Assembly and first prints troubleshooting - Prusa3D Forum

Firmware 3.0.4 doesn't seem to have a way to select type of filament I'm loading

idcstf — Sat, 11 Apr 2026 14:51:26 +0000

Hi All, I just updated my MMU3 firmware and it appears the Preload to MMU (advanced) setting has been removed. I am getting an Filament Does Not Match error from PrusaConnect. Anyone else having this problem? Is there a fix? Thanks Ahead, Ian

How to Pull Motor Shaft from Pulley?

Darth Bobo — Sun, 01 Mar 2026 21:06:49 +0000

I missed a square nut that is needed to secure a frame holder to the pulley body. I have removed all screws securing pulley motor to the body but the pulley at the end of the shaft will not allow me to pull the motor out. Any ideas of how to pull the shaft out of the pulley safely?

Feed Testing Error (Cutting?)

Pbovat2979 — Sun, 01 Mar 2026 16:37:48 +0000

I just got an MK4S with the MMU3, I assembled the MMU3 unit and now testing the feeds. I am trying to test slot 2 & 3 which is PETG (Clear) and PLA (Blue), respectively. It starts off good, however, after the MMU3 cuts the material I get a loading error. I pull out the material and the filament is square and not at a "point". I re-clip and make a point and again all works great until after the cutting feature. I assume this is where the problems is.

Does anyone know if there are directions on ensure it does this correct?

Maybe the blade is at the wrong angle or something?

FYI, the ABS (Black) slot 1 works just fine.

Any help would be great!!

Paul

MMU2S to MMU3 upgrade chimney base. Do I have to canabalize the old one for the brass insert?

Charon — Mon, 23 Feb 2026 04:52:10 +0000

I got the upgrade kit from Prusa a long while back and just getting to actually installing it. Was it supposed to come with an upgraded chimney base? The one I have from the MMU2 as shown in the attached photo does not match the upgrade manual.

Did I misplace the base? Or is it recommended to print a new base and extract the brass insert from this old chimney?

I have already completed the MK3S+ upgrade and been printing with it for a while, and am now trying to finish the MMU3 upgrade.

MMU, getting stuck in wipe tower, layer shift

mnentwig — Mon, 02 Feb 2026 16:36:20 +0000

(One possible failure mode. This isn't new information, just an example that shows it in isolation)

Filament may drip for whatever reasons (bad quality, too high temperature, possibly water content).

I ran into this in a five-color PETG print at max. recommended temperature. One of the colors (and, very clearly, only "green") started dripping three hours into the print. I had parked the head for tool change over an empty spot, and the resulting "blob" became very visible (usually it would be buried in the wipe tower, partly melting into it).

It's solid so it trapped the print head once it grew to Z height, causing the usual layer shift.

ad8413c1-20260202_172313.jpg

Newly installed MMU3, prints look good but crashes on wipe tower

Kyle Kerby — Fri, 30 Jan 2026 16:45:38 +0000

So I just got my MMU3 assembled and installed on my MK4S yesterday and so far on 2 test prints, it has printed the object just fine but the wipe tower looks like a mess with gaps and places with filament sticking up so the nozzle hits it. Those ones finished, but then we tried the 2 color Benchy and it didn't finish because of the wipe tower issues. The strange thing is that the object itself prints just fine. We're running Overture PETG with the test models Prusa has on Printables (obviously changing the filament type to be correct in the slicer because it seems like every multi color model and file is set for PLA). The photos show it really well but they're big so I had to zip them. Anyone have this issue in the past? I couldn't find anything with the search function so sorry if this has already been addressed and solved.

Filament loading issues and extruder clicking on MK4S Nextruder

Skynet — Fri, 30 Jan 2026 07:21:14 +0000

Problem description:"When loading the filament, it gets stuck between the two bearings. If I finally manage to get it through, there is a clicking sound as the filament skips on the geared drive (extruder). When I reverted back to the original parts from the MK4S, it started working normally again. Does anyone have any advice on what to do with this?"

Thanks

Filament Sensing Calibration failure on Core One

Ryan Elliott — Mon, 05 Jan 2026 01:55:04 +0000

Hi All,

Received a Core One for Xmas and just spent the last 2 days installing the MMU3 unit to it. Although frustrating, everything seemed to go according to the instructions until I reached the step to calibrate the filament again. I followed the steps and put a well cut piece of filament into the chimney on the extruder but it never detects the filament. I feel the filament get grabbed and the internal gears are pulling it in but it never passes calibration.

Would love some advice on what to do here.

Is the filament supposed to be "loose" in the MMU when not in nozzle?

glossyio — Fri, 02 Jan 2026 05:01:56 +0000

Still figuring out the MMU3 on Core One. My filament is _very easy_ to pull out from the MMU3 when it is not actively loaded to the nozzle. Is this supposed to be the case? It is like this regardless if it was was loaded into the nozzle and switched or if I just "pre-loaded MMU". The idler screws are just above the level of the idler body, as the handbook recommends.

I find myself accidentally pulling the other filament out of the MMU so it cannot automatically feed into it in next time. I bought the pre-assembled MMU3 (because the Core One Kit assembly was... an experience I didn't want to repeat), so I assume it was set up properly.

Thank you.

MMU3 / "Multiple Consecutive Filament Loading Errors"

David Holland — Thu, 01 Jan 2026 21:57:05 +0000

I've got the above message popping up on the screen, despite the print completing successfully.

I understand what it is and all, but I've never noticed anything like it occurring.

So, my question is, does the serial log spit something relevant out when it occurs? And/Or is there a way to reset the counter involved?

I've got octoprint, and am not above performing serial logging for the former.

Thanks,

David