Large Variance in Height Map



  • Hello all!

    I have been having some issues with leveling out my bed. I have SeeMeCNC Rostock Max v2 (first run) that has been upgraded with the injected molded skates, trick laser ball arms, smart effector w/ e3d v6.

    I have run my height map and they are all over the place and I don't even know where to begin, so any help would be greatly appreciated, you can find the height maps below.

    Also there is the obvious glaring issue that the smart effector is made for the magnetic ball arms, but having spent a fair amount on the trick laser arms and also because I have had a bad past with the magnetic arms, I was not willing to update to magnetic arms. There is a picture of my effector, however I don't believe that it is causing the issues (hopefully)

    Top view (z tower at bottom of pic)

    Right view (z tower on right)

    Front view (z tower in rear)

    Effector with Ball Cup Conversion


  • administrators

    I believe those ridges are caused by backlash in the mechanics. Possible causes:

    • Loose belt
    • Loose joints
    • Sticking joint or carriage
    • Motor current too low to overcome friction

    From the pattern I would guess that the problem lies in the Z carriage motion assembly, but I may be wrong



  • @dc42:

    I believe those ridges are caused by backlash in the mechanics. Possible causes:…

    I actually have some new belts on order already because I thought that could be a contributing factor, but I will definitely check the carriage for its smoothness.

    However, I have never really messed with the stepper currents. I do know I am using the stock #s that came with the duet, which I realize now probably isn't the best method.
    My M906 command looks like: [c]M906 X1000 Y1000 Z1000 E800 I6[/c]

    Do I need to change and these and keep testing to look for effects?

    Thanks as always for the help.


  • administrators

    I suggest you look up the rated current for the stepper motors you are using, and set the motor current to between 60% and 80% of that current. But low motor current alone doesn't explain those ridges.



  • I think the largest contributor is the belts. Having looked into correct tension, I am going to see if I can get them adjusted, but may have to wait on the new ones because these are quite old.

    Could belts and motor currents be enough to cause this?



  • Actually that isn't the issue at all. Just did two different types of tension, one aggressively tight and one more in the middle between the two and I got an almost identical height map for both of them compared to the original height map posted here.

    One thing I have noticed after changing to the smart effector was that there is quite a bit of effector tilt. However, I believe this was also an issue with the old effector. Could that be causing these variations?


  • administrators

    Effector tilt won't by itself cause those variations. You definitely have some backlash somewhere. Are the carriages rotating about their faces at all when the belts pull them up and down?



  • It doesn't seem to be. If I hold the carriage and twist it, I can definitely some play from side to side. But that is inherent on how the injected molded seemecnc carriages work. Because the use the flexible plastic parts to keep it snug against the extrusion there is play of it is forced.

    I did run a mesh and watched the carriage and didn't observe any twist as it moved. Looking at the heat maps the high points are where the mesh starts a new row and then the readings get lower and lower until the start of a new row and its only on the edges furthest from the x and y towers. Again however I don't know what that means unfortunately.

    I am going to run a mesh with a smaller diameter and see how that comes out.


  • administrators

    What appears to be happening is that the height of the nozzle at a particular point depends on whether it was approached from the +X or the -X direction. The fact that the issue doesn't occur at points that lie on X=0 suggests to me that the issue lies with the Z carriage movement or the associated bearings.

    Try sending G91 and then make small Z carriage movements e.g. G1 S2 Z0.5 and G1 S2 Z-0.5 alternately, and check that you are getting carriage movement.


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