Switch from PETG > PLA - weird blobs coming through after changing
Ok, I'm not at home to get a pic or video of what's happening, but I just want to get some thoughts on the issue.
Anyway, I somewhat frequently switch between PETG and PLA filaments. I have a roll of inland cleaning filament, and run a good amount through when changing from PETG to PLA (not necessarily from PLA to PETG), and run it until it doesn't appear to be pulling anything else through the nozzle. I am heating it to the same PETG temperature when trying to clear out the PETG with the cleaning (235 C, I believe).
After I'm done cleaning, I unload the cleaning filament, set preheat to PLA temps, and then load the PLA. The issue is here, when loading the PLA, it will start slowly pushing out a "sheath" of the PETG that was last used (usually my gray spool). As the PLA is going through the loading process, it'll build up a little bead of gray, then it'll come off down the stream, and then start building up another bead, and it keeps doing this for a while.
Last night, I kept loading my green PLA until I was reasonably comfortable that no more little gray bits were working themselves through the nozzle anymore. It seems fine afterward.
Any clue why the cleaning filament doesn't seem to be getting everything cleaned out? What else should I be doing when changing filament types?
Prusa i3 MK3 kit
MK3/S Upgrade Kit
FW 3.7.0
Slic3r PE 1.41.3
Re: Switch from PETG > PLA - weird blobs coming through after changing
You need a chemist to answer your question. My guess is there are probably properties of the PET that the Cleaning filament can't adhere to. Similar to why water washes off most contaminants best, and alcohol is used to catch other things the water doesn't touch. It sounds like a cold pull to clear the nozzle of your PET is a better choice than wasting cleaning filament.
Re: Switch from PETG > PLA - weird blobs coming through after changing
I swap between PETG and PLA all the time.
I just make sure I extrude a bit more filament than normal when the change is made.
Never had any issues nor have i ever used cleaning filament.
Re: Switch from PETG > PLA - weird blobs coming through after changing
[...] I am heating it to the same PETG temperature when trying to clear out the PETG with the cleaning (235 C, I believe).
I run my cleaning filament (eSun) through at 265C. The theory is that anything stuck got stuck at the normal print temp, so you want to be sure to go higher. The beauty of the cleaning filament is that it will extrude over a wide range of temps, so if any is left in the hotend, it will extrude easily at lower (PLA) temps, unlike PETG or other higher-temp materials.
You might try a cold pull. Try feeding some cleaning filament through, then resetting temps and letting it cool with the cleaning filament still loaded. Once cool, open the extruder screws, set print temp and begin pulling up gently on the cleaning filament while bracing the extruder with your free hand. At about 90C it should pop out and hopefully pull anything too big to extrude out with it. I do a cold pull whenever removing a nozzle.
Re: Switch from PETG > PLA - weird blobs coming through after changing
I swap between PETG and PLA all the time.
I just make sure I extrude a bit more filament than normal when the change is made.
Never had any issues nor have i ever used cleaning filament.
This has been my experience also.
Re: Switch from PETG > PLA - weird blobs coming through after changing
I swap between PETG and PLA all the time.
I just make sure I extrude a bit more filament than normal when the change is made.
Never had any issues nor have i ever used cleaning filament.
This has been my experience also.
Same. When it asks if the filament is the right color, I usually just say no once or twice.
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Re: Switch from PETG > PLA - weird blobs coming through after changing
I swap between PETG and PLA all the time.
I just make sure I extrude a bit more filament than normal when the change is made.
Never had any issues nor have i ever used cleaning filament.
This has been my experience also.
Same. When it asks if the filament is the right color, I usually just say no once or twice.
I usually say yes to the first question, but that is so I can jump in the menu to manually "move" the e axis so I can then apply about 3mm of retraction after purging my nozzle of the old filament before turning off the heater. But that is just me.
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Re: Switch from PETG > PLA - weird blobs coming through after changing
is your nozzle old? I have run allot of mmu 2 pla/petG prints and have not noticed the issue. I forget how much get put onto the wipe tower. maybe the wipe tower is enough to clear it.
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