MMU3/MK4 Wipe tower issues(too much purged)  

RE: MMU3/MK4 Wipe tower issues(too much purged)

I am also having this issue with my mk4 with mmu3. Changing the value within prusa slicer does not seem to actually change it at all either.

RE: MMU3/MK4 Wipe tower issues(too much purged)

Are you both using the full Prusa Mk4 MMU Upgrade, or are you using non prusa upgrades?  are you using the latest firmware for the Printer and MMU?
do you have pictures of the Nextruder from the front please?  
regards Joan

RE:

Hello Joan

Yes, i'm using the full Mk4 MMU3 upgrade. Yes, both device is on the latest firmware.For me it seems the issue is with the Sunlu PLA+ material itself. It gets way to liquidy and leaves huge blobs on the wipe towers.Tried to tighten/loosen up the screws on top(with springs) of the nextruder, but it had zero effect with my Sunlu PLA+.I have no issues with Prusament PLA or PETG. Especially flawless with PETG. It makes beautiful tips, so it can slide very easily.

RE:

All original prusa here. Just got the mmu3 in the mail about an week ago. Have had the mk4 for about a year. Attached pictures to show full setup.

My best guess to the cause of the issue is specific to when a filament change occurs on the wipe tower by purging to create the conic tip with the filament end. And that method is impressive that it does not have a stringing end. However, that ordeal does seem to be fixed and separate from any adjustable setting with the slicer or on the panel itself.

Essentially it makes a wide/rapid wipe, and does not always anchor where it is supposed to go creating a bugger. The bugger gets wiped off usually, but it of course hardens and it is just a matter of a pass or two before it becomes a collision with the nozzle itself. And these collisions are not minor. Impact hard enough to flex the heat bed and sometimes shift the sheet itself.

RE: MMU3/MK4 Wipe tower issues(too much purged)

And yes, fully up to date on firmware and software/slicer. Last updated yesterday before starting the green/purple/white halved ball print that is pictured. 

A careful eye can see the beginning of a filament bugger on the wipe tower and shift in the print itself from a past collision and noticeable that I manually corrected it after a few layer passes. These issues stem from the tower’s bugger blobs. 

RE: MMU3/MK4 Wipe tower issues(too much purged)

Hi @wcrwcrwcr

not sure what is causing your collisions, is this happening every model?  

regards Joan

RE: MMU3/MK4 Wipe tower issues(too much purged)

Hi @markG
the tension springs and screws on the Nextruder, are predominantly responsible for  ensuring satisfactory operation of the filament sensor The tips of the screws should be just showing at the end of the filament sensor arm, 
Looking at yours they look OK. If you screw them in too far, you get too much tension and can damage the filament in the extruder. 
the liquidy status of the filament, suggests that the filament is too hot, it's possible that the blob is due to the excessively liquidy filament is getting pumped out of the nozzle instead of being re formed into neat ends during the 'Ramming' period before a filament is unloaded from the extruder causing unexpected blobs.

what do your filament tips look like using Sunlu, when unloaded to the extruder? are they stringy? or neat and tidy

Could you try a lower nozzle temperature

PLA MMU3print, Purge blocks seem to be more widely spaced than PETG Purge blocks, perhaps this is to allow the strands to cool more quickly 
The print above is a mix of Prusament and other filaments.

RE: MMU3/MK4 Wipe tower issues(too much purged)

Yes, that was my idea first, that the tension is too strong and maybe it grinds on the filament, so i loosened a bit, but it had no effect.
I  started to lower the temp by 5°C every print. I'm at 205°C now.

When pulling out the Sunlu PLA+ filament, one of two thing usually happens.
1. It leaves a 1-5cm thin string at the end.
2. It it stretches the filament by a half a centimeter, so the last 2 cm of the filament has a thinner part in the middle, but when it pulls out, there is a string at the end, but this time it's way longer string.
The most annoying thing is, it's not consistent, it happens randomly while printing, so it's even harder to track down the problem.

I pulled out 2 Sunlu PLA+ from the MMU3 now, the tips looks like this. This is how it looks after a 205°C print.
Tried to print at 200°C, mostly same result as on 205°C.
At 195°C, it gets even worse. More stringing at the tips, now very thin but long 5-7cm and the print paused 2 times because of "clogged nozzle", but it wasnt clogged.

I use the ObXidian nozzle. Could that have an impact on this issue?

RE:

So, it was a busy day.

Someone on Reddit told me, i should check my slicer settings, especially the Filament -> Toolchange parameters.
Well, all the values there were wrong...
Created new Filament profiles from the Generic PLA and now it works flawlessly.
It wasn't the material, it wasn't the hardware, it was purely the slicer and me, because i used an old profile.
All the filament tips are now perfect 10/10. No blobs, no weird behavior, no stringy tips.

RE: MMU3/MK4 Wipe tower issues(too much purged)

Excellent  news

Joan

RE: MMU3/MK4 Wipe tower issues(too much purged)

As I have the exact same proble, with my freshly built MMU3 Upgrade: What are the correct values?

RE: MMU3/MK4 Wipe tower issues(too much purged)

Hey. I deleted all the profiles i had before and only use the new ones, created from Generic profiles.

RE:

The issue seems simple to me...

The nozzle parks directly over the purge block during MMU filament change instead of somewhere safely off to the side.

If there is a problem with the reload, sometimes hot gooey molten plastic piles up on top of the tower and becomes an obstacle for a fast moving nozzle. 

If it were to pause safely off to the side of the tower during filament change, then the erroneously ejected ooze would fall harmlessly on the bed.

Done.

I don't know how open the PrusaSlicer people are to making a change or adding an option like this.

RE: MMU3/MK4 Wipe tower issues(too much purged)

another option would be for the slicer to design a spill hole within the wipe tower over which to park during filament changes. That would allow an area for unexpected extrusions to collect and not leave a collision hazards on the tower. I imagine this to be like a little waste bin in the tower.

RE: MMU3/MK4 Wipe tower issues(too much purged)

I am also having this issue with my new MMU3. I'm using all Prusa everything and I am having issues with the printer over-purging on the wipe tower, making a big bump, and then getting caught on that bump a few minutes later. It eventually either rips off the wipe tower, causes a layer shift, or both. I haven't been able to complete a single MMU print 🙁

Posted by: @markg-2

Hello everyone!
I need some help.

So i built the MMU3 for my MK4. But i have problems with the Wipe tower.
At some points while wiping, there are these thicker purge lines.
But i have 2 issues with those lines. It seems it's extruding too much when purging at some points, which causes both issues while printing.
1. It's causing serious layer shifting issues. When finishing the purge, the other already cold purged line blocking the path of the nozzle, which causing the printer to skip and shifting the layers.
2. The extruder cannot push the filament out, because these lines will block the nozzle, causing the print to pause and promts a requeyt for checking the extruder.

Is there any way i can disable in the slicer the extra purge and just have longer thinner purge lines?

RE: MMU3/MK4 Wipe tower issues(too much purged)

Thank you. I had the same issue and this was also the cause and solution. Forums FTW!

RE: MMU3/MK4 Wipe tower issues(too much purged)

Had the same issue, here.. wound up not only creating a new profile, but also reduced by temps by 10 degrees or so, primarily because I'd read a number of folks on Reddit talking about how Polymaker's polyterra tends to print better with lower temps.

Test sheep came out fine, afterwards (minus the fact I didn't get the 2 color purges long enough to stop color bleed), and then printed the 2/3/5 color rings to make sure everything was working right.  (had one issue of filament binding, because I had the ptfe clip a bit too close to the MMU3, so it had a slight pinch, in that spot)

RE: MMU3/MK4 Wipe tower issues(too much purged)

I have the same problem, but it keeps the same, even after adapting the values for MMU3 at the filament profiles... I have crashes with the wipe-tower with the nozzle causes x or y-shiftings, see pictures

RE: MMU3/MK4 Wipe tower issues(too much purged)

Dear all,

I think I found a solution for this whole topic. To be honest - not me, but Sebastian R. of the Prusa Support (Transcript of Thursday, June 20, 2024, 09_28_03 pm. Operator_ Sebastian R.. Visitor_ Dennis)

First try results to a swipe-tower like this:

Blue and Green indicates the shifts in X and Y-direction due to collision. In red indication shows the "too much purged" material, which causes to a collision with the nozzle. 

First improvement: Set your Filament to standard condition for multi-material, basically this data (see posts above, same feedback)

It was getting better, but not perfect:

Same problem: To much purged material and collision again. The key-point was to set the temperature of all PLAs to the same level..

The test print and the print of my project results to this:

Problem solved!