Right trapezoidal nut too tight
The right trapezoidal nut was so tight that it completely prevents the right Z-axis motor from working. At first I thought perhaps it was a bad motor or cable, but when I remove the trapezoidal nut the printer works fine (other than the right side hanging down a bit). So I'm sharing that in case it's useful to anyone else.
So I'd like to replace it. It's not a printed part, but I did find https://www.thingiverse.com/thing:2246502 which is for the Mk2. I figure I'd give it a shot (Nylon is cheap) but I'm not sure if the Mk2 and Mk3 are the same for this part. I'll know more tomorrow. Though I imagine a non-printed nut would be more reliable in the long run, I just got my Mk3 assembled, and I'd love to get it productive sooner rather than later.
Re: Right trapezoidal nut too tight
Lot of people have had this problem including myself, most likely it's not threaded properly.
Try the suggestions in this thread.
https://shop.prusa3d.com/forum/original-prusa-i3-mk3-f30/z-axis-failing-to-rise-with-mk3-build-kit-t13446.html#p59921
Re: Right trapezoidal nut too tight
If it is tight, then the nut is cross threaded. the nuts should actually feel pretty loose ( almost too loose ).
I would remove it carefully as to not damage it more, and try carefully re-threading it straight.
Ty Hoeffer
Palmyra, VA USA
Re: Right trapezoidal nut too tight
Both left and right nuts feel pretty tight putting them on initially. The left one loosened up as I threaded it down to the X-axis. The right took some effort. As far as I can tell neither is cross-threaded, as they're square to the rod, and when I remove them and look at the nut's threads they look clean. I removed and re-threaded the right nut a dozen times, including trying upside down in case the threads were in better shape on that end, and none of those tries felt dramatically looser, but the more I tried the gradually looser it got, and now I've run Z-calibration several more times, to the point where the printer is now somewhat working. That is, Z moves on the right moter are _usually_ working, getting better over time, and I am hoping that as the nut wears in it'll keep loosening up. Now I'm wondering if there was just a bit of plastic in the nut that's wearing down?
Ideally I'd replace the nut with a new one, to nail the issue down. But I can't imagine it's worth the cost of shipping from Prusa to the US just for my peace of mind. Does anyone know if this nut can be purchased from a US supplier?
Re: Right trapezoidal nut too tight
my z-axis trapezoid nut was very tight and i have no tool to thread it myself, but i found a tip for resolve this. I heat unscrew the top support of z-axis and i heat the endless rod with a torch. when the rod was really hot i screw my nut up and down. and its work. but be carefull to not disform too much the nut.