Y rods are not even after assembly  

Re: Y rods are not even after assembly

You can try my version of the holders if you want. I personally think technology needs to be past the zipties.
https://www.thingiverse.com/thing:2800776

Re: Y rods are not even after assembly

I've done exactly that. might be easier to sand out the bottom of one holder slightly.

Re: Y rods are not even after assembly

I've done exactly that. might be easier to sand out the bottom of one holder slightly.

Hi curtis

Did you also have this issue ?

What did you do to solve it ?
- Put stuff into the holders ?
- Or sand some of them out ?

I noticed that my idea of calculating the difference and putting pices in that elevate that does not work because also the other corners are then affected....

This frustrated me now because i just want to print stuff but with a bed that crooked it does not work.....

Thanks for any advice
Manuel

Re: Y rods are not even after assembly

Hi

I just want to check in to report, that i updated my mk2s to the mk3 and the new y rod holders are uneven. The left side is 0.6 to 0.8 mm to high up.

So be bed is so uneven that it can not corrected by bed level correction. I printed the y holders 2 times and switched all 8 trough on every corner so its not a missprint.

It happend on all the 4 y holders. My mk2s is very good tuned in but i think there is a general design problem.

So here are my questions:
1. Do you see also the problem ? (having an more uneven bed that mbl can solve and need to do some mechanical ajustments)
2. How to correct it ?

I cleaned the prints out of strings etc so this should be good but as i said i think the holes are a bit offset....

My idea of fixing this is to put a postcard piece (0.3mm) under the right side to clear this out. But i just wonder what other people do and what could be wrong with my printed y holders.

I can also see that the left y rod holder does not permit the y rod to go in that deep than the one on the right side. And as said, the print looks good. So i don't know whats up.

Also i dont want to go the full "put washers under all 9 points" i think i have to make it more even with the y rods first, beore i would attempt this. As you can see the bed itself is quite level, its just on one side much too high and on the other its to low...

https://ibb.co/iuv8b7

Thanks for ideas and pointers 🙂

Here are y rod holders that fit and do not need to be adjusted as they are designed to allow a slight spread when the rods are inserted https://www.thingiverse.com/thing:2793649/#files

Re: Y rods are not even after assembly

Here are y rod holders that fit and do not need to be adjusted as they are designed to allow a slight spread when the rods are inserted https://www.thingiverse.com/thing:2793649/#files

That may make it easier to insert/secure the rods, but there's still the possibility of the printed part itself being off OR the holes themselves being misaligned somehow OR some sort of user error OR a combination of the above. He's talking about an entire millimeter off. Zipties may look cheap but there's absolutely no way they're affecting you negatively.

What did you do to solve it ?
- Put stuff into the holders ?
- Or sand some of them out ?

well my blue tape measures .2 thick, so I'd start with that. But remember the tightness and alignment of the bearing u-bolts will also affect bed height.
While you have everything apart I'd check the dimensions of the holes themselves as well as the straightness of the rods.

Re: Y rods are not even after assembly

I don't know what has to be changed when updating an MK2s to an MK3, but you might consider that it is not the bed which is slanted, but the X axis, due to a misalignment of the mechanical end stops at Z max.

Re: Y rods are not even after assembly

That may make it easier to insert/secure the rods, but there's still the possibility of the printed part itself being off OR the holes themselves being misaligned somehow OR some sort of user error OR a combination of the above. He's talking about an entire millimeter off. Zipties may look cheap but there's absolutely no way they're affecting you negatively.

That's why i had the printed parts shipped from prusa directly to rule out print error. Still the error persists. You can even see that the rod on the left side does stick out more of the front left holder than in the front right holder. The holes on the plates seem misaligend somehow or more precise i think the screws are as the disance between the plates and the x extrusions does differ from left to right my ~0.2mm. So thats a start...

What did you do to solve it ?
- Put stuff into the holders ?
- Or sand some of them out ?

well my blue tape measures .2 thick, so I'd start with that. But remember the tightness and alignment of the bearing u-bolts will also affect bed height.
While you have everything apart I'd check the dimensions of the holes themselves as well as the straightness of the rods.
[/quote]

How will the tightness and alignment affect the height ? The bearings do not directly touch the bed as there are the distance pieces in between.
They are so tight, that the y rods will fall out very easy if held up vertical so i believe overtightenting is not an issue.

Thanks for cleaning that up

Re: Y rods are not even after assembly

I don't know what has to be changed when updating an MK2s to an MK3, but you might consider that it is not the bed which is slanted, but the X axis, due to a misalignment of the mechanical end stops at Z max.

Good point but the z top distance looks the same left and right also the x axis goes up in uniform i did check that.

Nevertheless: How would i spot such an error ? What can i do do further check that ?

Thanks
Manuel

Re: Y rods are not even after assembly

Nevertheless: How would i spot such an error ? What can i do do further check that ?

Ultimately, it is the angle between the x axis and the z axis which tells you whether it is the Y rods or Z max which causes the misalignment of the bed. In the end you want both, the x axis being parallel with the bed AND perpendicular to the z axis. But I would consider the potential error of the angle between x and z to be negligible anyway {atan(0.8mm/240mm)=0.2°}, so the question is rather if it is not just simpler to fix the issue by adjusting Z max instead of the Y rods or whatever.

Re: Y rods are not even after assembly

Nevertheless: How would i spot such an error ? What can i do do further check that ?

Ultimately, it is the angle between the x axis and the z axis which tells you whether it is the Y rods or Z max which causes the misalignment of the bed. In the end you want both, the x axis being parallel with the bed AND perpendicular to the z axis. But I would consider the potential error of the angle between x and z to be negligible anyway {atan(0.8mm/240mm)=0.2°}, so the question is rather if it is not just simpler to fix the issue by adjusting Z max instead of the Y rods or whatever.

How would i addjust Z on the left side ? Just not let the x carriage go so high ?

Re: Y rods are not even after assembly

Here are more pictures of the problem. Sadly prusa seems to have problems to show them in the post....

https://ibb.co/hLANkd
https://ibb.co/dE2rdy
https://ibb.co/dpehkd
https://ibb.co/dUm6BJ
https://ibb.co/m766BJ

Hope this helps to give some pointers.

I will have time to tinker with this on monday so then i can try your suggestions 🙂

Re: Y rods are not even after assembly

In those pictures you can clearly see the "elephant foot" on the printed y-holders. Have you tried making sure they are trimmed flush with the rest of the part?

Re: Y rods are not even after assembly

In those pictures you can clearly see the "elephant foot" on the printed y-holders. Have you tried making sure they are trimmed flush with the rest of the part?

Uhh i did completly miss those. Funny because there are the orginal y holders prusa send me... I will work on those and report back. However i previously printed them myself and i took great care to make them flush on every side so i doubt it will make a difference...

Re: Y rods are not even after assembly

How would i addjust Z on the left side ? Just not let the x carriage go so high ?

Wasn't the left side which is too high up? In that case Zmax on the right side must be lower.
You also can try adjusting the aluminum profiles and the front and backplates - any mechanical connection between the Y rods and the X rods can contribute to an apparently slanted bed, on both sides. So there are a lot of possibilities, but nothing wrong with just counteracting a misalignment at the most convenient spot instead of wasting time on finding and fixing the root cause (IMHO).
On the other hand, the firmware mesh leveling should be able of taking care of this. But since I switched from Prusa-Marlin to the original Marlin, I cannot tell if or why Prusa-Marlin would have problems with it. I used Prusa-Marlin only for a short time, but back then it never complained about the misalignment of 1mm my bed has - but I also never checked whether bed leveling actually worked. I assume it did, because the purge line looked good and printing at the center worked fine, which couldn't be the case if there was a considerable residual Z error. So I am actually wondering why you cannot print, at least anything that has been sliced with some default MK3 slicer profiles. Note that there is some magic in the start G-code sequence that is likely necessary for bed leveling to work correctly.