Problem is, just when I was supposed to find a clog, I found nothing. Only TONS of brownish powder (which I believe is the normal product of printing).
So, where next? What I should look at to solve whatever it is that looks to the printer as a clog but it is not such?
I’d try to print again and if it still appears to be clogged, i’d try a cold pull of the nozzle.
The extruder does need to be cleaned some times. The brownish powder could possibly let the extruder gears slip and in that way appear clogged, but in fact it just is not able to pull on the filament.
The brownish color is the bearing, which it seems might have needed some oil when the bearing was made. But it’s dry and that brown stuff is rust I suspect.
The drive gear might be worn so that it slips. You didn’t post pictures of your extruder assembly so this is a guess.
If there’s no obvious mechanical problem with the drive gear assembly, the problem may be a bad stepper motor. I’ve seen a couple of posts from people who’ve had that problem.
And make sure the spring tension thingy that holds the filament drive wheels together is screwed down tight. I suppose it might be possible for it to back out over time…
Thanks, insightful stuff. When I get back to the printer this week, I’ll send pictures of the pieces: the gears are obviously ground down, specially on their edges. Thanks you both for your replies.
OK, finally back to my printer, here go some pics from my disassembly of the extruder unit. Really hard to tell from the pictures, and also because I brushed away most of it, but the whole thingy is covered with very thin brown powder (like brown flour).
I ordered a new extruder unit, which arrived already, so I think I will just replace this one and keep it as emergency spare.
I would not be surprised if even after replacing it, the extruder is reported to be clogged any way.
Another detail I forgot to add: I had a .8 nozzle on. I will try with it and a .4 as well to discard a malfunction on the nozzle as well.
Thanks again, @MariusB and @RocketSled
Oil the bearings with some lightweight oil (not WD40) before you put it all back together and I bet the next time you take it apart there won’t be any of that brown (iron oxide) powder.
Make sure the nozzle isn’t clogged at the top. To check this, you’ll need to remove the nozzle. Where the filament enters the nozzle, there shouldn’t be any blobs. If there are, you’ll need to soften it a bit and pull it out. The filament won’t soften at the top when the printer heats up the nozzle, so new filament can’t be pushed in. I use a soldering iron for this. Heat the tip to around 200°C and carefully push it into the filament blob, then I can grab it with a small pair of pliers and pull it out.
In my case, the lump sometimes looked different, it was right on top (thanks for the picture), which also caused problems when cutting the filament during filament changes. That’s why I built myself an upgrade. Maybe one of them will help you permanently, like it did for me.
A slightly more complicated version, ready for extensions:
after replacing the extruder, got the same message. So, I replaced the extruder unit with a brand new one, SAME MESSAGE.