Question regarding lead screw nuts
Hi together, i received my printer and Assembled it over the weekend. On the initial test i had an issue with z calibration, wont move. Then i did an bit of troubleshooting, it seems z axis Was blocked. I tried several Things, it ended up with loosing the need screw nuts just an little bit - so the nuts have an very small room to play, not even an half mm, but it is enough. After this all tests passed, the printer runs from sunday to now the third print with perfect quality. But - o think they should be tightened completely...... when i thighten the nuts z Blocks again. I am Sure, i build the printer correct, i take my time, and all fits nice, to problem with the core xy, no problem with belt Tension ( i printed my own Version of the belt tensioners with heat inserts, on this part the nuts are not the best way ) any Tips?
RE: Question regarding lead screw nuts
It is a known problem with the Core One design, and in particular with the kit building instructions, that the lateral position of the heatbed is over-constrained. The smooth vertical rods define the heatbed positions, and the black nuts on the lead screws have to "play along". But (unless they have been changed recently) Prusa's instructions let you install the nuts first, in some "random" lateral position -- and then jam in the smooth rods later. This may result in tensions in the Z drive.
But you do not have to leave the nuts loose. Move the heatbed all the way down, then tighten the six M3 mounting screws for the nuts. (Do not overtighten; the black nuts are POM plastic material.) As the heatbed moves up, the lead screws can tilt a bit, because the motors below are mounted on flex mounts.
This should give you a Z drive which moves all the way up and down without losing steps or blocking. If you get "groaning" noises during faster, longer Z moves, lightly lubricating the lead screws with the grease included in the kit should help.
RE: Question regarding lead screw nuts
Hi, thanks for your answer. Yes this i tried already - but as soon as i tighten the screws of the nuts it gets jammer again. And yes the leadscrews are already lubricated. Ok for now i will alles the nuts an bit room to play - it is really minimal, you cant even feel it when you try to lift the bed, because it prints simply perfect right now.
RE: Question regarding lead screw nuts
Should be alright as long as the screws don't shake loose over time. (Which would lead to an ill-defined vertical position and tilt of the bed.) But strange that you experience these stubborn issues.
When you remove the M3 screws entirely and rotate the nuts up and down the lead screws by hand -- does one of them feel much stiffer than the others? They should move without noticeable friction, but there seem to be some bad specimens out there: One user here reported a nut he could not even thread onto the lead screw. And when I contacted Prusa regarding a different Z-drive issue a couple of months ago, the support technician was initially pretty fixated on the idea of an ill-fitting nut. It should not be a problem to get replacement nuts if yours should not move smoothly.
RE: Question regarding lead screw nuts
In fact two of the nuts had an lot friction on intitial Installation. I never had this before on an lot printers i worked on in my 3d printing time. One Was Smoth and nice how i know this. But to be honest it is the first printer i habe wirh Plastic nuts, all other was Metal. And yes, if one gets loose, i will have to Rethink my actual way. I think then i go for heat inserts for the bottom part ( i wont destroy the original but redesign it and print it with heat inserts - and then use Loctite so i can fix the screws in this Position. But for now it is fine. Since sunday, 16 o clock Till now it runs without break ( except the breaks for empty the bed again ) with no issues. Maybe when i do this i go for Brassen lead nuts too.... but only if it makes problems. For now i have to see hiw stable the printer is over time - it has to beat for now the bambu x1cs, 4 of them already over 10k hours 🙂
RE: Question regarding lead screw nuts
I think there is a problem with a batch of lead screw nuts. A friend just built his C1 and was having the same issue with the Z. The lead screw nuts turned extremely hard, even by themselves, aka just the nut by itself on the lead screw.
He had some brand new spare lead screw nuts from his MK4, so he switched and they turned freely. All problems were gone.
Now he's fighting with Prusa to get replacements, but they are being stubborn, even though clearly the nuts were bad, since the new spare ones he had turned freely and fixed the issue.