Long thin strand of filament after unloading  

RE: Long thin strand of filament after unloading

No.  I am not sure why either would cause this unless 4.21 changes retraction.  

RE: Long thin strand of filament after unloading

Posted by: @tracy

I've recently started getting a long thin strand of filament after unloading. It reaches from the tip of the filament all the way to the hotend and is thin as hair. I recently upgraded to 4.2.1 and replaced my hotend PTFE tube so I'm not sure which, if either, is causing this.

Has anyone else experienced this?

I think that nothing has been changed regarding the unloading routine in 4.2.1 (only BSOD - bluescreen issue).

https://github.com/prusa3d/Prusa-Firmware-Buddy/releases

It is more likely that something went wrong when installing the PTFE tube. The length of the PTFE piece in the hotend must be properly adjusted and must not have any unclean passages (gaps).

RE: Long thin strand of filament after unloading

Posted by: @tracy

I've recently started getting a long thin strand of filament after unloading. It reaches from the tip of the filament all the way to the hotend and is thin as hair. 

Mine does this as well.  I don't think it's a firmware issue.  I replaced the ptfe tube in the hotend and adjusted the heatbreak but it didn't change anything, but I'm also suffering from really poor print quality so it seems like there's definitely something wrong.  Let me know if you find a fix.

RE: Long thin strand of filament after unloading

I do not have the Mini, but I've noticed this off and on with the I3.  It seems to occur with no particular cause or pattern.  I just pull it out, break it off, and toss it in the plastic scrap box.

RE: Long thin strand of filament after unloading

That's pretty common. I get that yjsy my Mk3 and Sidewinder printers. It varies depending on what filament is loaded, how hot it is when unloaded, how quickly or slowly I pull the filament out of the extruder, how much moisture the filament has absorbed and any number of other environmental variables. Some snaps off cleanly after a few inches, but some will let me draw out fine wisps for yards if I go slowly. I wouldn't worry about it too much. I stuff the strands in a little box and hit it with a heat gun to avoid having them float around the house. Get a bit under your shirt or in the sheets and it'll drive you nuts.

RE: Long thin strand of filament after unloading

If this is what I think it is, I change my answer - I have seen it also.  Can you post a photo?

RE: Long thin strand of filament after unloading

@cwbullet

The thin part is almost 16" long. It's thinner than a hair. This end was attached to the filament before I trimmed the end.

RE: Long thin strand of filament after unloading

While I can't be 100% sure, my cause of "stringing" with PLA+ was the filament absorbing too much moisture. I've since bought a bunch of 50g silica gel packets, and store my filament in ziplock plastic bags with 150g silca gel per 1kg filament reel. After a couple of weeks storage, the stringing is gone, and I haven't changed anything else. Top matches googling for "3d printing stringing" seem to mention moisture, along with temperature & retraction as common causes.

RE: Long thin strand of filament after unloading

I get this thin strings of filament nearly every time PETG is unloaded - also on my MK3S. Never has any problems with it.

RE: Long thin strand of filament after unloading

@area51

Same here.  

RE: Long thin strand of filament after unloading

I am experiencing the exact same issue after replacing the hotend PFTE-tube. I got back the very good print quality but I have this stringing while unloading the filament. I am thinking that the full turn (360 degrees) release on the lower fitting of the heat sink after pre-stressing the PFTE-tube is a bit too much and might cause this issue. On the next maintenance I will try with 3/4 of a full turn (270 degrees) and see what happens.

It looks like the PFTE-tube installation is a very sensitive factor which affects both print quality and other common issues of the MINI (clogs, stress on the extruder, z-banding, etc..).

RE: Long thin strand of filament after unloading

I came to the conclusion this is caused by wet filament. I bought a food dehydrator and have been good about using it. I no longer have this issue.