Z-Axis Alignment
Just finished my upgrade from MK2 to MK3 and noticed a problem that I never encountered on the MK2.
Whenever I cut power or reset the printer and the z-axis motors lose power the left side drops down 2-3 mm. This forces me to re-run the Z Calibration to get it level again since you can no longer force the z axis beyond the preset 210 limit with the lcd wheel.
Has anyone else experienced this? If so, what did you do to correct the problem? I'm thinking about replacing the trapezoidal nuts with ant-backlash ones to see if it fixes the issue.
Re: Z-Axis Alignment
Seems like I am the only one with this issue. Guess it's time to order the anti-backlash nuts to see if they help the situation.
Re: Z-Axis Alignment
IMHO anti-backlash nuts don't help on the Z axis as the weight of the x gantry permanently pushes down the lead screw nuts.
They work in systems with x/y lead screws.
Cheers Pete
Re: Z-Axis Alignment
I had the same issue with mine. I found that the trapezoidal nut on the drooping side was a significantly looser fit on the leadscrew than the other nut. The root of the problem, IMO, is that these leadscrews use a 4 start thread - the thread pitch is just too coarse for the unpowered motors to resist the weight of the X gantry without a little help.
I won't necessarily suggest you do the same, but I ended up roughing up the very end of the threads of the problematic trapezoidal nut, just enough to add about as much friction as the other nut. If you try the same, I'd suggest doing it in tiny steps, testing the fit at each step.
Re: Z-Axis Alignment
I won't necessarily suggest you do the same, but I ended up roughing up the very end of the threads of the problematic trapezoidal nut, just enough to add about as much friction as the other nut. If you try the same, I'd suggest doing it in tiny steps, testing the fit at each step.
Interesting approach. I will first try swapping them with each other and see if it is just the one. If the problem persists I will try roughing it up a bit.
Trying to find just regular T8 trapezoidal nuts with the same mounting hole alignment and top diameter is a challenge.
Re: Z-Axis Alignment
Hi Richard
Did you try swapping the nuts around to see if that helps?
I know on my Mk3, I do have to push quite hard to make the Z axis move.
Peter
P.s. You could try offsetting the nut with a small piece of paper (or a washer) under one side
Please note: I do not have any affiliation with Prusa Research. Any advices given are offered in good faith. It is your responsibility to ensure that by following my advice you do not suffer or cause injury, damage…
Re: Z-Axis Alignment
Hi Richard
Did you try swapping the nuts around to see if that helps?
I know on my Mk3, I do have to push quite hard to make the Z axis move.
Peter
P.s. You could try offsetting the nut with a small piece of paper (or a washer) under one side
That's tonights mission. Swapping should tell me what I need to know.
I'm not sure about offsetting. It only loses level when the power is removed. This is normally not an issue as my printer never gets the power switch turned off, but if there is a prolonged power outage or as in this case I need to move it after assembly, it creates the problem.
Re: Z-Axis Alignment
Trying to find just regular T8 trapezoidal nuts with the same mounting hole alignment and top diameter is a challenge.
Just keep in mind that these are 4 start leadscrews - regular 1 start nuts won't fit.
I'm curious if swapping the nuts helps. It didn't for me, but that doesn't mean a lot since quality control led us here in the first place.
Re: Z-Axis Alignment
PJR's thought about offsetting, or tilting the lead screw nut with a piece of paper, will marginally increase the friction, which may be enough to correct the issue.
you could also consider getting replacement nuts in the hopes of finding a closer fitting nut
Good luck, Joan
I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK
Re: Z-Axis Alignment
PJR's thought about offsetting, or tilting the lead screw nut with a piece of paper, will marginally increase the friction, which may be enough to correct the issue.
you could also consider getting replacement nuts in the hopes of finding a closer fitting nut
Good luck, Joan
Well, I placed a small paper wedge under the problem nut and it mostly works. I was wrong in my initial estimate of the drop, it was actually 4mm. After placing the paper wedge (5 printer paper sheets thick) the drop is down to 1mm. If I place 1 additional sheet thickness it stalls the z-axis on that side when trying to rise.
In other words, better but still not what I was hoping for. Trying to find the exact replacement trapezoidal nuts is almost impossible without contacting Prusa and paying a fortune for shipping.
Re: Z-Axis Alignment
I am having the exact same issue as you described after doing an Mk2.5 upgrade and "Bear" frame. Going to try offsetting the lead screw a bit based off suggestions here, but has anyone found a good source to replace the lead screws aside from shipping direct from Prusa?