Height map have I got it wrong ?

  • I think I may be reading the results of the map wrong ?
    The points above the line are positive and the ones below the line negative , So is the bed curving up or down ?
    If a negative value means it is less that the set point , does that mean that the bed is really curving up ?


  • yes the picture says its curving up.

    if your bed is heated up? this could be due to thermal expansion

  • @Veti

    yep , it also could be the helped by the foil I put in the corners to stop it , but just adding to the problem ..

    Yes a heated bed at 60c

    it is a bad visualiser if you get the wrong idea from it ?
    up should be up

  • @peter247

    no the buildplate looks fine.

    you will however to enable mesh compensation to print on it.

    or get a headed bed with a thicker aluminium

  • @Veti

    I have fitted linear rails , but only to the X axis .
    Before if I did a Hi res height map ( 20mm apart ) I could see a ripple with the wheels being off centre.

  • Moderator

    @peter247 said in Height map have I got it wrong ?:

    it is a bad visualiser if you get the wrong idea from it ?
    up should be up

    If you hold your cursor over the little grey dots you'll see what the offset of those points is. How is the visualization giving you the wrong idea? It's showing you what the surface of your bed looks like? Higher in the middle, lower on the sides.

  • @peter247 the graphic is showing you that the bed is lower relative to the nozzle/probe at the edges (as it is negative). Looks to be near zero at the centre because that's where you have proved to set your Z0 datum.

    One other thing to bear in mind is that there are other sources that can cause the heightmap to be curved like that, not just the bed itself. E.g. your X-gantry could be sagging a bit in the middle (so the nozzle is closer to the bed/the bed is higher in the middle, but slight further away/lower at the edges). Doesn't change how the mesh comp works, but is useful to remember if you're chasing a perfect mechanical system.

    For what it's worth, I'd say that map doesn't look too bad (mine has a lot more droop and prints fine with mesh comp), but definitely do one with more points to get the full detail

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