Auto leveling not working

Troubleshooting talk for software

Auto leveling not working

Postby Chris Knowlton » 2015-May-Sat-11-May

Hi all,

I have a Printrbot simple metal and have been printing successfully for months. But lately it appears that the auto leveling system is not working properly. I tested the Z stop using the M119 command at all three corners and it correctly registers as “0” or “triggered” when the extruder is raised and lowered by hand. My bed is fairly level and the Z motor is moving a little while each layer is printing but it is not compensating (or not compensating enough) when printing. The first layer width varies greatly from one side of the bed to the other.

Any suggestions?

Thanks,
Chris
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Auto leveling not working

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Re: Auto leveling not working

Postby veng » 2015-May-Sat-15-May

Execute a G29 from Pronterface or some similar program but not the Pronterface like UI in Cura which doesn't seem to have an output window that I can find. Hold your hand on the power switch in case of a problem.

You should get three (or maybe four if you changed config.h) co-ordinates in the output window. The X and Y should correspond to where the probe was when testing while the z value is what is used to calculate the plane. There should probably be some difference in the z values or either your bed is extremely level or something isn't working.

It only compensates for tilt in the plane. If the bed is bent, auto-leveling won't cure that.

In an experimental set-up where I'm trying a different sensor than the Printrbot with longer sensing measuring through glass, I'm getting z values of-0.37, 1.48, 1.06, 0.02 on a totally unleveled bed. Obviously I should level it up better than that.
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Re: Auto leveling not working

Postby frankv » 2015-May-Sun-00-May

Something has changed, and it ain't software or electronics. Check for play in the X, Y, and especially Z axes.

If the bed was extremely level, the Z axis wouldn't be turning whilst printing... only intermittently when starting a new layer. Actually, IMHO it is worth levelling your bed to be that level... it takes one, or several, variables out of the problem-solving loop. When you use auto-levelling, an error in one axis can cause a symptom in another axis.
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Re: Auto leveling not working

Postby cacb » 2015-May-Sun-03-May

frankv wrote:If the bed was extremely level, the Z axis wouldn't be turning whilst printing... only intermittently when starting a new layer.


This is true as long as you don't use Z-lifting during moves within a layer. I think perhaps Cura does not do this by default, so it will then be true for anyone staring out with Cura.

I have a fairly level bed and printed a small indicator to be attached to the Z-coupler. I am using the auto leveling probe. There is almost no movement of the indicator even for fairly long moves as long as plastic is being extruded, indicating a "level" bed. However, when moving without extruding and Z-lifting is in effect, the Z axis indicator is turning back and forth very fast, indicating the lifting and "landing" of the hot end during moves within a layer. In my case the Z-lifting comes from a feature in KISSlicer, but I guess other slicers can do the same thing.

It is quite useful to watch the Z axis :ugeek: :)
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