamming at the steel tubes : Try reducing retraction to 35mm and retraction speed and derectraction speed by 50%.

Solved the problem for me.

Rgds Vinc

Re: new mk2s MMU upgrade received for my mk2s

yes it jams on the steel tubes, because the pla retracted is sometimes 2mm, but when this happens it should be able to go back in the e3d ptfe and in the melting point.

the mmu e3d ptfe tube is 1.9 mm diameter, so the retracted pla cannot go back thru heat break.

the e3d ptfe before the upgrade is a 2mm diameter, on my mk2s original...

I just cutted a ptfe with 2mm internal diameter (one of the ptfe provided with the spool holder, and replaced it.
seems to work fine, I managed to print the 2 colors marvin without problem.

Now I'm testing the other parts provided on the mmu drivers, I'll keep informed of the results.

Re: new mk2s MMU upgrade received for my mk2s

I recommend reading the 28 page long blockage thread. The diameter difference is intended, primary filament shaping location is in the hotend (and not the MMU).

Re: new mk2s MMU upgrade received for my mk2s

I will read it, but with this modification I was just able to print the multicolor gears, without any single problem.
so I'm waiting for some explanations on this.
before this, I had 2 jams in the multiplexer. the filament at the extremity was 2mm about, it cannot go back thru the steel tube.
but it cannot go thru the ptfe.

what seems to happen :
-I have 4 colors, red is printing
-red change color, retraction, the filament occurs to be 2mm, because it stays in the multiplexer, but the other filament can be changed.
-back to this red filament that waits in the multiplexer, behind the 4 junction and before the steel tube, if it cannot go thru the heatbreak ptfe, the print is jammed, and what I did is to allow it to go back.

the total retraction of 4 filaments after the gear printing worked, I did it 2-3 hours after the gear's print end, back from work.

sometimes, a different idea solves the problem, I could be wrong in my ideas of the solution, I'd really like that someone that have some jamming problems tries what I did.

Anyway, I'll go furtger with a much longer print and report here.

Re: new mk2s MMU upgrade received for my mk2s

I've been there. The pre-sliced MM gears was pretty much the only model I could successfully print for months. They either use better retraction / unload settings or the model itself is just ideal for the purpose (good show-off, not many retractions). If your system doesn't block on color changes, that is. It is really misleading because you think your printer works.
But everything else was undoable (even the gears when I sliced them myself using default settings). My advise is, read the forum thoroughly and make notes. A few hours work, but it will save you many frustrating days. Figure out where your filament path resistance comes from and eliminate it, then you should be good. For me it finally was the heatbreak and I replaced it, which solved it for me. Maybe your PTFE is not correctly seated, also happened to me. Or you're unlucky and have one or more spools of filament that just doesn't work (mostly due to varying diameters or density), which has also been reported by multiple users.
Don't care about the 1.9/2mm thing, I assume they tested standard heatbreaks (because why wouldn't they) and 2mm throughout and it didn't work. I don't bother why, but we know for a fact the setup works if you have intact parts and everything correctly assembled & dialed in.

Re: new mk2s MMU upgrade received for my mk2s

And also try my tips. Too long and fast retraction led to the wide tips on the filament ends at my printer. After reducing the retraction distance and speeds the filament tips look completely different, and I had not a single jam anymore. I think that’s also what Petr recommends, and it worked for me. That takes 10min to Test, as it’s just slicer settings.

Re: new mk2s MMU upgrade received for my mk2s

i didn't actually read all the pages from the blockage troubleshooting thread.
I'm actually printing the 8h hours benchy with 4 colors, 5 hours spent, all is ok.
So, even if the ptfe at id 1.9mm was intended, I actually prefer keep things working, I cross my fingers.
I've included the e3d specs, the diameter of melt chamber is 2mm, so when retracted, even if the 1.9mm force the diameter, while the filament is still melt, sometimes, it gets to 2mm and doesn't go back.
so why the id of 1.9mm ? Even with the steel tubes, same diameter.
Why not making everything to 2mm according to the e3d melt chamber diameter ?
I keep reading the thread, but I just still dont get it.

steph

Re: new mk2s MMU upgrade received for my mk2s

here are some news. benchy 4 colors 8 hours of printing, without any color changing problems.
see photograph.
in front, you have the original ptfe tube that I reduced 1mm because of difficulty to insert the multiplexer all the way.
before this reduction, color changing jams after 6-7 layers.
after the 1mm reduction, color jam after 1 layer.
I took a spool ptfe, without any chamfer, and adjust it to be ok after inserting normally into heatbreak, then the multiplexer is mounted normally.
and now, this MMU printer works like a charm.
believe me, for my case the ptfe with id of 1,9mm was the problem.
maybe some of you that still dont have a flawless printer like mine should try this option.
best regards, very happy with the results.

steph

Re: new mk2s MMU upgrade received for my mk2s

good weather on my mmu corrected mk2s.
I'm French so I've printed a frog.

and the frog's gonna take a bath.

believe me, if corrected, MMU just rocks.

I really think it's the adequation of heatbreak diameter with ptfe that causes problems. Mine is surely a 2mm, so the 1.9mm original tube was too tight.

just made a manual test this morning, put a pla filament manually inside ptfe then began to push to extract, then I've retired slowly it, the plastic at the extremity solidifies, and grows a little in diameter, surely because of self pla retraction. this makes about a 2mm diameter at the extremity of filament.
it surely cannot go back a 1.9mm ptfe tube.

Maybe, some e3d were built with 1.9mm as heatbreak, I cannot mesure mine, but now, this printer runs fine, I feel I'm surely luck, but would like to help others to correct their problems.

steph

Re: new mk2s MMU upgrade received for my mk2s

finally some big problems. now the filaments gets jammed inside the 1,9mm id steel tubes.
as told on other threads...
I will try with a lathe to machine them up to 2mm to see if this fixes the problem.
btw, mounting the multiplexer redesign to make a try.

very poor design, its not working at first. dont buy it !

Re: new mk2s MMU upgrade received for my mk2s

Before you kill your tubes, I suggest dissassembling the hotend and reassemble according to official e3d procedure. Clean or replace the nozzle if you have a spare. It is very important the heatbreak is properly seated against the PTFE. Mine wasn't, and maybe the same person assembled yours. If you find it is impossible to remove without violence (never good, it can easily be damaged), request a replacement.
Also try different filament if you haven't already, I cannot stress this enough. Two of my otherwise perfectly nice PLA brands were impossible to print and still are, even since my machine works.

Re: new mk2s MMU upgrade received for my mk2s

still same problem.
when printing is over, some pla filaments make a 2mm extremity wide, or during the print.
it wasn't passing thru ptfe, I've put a ptfe 2mm ID, 80% successful prints.
now, I've tried pla / formfutura pva, and the pla I've tried is pla+, seems to make more easily a 2mm bulb.
this 2mm bulb is the heatbreak diameter, I've already machined 1 steel tube to 2mm id, I'll make some further tests with the 2 other machined for the pva.
I've already mounted the ptfe id of 2mm the same way that the e3d site tells, I've just checked.

If I go little steps by little steps, I will dimension the all system big enough, so I should have more successful prints.
Otherwise, I will give up and sell the whole thing, like others did, I begin to be bored with this unreliable system.

thanks for your help Nils

steph

Re: new mk2s MMU upgrade received for my mk2s

to make a successful alien queen head printing, with pla / formfutura atlas support I've machined 2 steel tubes from 1.9mm to 2.0mm
seems to be a success now, I had a 8 hours continuous printing, almost finished at the time I did the photograph.
I finally dimensionned all around the max filament solidication size I've found : 2mm, seems to be the size of my heatbreak.
I've measured the heatbreak of my previous mk2s without mmu : 2mm.

I'll keep you informed, but it seems to be fixed.

steph

Re: new mk2s MMU upgrade received for my mk2s

Hi,
just 2 reports. With all to id 2.0mm, the mk2s with mmu works like a charm.
I did a lot more pla/pva and multicolor, and the extruder filaments change works fine.

I had a mail from Prusa today, they recognize that some heatbreaks were poorly assembled, I should have 1,9mm with the filaments blobx I had, and not 2mm.

So they will ship me a new multiplexer (I machined the steel tubes), a new e3d with correct heatbreak.

I'll report here when received and after doing the same tests I did before succeeding with the mmu.

PLEASE CONTINUE TO TRUST AND HELP PRUSA ! Like any other company, they are not perfect, and just try to improve their products.
The MMU system is unique, they need us, customers to help improve it, lke the mk3 surely, and they dont give up their customer.

Regards

steph

RE: new mk2s MMU upgrade received for my mk2s

Quick question?  Is the head break inside the hot end heat sink?  I saw a picture of the heat break on the website, but do not remember it during assembly.

  I am having filament tips retracting that are 2.0 mm diameter. I am getting filament stuck inside the ptfe tubes in my MMU2s and I am starting to understand Steph's thinking.  I would appreciate a quick answer.

RE: new mk2s MMU upgrade received for my mk2s

The heat break screws into both the heat sink and the heat block and, being made of stainless steel, helps to prevent heat transfer from the latter to the former.

The extruder provided by PR comes pre-assembled, so you may not have been aware of the individual components.

Peter