MK2S started to show Ringing/Ghosting

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hendrik
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Joined: Fri Jun 16, 2017 8:04 am

MK2S started to show Ringing/Ghosting

Post by hendrik » Fri Jun 16, 2017 8:51 am

Hi,

This is my first post here and I starting with a problem :) Thanks Tom for the forum, I think it is an awesome idea!

I have a Prusa MK2S Kit for about 2 month now. Everything was fine (as far as I can tell) until I noticed some scratches on one Y and one Z rod and contacted support. The scratches are along the axis and seem to be caused by the bearings.

They asked me to remove the bearings from the rods and send them photos of the inside. When I put the Z bearing back 2 balls fall out. After I reassembled the printer and did all calibrations again I printed a 3D benchy. I used an existing gcode file that I had from an earlier print and I used the same filament (Prusa Silver).

I noticed that I had now a ringing on X and Y (the left hand benchy is an older print):

The door frame (parallel to X):
starboard_2.jpg
starboard_2.jpg (368.55 KiB) Viewed 2569 times
Below the back window (parallel to Y):
back_2.jpg
back_2.jpg (372.31 KiB) Viewed 2569 times
Since then this haunting me. I recheck many times the printer: every screw and nut and the belts.

Prusa sent me yesterday replacement bearings which are installed now, but the ghosting still exists.

I'm out of ideas.

What can cause such ghosting?
What would you check?

Any help is welcome! Thank you!

BR, Hendrik

PS: I'm still in contact with Prusa support, but I though this is a good place to ask for different opinions and maybe there is somebody out there with similar problems.

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brotherchris
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Re: MK2S started to show Ringing/Ghosting

Post by brotherchris » Fri Jun 16, 2017 3:42 pm

I have had some ringing issues lately. Let me print a benchy. We can compare and see if it's the same issue. I'll get back to you.

hendrik
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Joined: Fri Jun 16, 2017 8:04 am

Re: MK2S started to show Ringing/Ghosting

Post by hendrik » Fri Jun 16, 2017 5:12 pm

brotherchris wrote:
Fri Jun 16, 2017 3:42 pm
I have had some ringing issues lately. Let me print a benchy. We can compare and see if it's the same issue. I'll get back to you.
Thanks a lot!

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brotherchris
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Re: MK2S started to show Ringing/Ghosting

Post by brotherchris » Fri Jun 16, 2017 6:40 pm

So I printed mine facing the X axis. I am not seeing the same issues. I have seen it on other parts. Check out the green piece, the ringing is made worse by the structure of the part, it is only 2mm thick.

Image
Image


ImageImageImage

I do get belt ware on the X axis. It seems the bearing hold on the X idler is a little tight and causes belt rub. If you move the exturder all the way to the right by had you can feel the belt bind a little.
Image

I have ran into issue with the new U bolts. You can't over tighten or under tighten them. The manual says tighten until they touch the 45 degree turn. I have found that a little lose. The best method I have used it tighten them until the nut touches, then tighten then just until you can no longer move the U bolt back and forth with your fingers.

My guess is there is just a micro meter of slack in one of the U bolts. If you printed the benchy on the bed the same as I did, facing the X axis, any slop in the U bolts might cause this. I understand why Prusa went to the U bolts, but the zip ties were much easier to install, as tight as you can get a zip tie is exactly how tight it needed to be. Hope this helps.

hendrik
Posts: 22
Joined: Fri Jun 16, 2017 8:04 am

Re: MK2S started to show Ringing/Ghosting

Post by hendrik » Fri Jun 16, 2017 6:56 pm

brotherchris wrote:
Fri Jun 16, 2017 6:40 pm
So I printed mine facing the X axis. I am not seeing the same issues. I have seen it on other parts. Check out the green piece, the ringing is made worse by the structure of the part, it is only 2mm thick.
Thanks a lot anyway!
brotherchris wrote:
Fri Jun 16, 2017 6:40 pm
I do get belt ware on the X axis. It seems the bearing hold on the X idler is a little tight and causes belt rub. If you move the exturder all the way to the right by had you can feel the belt bind a little.
I have the same problem. The X carriage is misdesigned: The belt is hold 1mm to far to the front. I put the STL files in Fusion together to verify that.
brotherchris wrote:
Fri Jun 16, 2017 6:40 pm
I have ran into issue with the new U bolts. You can't over tighten or under tighten them. The manual says tighten until they touch the 45 degree turn. I have found that a little lose. The best method I have used it tighten them until the nut touches, then tighten then just until you can no longer move the U bolt back and forth with your fingers.

My guess is there is just a micro meter of slack in one of the U bolts. If you printed the benchy on the bed the same as I did, facing the X axis, any slop in the U bolts might cause this. I understand why Prusa went to the U bolts, but the zip ties were much easier to install, as tight as you can get a zip tie is exactly how tight it needed to be. Hope this helps.
Ok, thanks! I did the same. However Prusa told me that I might damage the bearings if I tighten them too much. So maybe I was too careful with applying any force when retighten them after I checked on the bearings. I will have a look!

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brotherchris
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Re: MK2S started to show Ringing/Ghosting

Post by brotherchris » Fri Jun 16, 2017 9:52 pm

Cool, let me know how it goes. I have tighten them to much before and it will mar the smooth runs very quickly. It is defiantly difficult to get them perfect. Do you know if/where there is an updated STL for the X idler piece I can print?

hendrik
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Joined: Fri Jun 16, 2017 8:04 am

Re: MK2S started to show Ringing/Ghosting

Post by hendrik » Fri Jun 16, 2017 10:24 pm

brotherchris wrote:
Fri Jun 16, 2017 9:52 pm
Cool, let me know how it goes. I have tighten them to much before and it will mar the smooth runs very quickly. It is defiantly difficult to get them perfect. Do you know if/where there is an updated STL for the X idler piece I can print?
I'm in the process, third round, no success so far ... :( Update will follow ...

I modified the openscad file myself and printed it in PETG. However I did not installed it yet, since I want to know first for sure that the ghosting is gone, or at least what exactly is causing it. The second reason is that it seems to me that the openscad/STL model takes in account some shrinkage of the material. My printed part won't hold the belt tight enough. if you are still interested, I can give you both files (openscad and STL).

BTW: In green part, the ghosting is in Z?

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brotherchris
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Re: MK2S started to show Ringing/Ghosting

Post by brotherchris » Fri Jun 16, 2017 11:02 pm

Yes in the Z, I guess it is probably more like Z wobble. What is your E steps set to? (M503) Is that the Prusa sliver filament you got with your kit? Mine is 161.30 by default and with the Prusa silver it under extrudes by about 5mm. Just a though, maybe there is a slight clog some where and the under extrusion is causing an issue. If you find the new value for your E steps use the m92 Exxx on your start G code and see if that helps.

hendrik
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Joined: Fri Jun 16, 2017 8:04 am

Re: MK2S started to show Ringing/Ghosting

Post by hendrik » Fri Jun 16, 2017 11:13 pm

It's now worse - I go to bed :(

Is there any infill? I noticed that the cubic infill can cause that. Try triangular or grid, or even add perimeters to have the wall filled up.

EDIT: Yes I have the same default steps for E. I printed with different filaments and the prusa is fine on my MK2 without changing the flow so far.

Tomorrow I will have another look at the Y carriage and see I can go back at least to the quality I had today in morning ;)

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brotherchris
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Re: MK2S started to show Ringing/Ghosting

Post by brotherchris » Sat Jun 17, 2017 1:22 am

Sorry to hear that, but I think you are on the right track. Is the printer setting on something different now maybe? Is it added vibration from the base?

No infill, the shell setting is high enough and the part is so thin it makes the walls solid.

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