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User guide to UBL?

Posted by DaveA 
User guide to UBL?
May 06, 2017 04:34PM
Is there a step by step set of instructions for using UBL? I'm using 1.1.0 with a BLTouch. Following the steps I think I need I initialized EEPROM, did a G29 P1 to create a mesh and saved it to EEPROM with G29 S0.
I activate UBL, load the mesh and then try to print but there is no obvious correction taking place. The only time Z moves is when changing layers.

Anything else do I need to do in my start print script?
Re: User guide to UBL?
May 06, 2017 06:56PM
Yes... All that sounds reasonable! You may need to do a G29 A to activate it. But... I've fallen into this trap several times during development. Is your nozzle more than 10mm above the bed? If you move your nozzle to 1mm above the bed, you will see movement if the system is active. You can look at your topology map by doing a G29 O

Or, if you want more extreme proof the system is working, do a

  • G29 P0 ; to zero the mesh
  • G29 Q1 ; to put a diagnol line across the mesh
  • G29 A ; to activate system
  • G29 O ; to view the test pattern
  • G1 Z2 ; to get the nozzle within the fade height
  • G1 X0
  • G1 Y 100
  • G1 X 150

You should see the nozzle rise as it hits the line and lower when it gets past it....

Incidentally... There is a Quick Start guide available now... Bob-the-Kuhn wrote it. If you search a little bit at www.github.com/MarlinFirmware/Marlin you should be able to find it.

Edited 2 time(s). Last edit at 05/06/2017 07:05PM by Roxy.
Re: User guide to UBL?
May 08, 2017 12:51PM
Incidentally... There is a Quick Start guide available now... Bob-the-Kuhn wrote it. If you search a little bit at www.github.com/MarlinFirmware/Marlin you should be able to find it.

I've been trying to figure out UBL all weekend without much luck. I found Bob-the-Khun's guide here: [github.com]

And that did seem to help me generate a mesh. But...doesn't really explain how to use the mesh.

With traditional bed leveling I just add a G29 after my G28 in my startup gcode and I get leveling.

What needs to be done once you've got a mesh to actually use it with UBL? The Guide doesn't really say. I see a new script generated 'buildroot/share/scripts/g29_auto.py' which has a comment at the top saying it's "for preprocessing gcode and the new G29 autobedleveling" and something about replacing "g29_keyword = ';MarlinG29Script' with "the new G29 LRFB" not sure if this is related to UBL or is an old thing left behind...I've never noticed the script before so I'm not sure.

I tried just using G29 A and that didn't seem to work...so I tried G29 A followed by G29 J 2; and that didn't seem to work either...I could see it probe before printing but then it raised the print head up and tried to print about an inch above the printbed and way off on the side of the buildplate instead of the center where it should have been.

The instructions on how to improve the mesh are also pretty sketchy still. I did a G26 and none of it looked great...but I'm not sure how to interpret it. I measured some of the extruded material and it was 0.20 which is what the G26 was supposed to do...but it wasn't a clean extrusion - lots of gaps. One corner of the mesh definitely looked like it needed to be improved - but the instructions on using P4 seem incomplete in Bob's guide. And reading the instructions in ubl_G29.cpp didn't help much either...it just says things like "Using the information left on the printer's bed from the G26 command it is very straight forward and easy to fine tune the Mesh" But doesn't really go into any detail about what you're supposed to do. It may be straight forward and easy if you understand the intent...but I can't find anywhere that it's all explained.

Looking forward to trying this - I'm getting better prints off 1.1.0 (and bugfix-1.1.x) than I was off RC6 which I had been running previously. And I'm very excited to try the new UBL stuff. Just lost since the documentation seems to be mostly written for people who are already familiar with UBL at this point.
Re: User guide to UBL?
May 08, 2017 02:37PM
Same here, went back to bilinear instead of UBL. Will try it again once there is a " UBL for dummies"
Re: User guide to UBL?
May 09, 2017 06:03PM
UBL User's Guide at: [marlinfw.org]
Re: User guide to UBL?
May 10, 2017 01:48PM
The UBL getting started guide is now available.

We will be changing the firmware so that the LCD is all that is needed to do 99% of the UBL bed leveling. The changes should be in the bugfix-1.1.x branch later today.
Re: User guide to UBL?
September 17, 2017 01:05AM
I am really hopeful for UBL to work properly one day. I spent about 5 hours trying to use it today, reading the user guide, and no luck. It sort-of, almost works... just enough to tease me into continuing to try. The manual is great at explaining steps that should work properly, but I think it also doesn't help you understand what's going on. The fact that it is also just wrong in some cases doesn't help.

Let me focus on the fine-tuning, since that's where I am right now. I did the cold probe, then smart-picked the other locations. I'm not at all sure why this is needed, since it was for points that were perfectly fine to probe. The addendum was wrong. The machine probed those points... why doesn't it keep the value it measured with my probe? No idea. But no bother, I figure I can simply adjust it. So I use the manual tuning with G29 P4 T. First, I go to one of the probe X/Y points, and then go to Z0 (all of this with the UBL activated, something it took me about 20 minutes to realize I had to do!) Now, I have the piece of paper, and see that it doesn't fit under the nozzle. The nozzle is resting on the bed. Great, so I need to adjust this mesh point up a bit... perhaps 0.1mm. G29 P4 T. The LCD shows 0.015. Unfortunately, the nozzle has been moved up, perhaps 0.75mm. Why didn't it stay in place so that I could use the paper feeler? Instead, I have to guess and check. I change it up to 0.115. During this, the nozzle is moving, even though the user guide says it won't (in bold). I save. I print the mesh to host to see that yes, it is now 0.115 at that point. I issue another G1 Z0, and the nozzle is still resting on the bed. Hmm. I repeat this, changing by 1mm.... this time, the nozzle is a tiny bit over the bed, but not enough for the paper to fit (normal paper, not super-fat 2mm paper, I promise!). I repeat and go about 5mm. This time, it goes up perhaps 1mm. Are these units actually mm, or something else? I'm very confused.

Should I edit the user guide and add my problems and these confusion points? Should I add something about how the Z-offset of my probe is completely ignored? (Changing it artificially by 2mm didn't change the cold-probe results by 2mm... I would think it should, but I don't understand what's supposed to happen... the documentation just isn't there.) What happens when I move the nozzle and UBL isn't activated? Does that mess something up? An explanation of how this works would be nice.

Massive apologies for this tirade. My next step is to dig into the code. I'm capable of a pull-request, so maybe I'll try that. But if I'm going that direction, I might just make some advanced values to manually offset the bilineal mesh values. No where near all of the excellent UBL features, but I think I could make it work.
Re: User guide to UBL?
September 17, 2017 10:38AM
Any help getting the documentation fully in sync with the code base would be appreciated. First... Hopefully you were able to print a small object at the center of the bed with no bed leveling active. If so...

It sure seems like the bulk of your problems are because of the manual probing. You really don't need that. Just fill the unreachable locations with G29 P3. You can then do a G26 and use that to edit any mesh points that are not perfect.

Why don't you give that a try?
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