Auto Bed Level on Prusa - No response to G29

I have setup the auto bed levelling (tired of manual levelling) on my Prusa i3. However I am running into an issue. When I home all the axes (run G28), all the axes work fine. Even the z-axis, the servo arm is extended, the z-axis lowers until the end-stop is triggered, it stops, retracts a little bit, lowers slowly again, end-stop is triggered again, and the arm is retracted. So it not only works perfectly, it also recognizes the fact that there is an auto bed levelling mechanism in place, since it extends and retracts the arms.

However when I do G29 to kick off the auto bed level procedure, nothing happens. Nothing moves. No x-axis, y-axis or z-axis. Nada.

I read posts about some axes moving but not others, but I couldn't find any post with no axis moving at all.

Any idea anyone?

Thanks.

I have the same problem. I hope someone has a fix for this.



{Upddate:}


I downloaded the latest Marlin firmware and it works now.

Edited 1 time(s). Last edit at 09/08/2014 11:15PM by jpace7.

I finally overcame this issue and then a couple of more, but now it is able to perform a 4-pt test and then it starts printing. If I feel z-axis with my hand I can tell it is moving slightly as X and Y move while printing, so all this looks great.

Except the print itself is totally messed up. See the attached. It is supposed to be a test cuboid 3cm x 3 cm base and 2cm height with almost 2.8 cm dia hollow cylinder in it. The circle for the cylinder before auto bed leveling used to come out to be a perfect circle but as can be seen the circle is full of blobs of filament. The in fill also appears to be over extruded. Note that it was all working fine before auto bed leveling.

I can see that the extruder motor is not turning/extruding uniformly. It turns a little bit, stops, and then turns again, whereas before it would continuously extrude as it would print, until it has to travel in which case it would retract first. Here it turns, then stops, and then turns, and my feeling is that it turns enough at once to compensate for the stop, but the side-effect is that I see blobs of filament all over.

My hypothesis is that the calculations for moving z-axis for auto bed leveling are so involved that they cause interrupts/delays in the extruder motor and other motors' control, causing them to move abruptly. But then again, everyone has same kind of hardware (Mega + RAMPS + Polulo), so why would I be the only seeing this issue.

If anyone has any ideas, I would love to hear about them.

Thanks.

I undid the auto bed levelling from configuration.h, and moved my end-stop back to z-axis from the servo, but I still continue to have the same problem.

Looks like it is either the hardware issue or the configuration isn't quite undone yet. Something I changed while setting up auto bed level is still in effect and is causing this issue!!! Very frustrating.

This is something that I've very interested in as well and will definitely attempt once I have my printer and is dialed in well enough, but to start I do have two questions for you:
1). Is this the first printer you've set up auto leveling on? (Not to try and judge experience level, just wanted to get an idea of if this is a new problem because it's the first time or if it's just a fluke with this printer)
2). Have you made a lot of changes from the stock firmware? (Humor me)
Hope I can be of some help in resolving this issue for you (and future me when I cross this road)

Hi NarimaanV,

Thanks for your response.

1) Yes this is the first and only printer I have every built.
2) I haven't made any changes other than the ones in configuration.h. I am using almost the latest (about a couple of weeks old) Marlin firmware from github. I am not using the stock firmware.

Everything was working great before setting up Auto Bed Leveling. But in order to debug the G29 not responding issue, I added quite a few debug messages in marlin_main.cpp file. So in addition to configuration.h file changes to setup Auto Bed Leveling, I had some debug messages. But since then I have removed all the debug messages and have disabled Auto Bed Leveling but it continues to do the same thing.

One more observation. On my LCD screen (yes I added an LCD screen as well) the z axis seems to be raising with the increments of 1 mm per two layers as it prints. What I mean is that the print goes through two layers but the z axis does not move up, and then it moves up 1 mm for the next two layers and so on. All this is weird because the layer height is either set to 0.4 mm when I slice which means it should be raising 0.4, 0.8, 1.2 and so on....

Anyways I have just downloaded the latest and greatest from github and have sync'd up my configuration.h file with the version I had before. I just need to try it out. I will keep you updated.

Quote
NarimaanV
This is something that I've very interested in as well and will definitely attempt once I have my printer and is dialed in well enough, but to start I do have two questions for you:
1). Is this the first printer you've set up auto leveling on? (Not to try and judge experience level, just wanted to get an idea of if this is a new problem because it's the first time or if it's just a fluke with this printer)
2). Have you made a lot of changes from the stock firmware? (Humor me)
Hope I can be of some help in resolving this issue for you (and future me when I cross this road)

Ahh ok, yes everything you say does sound very strange, and you actually read my mind in terms of what I was going to suggest to you, which was to just re-download the latest marlin and just change what is necessary to make the printer work with manual leveling, that way if it still acts up, something went wrong hardware-wise. I look forward to hearing the results of the new firmware

I tried the latest firmware and it fixed the issue. So there was something that I did which I could not undo in the firmware that caused it.

Okay that's good, a software issue is almost always better than a hardware issue so at least that possibility is eliminated. Now there's a short YouTube playlist (only 3 about 10-minute videos) of this guy setting up auto bed leveling with his Prusa i3 (his is from Makerfarm but the overall process should be pretty much identical for our i3x's as well) and I think he does a pretty good job going through every step both hardware- and software-wise (though it seems you have the hardware set up, so only the software would be of much help for you) of setting up auto leveling, so I suggest you try and do almost exactly what he does if possible, and see if it works.

Here's the link to the playlist (if you want to skip straight to his software configurations, you can start at the second video): Auto Leveling Playlist

Thanks. I used those videos to setup mine. For whatever reason I ended up in running into this issue. I don't think he did.

The only thing that I noticed when I was updating the new configuration.h file, while comparing it against existing configuration.h file, is that I had max endstops disabled as part of setting up the Auto Bed Leveling. I did not enable it back when I undid the changes for ABL. I left it enabled in the new firmware. I can't imagine how that would cause extruder to go hay wire, but maybe somehow the bug is related to that.

For now things are working and I need to print out some models. Once I am done with them, I might go back and enable max endstops in the previous firmware configuration and see if that fixes the problem. There is a good chance that it will - can't explain it how - but that's the only thing significant that I noticed that was left over from undoing the changes for ABL.

Edited 1 time(s). Last edit at 09/11/2014 10:44AM by shah123.

What do you mean by "max endstops" exactly?

From what I understand is that Marlin firmware implements the software based max end stops. So when it hits the hardware end stop, it calls it 0 and you set the size of your bed, and that allows it to compute the max end stops, which means that it won't let the axis move beyond that value. I know older firmware (a year or older) did not have this feature. This is something added later. It is a safety feature.

Wait but why did you turn that off when you did auto-leveling? From what I understood, the only endstop related change was disabling not being able to go below your MIN endstop value (i.e. the line "#define min_software_endstops true" being made false to let you make negative z-values to tune the probe)?

Huh, did I disable the wrong one? I will have to look. I won't be surprised if I did that. :-)

I certainly hope this whole thing was caused by just simply changing the wrong line

Ok, I changed #define min_software_endstops true to false which was correct. But one more thing that I did and I think I read about it in some forum, someone pointed out that there are two more #defines which are related to min and max endstops:

//#define DISABLE_MAX_ENDSTOPS
//#define DISABLE_MIN_ENDSTOPS

They are both commented out by default. And they said they only uncommented this #define instead of setting the other one to false. I went ahead and "tried" to do both to cover my bases. But unfortunately for this one I ended up in uncommenting the max one instead of min one:

#define DISABLE_MAX_ENDSTOPS
//#define DISABLE_MIN_ENDSTOPS

This might very well be what my problem was. I will flip it and try it out, or may be I will just leave both of them commented out. I will update you.

Okay great can't wait to hear about what happens

Had any time recently to test the new settings?