I somehow developed an enlargement of the nozzle diameter on both extruders. My right extruder was extruding out close to 1.0 mm diameter! Here are the damaged nozzles, and the new replacement 0.4mm nozzles.
Still not sure when/what happened. Might have been related to a head crash when my wife accidentally started the wrong job.
Looks like they have been scraping on an aluminum bed to many times.
Does your need have tracks in it? I’ve collided a couple of times and my need looks terrible but my nozzle was fine as aluminum is much softer than brass
I have a bed covered in thick kapton. No damage or scrapes are evident on the kapton.
Do you print abs or pla?
I print ABS and PLA the most. Some Nylon and HIPS too.
BTW, the big black coating was the result of a long nylon print job that went bad and was unnoticed for about an hour - the nylon had fully engulfed both nozzles, and 75% of the printing extruder’s hot-block. It was quite the sight.
@Joseph_Chiu , didn’t you try to level your nozzles by sanding the tips down to the same length at one point? This is exactly what I’d expect to see as a result of that.
Have you used solder, that will cause it to eat the nozzle
I did sand the nozzle a little bit a long time back ( @ThantiK , it’s all your fault! 
) – but I am pretty sure my nozzle orifice was not this wide.
It’s only more recently (about a week?) that I have started to see unusually wide extrusion from the nozzle and infill tearing that made me look more closely at the nozzle.
Perhaps sanding the nozzle had removed most of the material, and that there was only a thin bit of material left that somehow got removed. The mystery is why it looks so “clean”.
I had lately been playing around with KISSlicer and with adjusting my print bed elevation. I know there were a few prints where the nozzles were “riding the mogul” of over-extruded plastic before I got things dialed in. My guess is something during that process did the nozzles in.
From the looks of those nozzles, it looks like it was sanded more than a little. They’re perfectly flat and from the size of the annulus exposed, it makes sense that the hole was enlarged so much
If someone showed me these pictures, I would likely reach the same conclusion.
But the darn thing that I can’t explain is why this has become an issue only recently. I sanded the tips back around late March / early April, and I’ve been using the right extruder (top nozzle in the picture) the majority of the time since then.
The PLA and ABS cast-offs (from loading/purging) from at least about two weeks ago were not so abnormally large.
Then about two weeks or so ago (right around the time of the Reddit contest) after a filament change from PLA to ABS, I was getting a slightly fatter noodle than usual. Then two days ago, it was even fatter again.
So, I won’t deny that sanding may have contributed to this happening, but I’m fairly sure that the nozzle on the top was not this wide open until recently.
I’d say that the sanding shortening the narrow-bore portion may have weakened it and allowed the nozzle pressure to eventually push the metal out, widening the orifice, but that wouldn’t explain why the width of the annulus of the nozzle tip around the hole appears to be the same, which is what you would expect if it was purely a result of grinding the tips off of the nozzles
Well, it might be that with continued use, any irregularities were rubbed out? I was continuing to print – and since you’d expect the bore on the inside to be nice and round (but tapered), as long as it was rubbed flat, it would look nice and round?
One explanation, keebler elves
