Printing problem, out of ideas 🙁  

Printing problem, out of ideas 🙁

Hello folk,

A few days ago, I was happily printing components for the latest thing I was doing. Then something ( a couple of things in fact ) went wrong, and now I'm really struggling to get back to where I was.

The first thing that went wrong was that, for the first time in ages, I paused a print for a few moments whilst the brim was still being printed, to deal with a small blob of plastic that had appeared. This might have been a warning sign, but I didn't realise it at the time. When I resumed the print, and returned a few minutes later, the extruder was making a strange noise, but it didn't register at the time. Shortly afterwards, it was clear that extrusion was not occuring, and I realised that the extruder was trying and failing to move the filament ( I had switched the filament sensor off, because I was printing fluorescent green PLA...) .

So I went through the nozzle unblocking procedure, poked the needle up the nozzle, reloaded filament, got filament flowing again, and could print.

Now the second problem happened. The filament 'locked' tight on the spool. But the printer just kept on going, trying to pull the filament off ( like I say, I'd disabled the filament sensor ). It actually managed to wear paint off the black metal frame by pulling a highly tensioned filament back and forth across it. I didn't catch this for several minutes. The fix was easy, just unload, chop off the damaged filament, free up the filament on the spool, and reload it.

However, ever since that point prints have not worked. 'Not worked' means problems with first layer adhesion and blobs of filament. I've tried a bunch of things :

1. First layer calibration. I've redone this several times, and I'm happy that this seems to work OK. Adhesion is not brilliant, but is sufficient. I can produce a perfect zigzag and a nice 'solid' block of print.

2. Playing with extrusion temperature. I've increased this, which leads to stringing problems ( as expected ), and decreased it, which leads to even worse adhesion problems. But I can't see any reason why I should need to change settings that were working fine only 24 hours before. 

3. Cleaning the nozzle. The nozzle seems to be more prone to getting stuff stuck to it than it was. I got rid of the build up, but this didn't solve the problem. Maybe a symptom not the cause.

4. Cleaning the 'Bondtech' filament grips. Well, I looked into the holes that show the gripping parts, and couldn't see anything to clean - the grips were nice shiney pieces of metal.

5. I've tried switching the filament sensor back on, this made no difference.

6. I've tried switching to 7 point auto levelling, but this did not help. I suspect it made things worse, because it takes longer to do, and whilst it's doing it the nozzle is hot and PLA is leaking out a little.

So I'm out of ideas. If this is a filament related issue, I don't understand why it has changed in the course of 24 hours. If it's a head positioning ( Z height ) problem, I don't understand why calibration works but prints don't. If it's a problem with the extruder or extrusion ( flow rate, whatever ), I don't know what it is.

Any ideas ?