I am shocked how that is even possible. Was printing fine one minute, then it started to fail with some stringing and when I tried to home it effectively destroyed the buildplate ..
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Even if the lead screw was stripped, it should still be turning as they are on the same belt.
Have you checked under the printer yet to see if anything is amiss on the Z belt assembly?
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Haven’t looked at the bottom yet. I mean when I say stripped I don’t mean the screw itself but that retaining nut or whatever that is. Just so random. Can’t even comprehend what could cause that.
The ball screw and nut are not going to strip out in anyone’s lifetime. If the assembly is overloaded it will wear faster, and backlash will increase, but to grind all the way through the threads would take a significant amount of force over a very prolonged operating interval. And all that removed material would have to go someplace. You’d see it.
I’m thinking busted belt.
The nut fits in to the build plate as a separate component. I bet it’s pulled out below the build plate, so the plate can move up and down even though the screw isn’t turning.
Be good to post one nice, high res image so it’d be easier to see what it looks like back there…
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When the belt breaks, doesnt the bed fall? I wonder if the belt has a bald spot.
I can’t tell if those are metal shavings around the screw. If so, the nut threads are probably gone.
The screw also either looks rusty, or like it got really hot. Based on the coloring of the metal. Did you happen to recently buy some cheap charcoal pellets? If so, they may be acidic
Looks like brass shavings. Sorry about that. Maybe the screw had a burr on it that ate the softer metal.
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If you get the chance, check those 2 screws and see if one or both have loosened, allowing the nut to lean over to one side and bind up.
They aren’t loose. Rock solid (according to wiki they are using red locktite so they will need some force to loosen)
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Oh and printer got 2000 hours on it. I’d say by now all burrs should have been gone if there were any.
It’s hard to be certain because of JPG compression when you zoom in. But if the nut was shredded, I’d expect to see a lot more brass. Especially, loaded in the grooves of the screw threads, since they’re what would have been grinding the threads off of the nut. And I would expect to see the screw threads chewed up a bit, too. Nothing looks awry that would explain why this area moves up/down when the screw isn’t even turning. That’s why I think the nut is actually further down on the screw. It’s not attached here, like it’s supposed to be. The screw not turning is a separate problem, maybe caused because the nut jammed the screw somehow.
Really, need to see under this part here.
Well support is sending me a whole leadscrew kit so will find out soon enough.
Definitely post some pictures of the defective assembly once you’ve removed it!
Will do. Not looking forward to the work. Seems to be quite a thing. Wonder what people do that aren’t technical inclined.
Yeah. The H2C is a mechanical marvel. Really impressive to watch it doing its thing. But I’m an engineer who’s been around the block a few times, and the thought of having to take it apart horrifies me. I don’t have a work surface large enough to spread all the parts out if I had to…
But I’m optimistic. My X1C ran perfectly for the 2+ years I owned it before I replaced it with the H2C. Hoping for a repeat. So far so good. 
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Obviously this is great. But what happens when someone isn’t technically minded and able to carry out the repair themselves?
I had the same thing happen to my H2D rear z axis lead screw nut, went completely smooth. Support sent me the lead screw kit and I replaced all 3, It wasn’t too terrible to do. I seem to recall seeing several other folks post the same so appears to be an issue.
Hey just wanted to chime in and join the dead rear Z screw H2D fan club!
In case this happens more often, may anyone with that issue try to find out what the root cause is? Maybe this could help several others by doing some additional regular maintenance steps. And maybe it will help yourself to prevent this happening the second time?
theres actually several of these issues on reddit as well. Looks to be a common issue and not a isolated one.