Mesh Bed Compensation Effectiveness



  • Hi,

    The heightmap.csv files allows us to look at the bed BEFORE mesh bed compensation. Yes? No?

    Is there anyway to visualize or otherwise determine how flat the bed seems to be when the compensation is enabled?

    I've taken a few measurements using a dial indicator and it isn't measuring as flat as I thought it would.

    Thanks.

    Frederick



  • Follow on:

    Just out of curiosity I thought I would measure, using the dial indicator, at a few points both with mesh bed compensation on and off - at least on and off as reported by the DWC.

    I used just a few points for these first few measurement. The center (X=0 Y=0) and the probe points corresponding to the X, Y and Z tower positions as generated by the auto calibration probe generating utility.

    Much to my surprise there were no differences (within the accuracy of the dial indicator) with mesh bed compensation on or off.

    Color me confused.

    Can anyone educate me as to why this could be so?

    The mesh bed compensation is effective for the DWC movement controls isn't it?

    Thanks.

    Frederick



  • I guess it would depend a lot on how far from flat your bed surface is. And how close your Z=0 probe point is to the average.

    In my setup, my bed has a bulge at one corner, but the rest is quite flat. With compensation on I can see the Z axis motor moving as it approaches the bulge to maintain the same distance from the bed. With it off the nozzle tip would hit the bulge.

    The best indicator of how flat the bed I have is to print this file.

    0_1536965680437_bedlevel_nozzle_0.4_200x200-0.3-0.8.stl

    Mind you my setup is a corexy. And you're using a delta, so you have a lot more to deal with.



  • Hi,

    Thanks for the feedback.

    I'm running heater tuning on that printer so I cannot provide you with a picture of heightmap.

    When I can I will.

    I don't think the heightmap is so flat that there is no compensation for the firmware to do but I'm not sure.

    Frederick



  • Hi,

    Here is my heightmap with .txt added up so it would upload.

    Drop the .txt and you can view it in DWC.

    0_1536977920544_heightmap.csv.txt

    Thanks.

    Frederick



  • 0_1537039390144_Screenshot 2018-09-15 13.21.30.png

    Does that look right? It looks like only half your print bed.



  • Hi,

    To check I download that file, opened it and copy the contents into a file name test.csv on one of my printers and viewed it.

    It was a complete "circle".

    Thanks.

    Frederick



  • @fcwilt I wonder if it's being limited by my bed maxima. What do you have?



  • @phaedrux said in Mesh Bed Compensation Effectiveness:

    @fcwilt I wonder if it's being limited by my bed maxima. What do you have?

    It's a mini-delta. I use 160mm as my diameter.

    Frederick



  • your not above the fade height when you take those measurements?



  • @gavatron3000 said in Mesh Bed Compensation Effectiveness:

    your not above the fade height when you take those measurements?

    Hi,

    I don't know what the "fade height" is - never heard that term.

    Frederick







  • Interesting so far but back to one of my original questions.

    Is there anyway to determine what a height map might look like when mesh compensation is working?

    Or is there any documentation that describes in greater detail the workings of mesh compensation?

    So far I have not be able to determine if it is doing anything on this printer. Dial indicator measurements have been the same with and without mesh compensation. Curious.

    Frederick



  • Given that the output of a mesh is just a csv... hand edit it to have some reasonable slope, but large, values, save it, reboot.

    Activate mesh and do your dial again.

    Maybe??



  • @fcwilt Are you sure it's being applied?

    If you run M122 there should be a line saying Bed compensation in use: mesh

    Do you explicitly load the heightmap anywhere with G29 S1?



  • And to be clear, there are several things that DE-activate mesh... like G32 (which is in my print start script, for a smart effector)... so be sure a G29 S1 is in your "print start" (and that you've done one yourself when you dial to check).



  • @danal said in Mesh Bed Compensation Effectiveness:

    Given that the output of a mesh is just a csv... hand edit it to have some reasonable slope, but large, values, save it, reboot.

    Activate mesh and do your dial again.

    Maybe??

    That's a very good idea. I will try that.

    Thanks.

    Frederick



  • Well at the start of the print the DWC reports mesh compensation is in effect.

    Before taking my measurements with the dial indicator I have verified the state using the DWC.

    Thanks.

    Frederick


 

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