Strange lines in heightmap



  • Does anyone know a reason to why I'm getting these weird lines in my heightmap? The lines are higher when moving from negative to positive x coordinates, and lower on the way back. I'm using an smart effector to probe on a glass bed. Any thoughts or recommendations?



  • I don't know why, but FWIW, I've seen the same sort of accordion pattern on mine. I saw the same thing when I was using an inductive probe, before I got fed up with it and bought a Smart Effector, too, so I don't think it's specific to the Smart Effector. The actual first-layer height seems to come out OK, so investigating this has been a low priority for me.



  • The smart effector is the first probe I got, so i cannot say if this pattern is specific to that or not. I just thought I'd include it so people know what type of probe I'm using and on what surface šŸ™‚



  • If you rotate the bed 90 degrees, does the pattern change? If zo, it's just how your bed is (and I would replace it!) but my guess is you have a mechanical problem. Especially your statement that it is worse moving to higher X values indicates that there is probably a belt problem, or loose pulley.


  • administrators

    I'm fairly sure that lines along the X direction like that indicate backlash in your mechanics. As you have corrugations at both ends but in opposite directions and more or less independent of Y, I think both your X and Y carriages have backlash. This could be caused by friction or by insufficient motor current.

    What I don't understand is the ridge of blue areas running in the Y direction.



  • I'm running 1mA on each motor, maybe that too low since im running at 12Vā€¦ Gonna try and increase the current a little and rerun the mesh. What is a normal current for these specs? 1.2mA?

    The bed is held by three "tabs" similar to these: https://www.thingiverse.com/thing:646471. Which is placed in the lower left corner, top left corner and slightly lower than the right middle which could explain that it is higher in those areas. Unsure why its not lower in the middle left though.


  • administrators

    I presume you mean 1000mA and 1200mA (1A and 1.2A). Normal motor current is between 60% and 85% of the rated current of the motor.

    I suggest you check that the carriages run freely up and down the towers when the rods and belts are disconnected. Unless they are extremely light, they should drop under their own weight.

    Lubricating the magnetic ball studs may also help - I use silicone grease on them.



  • I got a similar pattern with my KosselXl BEFORE switching to the smart effector: https://www.duet3d.com/forum/thread.php?id=3669
    I couldn't find any 'real' backlash (wiggle room when using minimal force), but noticed my carriages are very soft and could flex quite easily with a moderate amount of force. I redesigned the carriage to be much stronger (https://www.thingiverse.com/thing:2807725) and printed in PLA instead of PETG as its less flexible and the problem was much reduced.

    After switching to the smart effector it got better again, but thats probably because there is no offset as with the mini differential ir sensor so the effector tilt isn't that bad for height calibration. I don't think there was anything wrong with the traxxas rods or metal effector i used before.

    I was surprised how easily the 2020 extrusion towers could be twisted by hand, wouldn't build a KosselXL again with 2020 and use 2040 instead, which extrusions are you using?



  • I presume you mean 1000mA and 1200mA (1A and 1.2A). Normal motor current is between 60% and 85% of the rated current of the motor.

    Yes I ment 1A, forgot to remove the milli after the conversion. I've increased the current to 1.3A but it had no effect on the pattern.

    I suggest you check that the carriages run freely up and down the towers when the rods and belts are disconnected. Unless they are extremely light, they should drop under their own weight.

    I use the typical kossel carriages and they did drop of their own weight until i tightened the horizontal screw through them to lower the chance of warping in the Z-axis. It might not be needed anymore since I switched from the traxxis rods i used before.

    Lubricating the magnetic ball studs may also help - I use silicone grease on them.

    Gonna go get some tomorrow to give it try.

    wouldn't build a KosselXL again with 2020 and use 2040 instead, which extrusions are you using?

    Oh I'm using 1515 rods, which is one of the reasons i tightened the carriages. The carriages is printed in PLA and from what I recall the "handle" didn't flex that much but since I have a horizontal screw through it it cannot flex that way while assembled.


 

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