Filament change during print dont work as expected and makes the printer crash.
 
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Filament change during print dont work as expected and makes the printer crash.  

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SveinHa
(@sveinha)
Active Member
Filament change during print dont work as expected and makes the printer crash.

Got my first Prusa (MK4 fw 5.1.3) up and running yesterday and on single color models, it works like a charm, vastly better quality and speed compared to my Ender 5 plus.

If I set up Prusa slicer (ver 2.7.4) with 2 virtual extruders and make a 2-color print, it all works fine until the filament change: Printer stops and ask for a filament change. I do as asked but when printing continues, the nextruder makes grinding noises and a couple of times it have grinded thru the filament and obviously are unable to feed more. Other times the printhead moves to the purge block but nothing comes out of the nozzle for the first second and then a lot comes out making bumps that the nozzle crashes into and get out of position...

A couple of purge block looks like this:

Anyone have an idea what is happening here?

I have a hunch that the newly inserted cold filament is too cold and therefore the nextruder is grinding the filament and when it becomes liquid, there come far too much out for a second or so...

Posted : 11/04/2024 9:38 pm
fuchsr
(@fuchsr)
Famed Member
RE: Filament change during print dont work as expected and makes the printer crash.

It certainly sounds like your diagnosis is correct but it's also not normal.

Can you please upload your project as a 3mf file, this way we can make sure it's not an issue with the settings. A 3mf file contains the model but most importantly also ALL your settings.

In PrusaSlicer, go to File/Save project as, to create the 3mf file. Zip-compress it to turn it into a .zip file (right-click Compress on Mac and Win11, right-click Send to/Compress on Win 10). Attach the zipped file a post on this forum using Attach file below the text edit box. It has to be a zip file, or the forum software will silently reject it. 

Posted : 12/04/2024 12:09 pm
SveinHa
(@sveinha)
Active Member
Topic starter answered:
RE: Filament change during print dont work as expected and makes the printer crash.

It went slightly different this time.

These are the only settings changed from default (I also set color for both virtual extruders but I guess that is just for visuals in slicer):

 

Downloaded file using PrusaConnect. Tried to start from printer display but ended in black screenand nothing more happend. Started the same file from PrusaConnect and it started as it should.

This time it went directly to the purge block without asking for new filament but still the same thing happend: The nextruder just started to grind the filament and nothing came out of the nozzle. This time I noted the extruder temperature and it was exactly 220 deg.C so my theory about cold filament is not correct (and this time, the temperature had been 220 for quite some time and a few cm of filament have been used). 

Since the nextruder was grinding the filament, I opened the door and, with the pliers, extracted the filament (which I was unable to get out the normal way). I broke off at the top, obviously, but the bottom end was quite unexpected:

Forgot about the tool change G-code so I added it now. Tool change G-code (copied from "Color change G-code"):

First layer temp was set to 230 deg.C but my eSUN PLA+ is speced to 205-225 deg.C so I changed first layer temp to 225 even as I don't think this is the problem (the nextruder starts grinding a long time after temp is at 220). Filament is brand new, purchased and opened yesterday. 

Next try: First color change left a large blob on the purge tower.

During next color change, I removed the purge tower to avoid collisions but same result:

Where do that large amount of filament come from? Is it possible that the filament loading run twice? Well... that may be possible since I did as I saw in an online video to just copy the color change G-code to the Tool change section and that G-code contains a purge... I'm quite certain that the G-code in the video was more that "M600". Anyway, the filament change procedure includes enough purging...

Ok, I changed color change and tool change G-code to only "M600" and did a new go but still no luck, major blob in the purge tower...

I need some help here. Attached is the latest slicer project. Nordnes nøkkelringer_V4.3mf

 

Posted : 12/04/2024 4:29 pm
SveinHa
(@sveinha)
Active Member
Topic starter answered:
RE: Filament change during print dont work as expected and makes the printer crash.

I also noted that ordinary filament changes using the printers menu always work well but filament change from slicer/G-code leaves a blob at the tip of the filament so it quite frequently won't exit the nextruder (as seen in one of the pictures in previous post).

Posted : 12/04/2024 4:35 pm
SveinHa
(@sveinha)
Active Member
Topic starter answered:
RE: Filament change during print dont work as expected and makes the printer crash.

I have seen in other threads here that Input Shaper may cause various problems so I tried without IS but that was more or less the same. This time I noticed that the large purge in the purge tower really is the nextruder running at high speed and seconds later the nozzle crashes in the blob and put the X-axis a few cm out of position:

Posted : 12/04/2024 10:05 pm
SveinHa
(@sveinha)
Active Member
Topic starter answered:
RE: Filament change during print dont work as expected and makes the printer crash.

I've done a few prints where I set filament change at a fixed layer in Prusa Slicer and that works like a charm... It is just two virtual extruders that mess things up... Any settings I've missed? Anyone who successfully have used virtual extruders and Multimaterial painting/Smart fill?

Posted : 14/04/2024 7:29 pm
ironfan72
(@ironfan72)
Trusted Member
RE:

I have virtual extruders set up for my Mk4 printers and use them to do same layer color changes. If the color changes are on separate layers I just use a single extruder profile.

Here's a thread with lots of information on single extruder (with virtual extruders) multicolor printing. 

https://forum.prusa3d.com/forum/prusaslicer/manual-multicolor/

The key for me was to add the correct tool change gcode and check the other recommended settings in the above thread.

{if layer_num >= 0}

local next_filament = filament_settings_id[next_extruder];

"M117 " + next_filament + "

";

M600 ; change to filament for extruder {next_extruder + 1}

{endif}

This post was modified 4 weeks ago by ironfan72
Posted : 20/04/2024 5:07 pm
Ckobar
(@ckobar)
Trusted Member
RE: Filament change during print dont work as expected and makes the printer crash.

funny, i tried that the other day too for the first time. And i got exact the same issues.

i searched the forum but nowhere did i find where and how do i add that code .

 i would be grateful if someone could explain that.  Thanks a lot.

 

the other thought. if the option of the "virtual" extruder is already included in the slicer. why do i have to add that code anyway. ?  And... if i have an MMU3, do i have to add code manual too ???

thanks for your help.

Posted : 22/04/2024 5:00 pm
SveinHa
(@sveinha)
Active Member
Topic starter answered:
RE: Filament change during print dont work as expected and makes the printer crash.

In Prusa Slicer: You need to be in "Expert" mode (upper right corner). Go to Printer Settings/Custom G-code and scroll down to "Tool change G-code" and click the pen/paper icon. In the right side of the pop-up, you can enter whatever G-code you want.

I have'nt had time to look more into it yet but color change at fixed layer height works nice and will do for now... I have ordered the MMU3 so I can wait a few weeks to get this running.

Posted : 22/04/2024 6:25 pm
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