Anyone ever had Z-banding issues?

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Michael Giuliani
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Anyone ever had Z-banding issues?

Post by Michael Giuliani » Thu Mar 01, 2018 6:43 pm

I just went through over twenty emails with Lulzbot support and we couldn't figure out what on Earth was wrong with my printer. I've got z banding going on that isn't coming from an unleveled or bound up X carriage, the motor shaft isn't sheared or broken, all motor wires look fine, the couplers look fine, the threaded rods aren't bent, my belts are taut, and nothing else on the Rambo looks damaged. The models and slicer don't have any affect on the banding, good or bad. Here's a video of what my left motor is doing (that seems to be the culprit but I don't know for sure now after all the emails): https://www.youtube.com/watch?v=U0tLE2m3qDE. Any community suggestions?

ScottW
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Joined: Thu Dec 10, 2015 1:00 pm

Re: Anyone ever had Z-banding issues?

Post by ScottW » Mon Mar 05, 2018 8:37 pm

The coupler oscillating as the toolhead moves to different areas of the bed is a normal result of the bed level compensation. There are some noises I can’t identify from that video; it would be helpful to see a wider video showing what movements are occurring when each sound produced.

Can you post a photo of a part that displays the issue? If you print a cube, is the banding the same n all sides?

Rhoderman
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Joined: Fri Dec 18, 2015 7:10 pm
Location: CO

Re: Anyone ever had Z-banding issues?

Post by Rhoderman » Fri Mar 16, 2018 8:24 pm

I had the same, VERY same I must say, problem with my machine. It all happened after I put in the vibe dampener for the Y-axis. Everything was so quiet, I noticed all the different noises that were always there, but not heard. My complaint to Lulzbot was never resolved by them. I did eventually discover what was causing it though. My Z axis motors weren't in phase, causing the bed to be tilted. The software actually compensates for that by moving the Z as it traverses across X or Y. That's the shaft movement you show in your video, and what you're hearing as "ticka-ticka-ticka" at various frequencies that don't make sense at first.

Your problem is that your Z axis motors are not "in sync" with each other. There are two motors that are given the same drive pulses, but if one stalls and misses/ignores pulses, and the other one moves, they aren't in time with one another any more. The Lulzbot Mini can compensate for this by creating a virtual plane that the Z motors can "track out" by moving while it prints. However, if your two sides are off far enough, you will hear those thunk-thunk-thunk noises you describe.

While normal to an extent, if your motors are way off, you will probably see and hear a lot more of it.

Please do this:
Do a normal start in Cura.
Note what it displays as it taps all four corners.
Those numbers should be close, within say 0.2mm, and even less is even better.
What are your numbers?? Please post what you have before and after you change it.
Those numbers are what I watch each and every time my Mini initializes before a print. If they're way off, I abort, figure out why, and retry.

Press the "motors off" button in Cura. With "motors off" you can manually move either Z axis motor/shaft with your fingertips. Try a quarter turn in either direction, make a note of what you did, then re-run the print and note what happens. If the results change in the right direction, continue. Wrong direction, go the other way. Too far, go back a little.

As a side note, it could also be front to back (Y) movement or tilt. If you have that, we'll figure out how to fix it then.

Here's what I just ran tonight and it prints pretty evenly with little Z motor movement.
mini ini.png
Jim
Lulzbot Mini

GeorgeKuzyk
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Joined: Sat Apr 04, 2015 7:42 pm

Re: Anyone ever had Z-banding issues?

Post by GeorgeKuzyk » Sun Apr 01, 2018 7:50 pm

I have the same issues now and will try what you have here. Only problem I am using Cura 2.6.69 and do not have a way of seeing the leveling info taking place. Not that I know of. I liked the Cura that you are displaying here on the forum. Will update here if it helped. Thanks

Galadriel
Aleph Objects | LulzBot
Posts: 279
Joined: Mon Sep 25, 2017 10:23 am

Re: Anyone ever had Z-banding issues?

Post by Galadriel » Mon Apr 02, 2018 1:06 am

GeorgeKuzyk wrote:
Sun Apr 01, 2018 7:50 pm
Only problem I am using Cura 2.6.69 and do not have a way of seeing the leveling info taking place. Not that I know of.
You can still view that information if you open the "Console" after you start your print/autoleveling sequence. It is right next to your connect and disconnect buttons in Cura.

mikehill85
Posts: 23
Joined: Wed May 24, 2017 6:31 pm

Re: Anyone ever had Z-banding issues?

Post by mikehill85 » Mon Apr 08, 2019 8:47 am

I also have this problem and haven’t been able to sort it out. I even tried swapping my lead screws to see if the side the problem was on changed. It didn’t. I did find a crack in my motor mount on the side closest to the board. This might be the culprit but damn if I want to remove the board and rewire everything to remove it. Also, this might just be an almost unavoidable consequence of the use of lead screws and something we can’t do much about.

Keebie81
Posts: 114
Joined: Sat Dec 20, 2014 12:53 pm

Re: Anyone ever had Z-banding issues?

Post by Keebie81 » Tue Apr 09, 2019 7:34 am

Also try removing the bearings at the top of threaded rod. See if that helps.

mikehill85
Posts: 23
Joined: Wed May 24, 2017 6:31 pm

Re: Anyone ever had Z-banding issues?

Post by mikehill85 » Tue Apr 09, 2019 7:40 am

I did try removing the bearings at the top. There was no noticeable difference in the banding. I've looked at several forums on this subject and, short of replacing the printer, I haven't seen any one fix this problem.

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