Warped bed?
Hello everyone,
I've been noticing that, when printing any object, my bed is going up and down at every move (not Z hop or retraction). I ran the Z bed leveling calibration multiple times to make sure that the bed was as flat as possible, and also unplugged steppers and turned all three z-rods until everything was down all the way. Same thing.
Plugged it into octopi and ran it through bed visualizer and it's....not good.
Anyone else experiencing this?
RE:
It's because the steppers are not aligned when you run the Z calibration.
It's a design flaw ,you need to put spacers on the floor, on the top of stepper screws.
Prusa support says the printer compensate this, and in fact its true (put a large object, and you can notice the Z axis compensating this) , but not elegant.
In your case, seems to be the right front stepper it's missaligned, put a 1mm spacer on these stepper screws and run Z calibration.
RE: Warped bed?
Essentially the Z axes are referenced to the printer's base plate -- if the base is tilted vs. the CoreXY unit, so will be the heatbed. You can compensate for that with shims or spacers, as suggested by @jon-18.
But I find it strange that there would be a deviation of more than 1 mm. The base-to-CoreXY distance is defined by screw holes in the frame profiles and the back wall, and I found those sheet metal parts to be very precise when I built the kit, and with tight tolerances on the screw holes. Even with an unfortunate tolerance stackup, a 1 mm deviation seems excessive.
Anyway, it's probably not worth ripping the printer apart over this. Using spacers to shift the bed leveling vs. the base is the easier way out.
RE: Warped bed?
1mm is a lot. You can level it at the top by turning the Z axis stepper motor screws. Put something like credit card on the bed and turn the screws until it touches the nozzle. Should be enough to do it at the front corners and in the middle of the back. If you want to be extra precise, turn on load cell sensor on the screen and tune it accordingly.
RE: Warped bed?
I think one manner that prusa can "fix" this its Z leveling against the top position instead crashing the bed to the floor, using printed helpers with fixed distance.
1mm is a lot. You can level it at the top by turning the Z axis stepper motor screws. Put something like credit card on the bed and turn the screws until it touches the nozzle. Should be enough to do it at the front corners and in the middle of the back. If you want to be extra precise, turn on load cell sensor on the screen and tune it accordingly.
RE: Warped bed?
I think one manner that prusa can "fix" this its Z leveling against the top position instead crashing the bed to the floor, using printed helpers with fixed distance.
You mean, crashing the bed against the top plane instead -- using spacers below the CoreXY assembly? That might work, as long as the user puts all the spacers in their correct place before running the calibration. (But at least the printer could detect if that is not the case, by monitoring the load cell during the Z approach, so forgetting the spacers or placing them incorrectly should not result in damage to the printer.)
RE:
Don't forget that there is a single screw at the back of the chamber, attached to the middle of the bed assembly. That one can slide up and down a few mm. Loosen slightly all the screws along the outside of the printer that hold the core xy gantry assembly, and then loosen that middle screw. Don't unscrew them fully, you need them to be just loose so that the gantry falls down where it allows. Then tighten them all again. That middle screw at the back was holding my garntry slopped and when the printer was going from the front to the back, i could see the bed going down and then going up when it was coming at the front.
RE: Warped bed?
Don't forget that there is a single screw at the back of the chamber, attached to the middle of the bed assembly. That one can slide up and down a few mm. Loosen slightly all the screws along the outside of the printer that hold the core xy gantry assembly, and then loosen that middle screw.
Not sure I understand. Do you mean "there is a single screw at the back of the chamber, attached to the middle of the bed assembly CoreXY assembly"?
If so, it's not just that single screw which defines the CoreXY height in the back. There are also screws in the back left and right, which go directly through the frame's edge profiles. And those same edge profiles are also screwed to the chassis base plate. So the distance of the holes in these frame profiles define the distance between base plate and CoreXY assembly -- and in my experience from the kit build, they do that with pretty tight tolerances (because the holes are oversized by just a few 1/10 mm).
So I can't see where you found adjustment options which give you a few mm of play. Could you explain in more detail please? Thanks!
RE: Warped bed?
Yes, sorry i mean core xy. But when you assemble it, you first put that one screw at the back, that has a slot to go through instead of a hole. The other ones are threaded through the exosceleton pieces, but those are put way later in the assembly.
RE: Warped bed?
Yes, sorry i mean core xy. But when you assemble it, you first put that one screw at the back, that has a slot to go through instead of a hole. The other ones are threaded through the exosceleton pieces, but those are put way later in the assembly.
Yes, the assembly sequence is a bit strange, starting with the ill-defined hole in the center. I assume they put a slit in there because the height at which the back panel is mounted to the frame has some tolerance too (mounted with plastic rivets only).
But once you attach the CoreXY to the frame parts via the two outer holes in the back, those clearly define the height. You may have to loosen the center screw a bit to make all holes align and even be able to put the other screws in. I don't see how one can put everything together and end up with the CoreXY at a wrong height?