Objects are placed below the print bed

When I import an object into Repetier-Host, it is placed a fraction of an inch below the print bed, which cuts off the bottom of the object and seems to cause problems with slicing. I've tested this with both my own Sketchup STL exports and with several Thingiverse STL files.

I'm not sure how to fix this, and can't find anything in the various menus. Please help!

Comments

  • So do you see the object from below the bed with same color as from top without being darkened from bed? I ask because that should not be possible. Slicers on the other side have a setting to cut a but of the z so they start higher with slicing. That can be useful if the objects bottom is a bit wavy and will not stick to bed.
  • edited April 28
    Yes, if I rotate the view to below the object, I see the lower section is bright blue and the top section is darkened by the bed. If I zoom inside an object, I can see the bed surface cut through the bottom of the object.

    I only noticed it because I was printing a game chip of .1" in height and it was printing too thin.  I had to make it .15" high to get the desired thickness.

    So we're only talking about .05"; but from what you say it might be intentional.  If it isn't I can't figure out how to fix it.
  • Can you send me the object model? Haven't seen this happening without explicitly telling host to do so. Normally it lands a object on adding so that this is not the case. Only if you explicitly move in z direction it should happen. SO maybe the object gets parsed wrong by host.
  • Sure, I'll send it tonight. Just the STL file or the Sketchup file as well?
  • edited April 30
    The forum won't let me post an STL file directly, but here is the code for a simple box which exhibits the problem:

    solid box test
    facet normal 0.0 0.0 -1.0
      outer loop
        vertex 2.54 2.54 0.0
        vertex 0.0 0.0 0.0
        vertex 0.0 2.54 0.0
      endloop
    endfacet
    facet normal 0.0 0.0 -1.0
      outer loop
        vertex 0.0 0.0 0.0
        vertex 2.54 2.54 0.0
        vertex 2.54 0.0 0.0
      endloop
    endfacet
    facet normal -0.0 -0.0 1.0
      outer loop
        vertex 2.54 0.0 0.254
        vertex 0.0 2.54 0.254
        vertex 0.0 0.0 0.254
      endloop
    endfacet
    facet normal -0.0 -0.0 1.0
      outer loop
        vertex 0.0 2.54 0.254
        vertex 2.54 0.0 0.254
        vertex 2.54 2.54 0.254
      endloop
    endfacet
    facet normal -0.0 -1.0 -0.0
      outer loop
        vertex 2.54 0.0 0.254
        vertex 0.0 0.0 0.0
        vertex 2.54 0.0 0.0
      endloop
    endfacet
    facet normal -0.0 -1.0 -0.0
      outer loop
        vertex 0.0 0.0 0.0
        vertex 2.54 0.0 0.254
        vertex 0.0 0.0 0.254
      endloop
    endfacet
    facet normal -1.0 0.0 0.0
      outer loop
        vertex 0.0 2.54 0.254
        vertex 0.0 0.0 0.0
        vertex 0.0 0.0 0.254
      endloop
    endfacet
    facet normal -1.0 0.0 0.0
      outer loop
        vertex 0.0 0.0 0.0
        vertex 0.0 2.54 0.254
        vertex 0.0 2.54 0.0
      endloop
    endfacet
    facet normal -0.0 1.0 0.0
      outer loop
        vertex 0.0 2.54 0.254
        vertex 2.54 2.54 0.0
        vertex 0.0 2.54 0.0
      endloop
    endfacet
    facet normal -0.0 1.0 0.0
      outer loop
        vertex 2.54 2.54 0.0
        vertex 0.0 2.54 0.254
        vertex 2.54 2.54 0.254
      endloop
    endfacet
    facet normal 1.0 0.0 0.0
      outer loop
        vertex 2.54 2.54 0.0
        vertex 2.54 0.0 0.254
        vertex 2.54 0.0 0.0
      endloop
    endfacet
    facet normal 1.0 0.0 0.0
      outer loop
        vertex 2.54 0.0 0.254
        vertex 2.54 2.54 0.0
        vertex 2.54 2.54 0.254
      endloop
    endfacet
    endsolid box test

  • Ok, I see what you mean and it is no real error. It is more a optical illusion due to the fact that the bed coordinates are shifted a bit toward the user so lines on bed are normally good visible also from below. Now your object is soo small as it is loaded in mm that you can see very well the trick used here. That is not the reason the chip has not the right height. Your height might differ a layer height since slicers slice at steps of layer height. If your error is bigger there are several reason. Z homes not correctly so it starts deeper or z steps per mm are not set right.

    As a simple test check in your gcode printed what the biggest z height is there. That should be the height of your box. If not you need to calibrate. First layer also adds normally a tiny mismatch so small errors are ok but 1.27mm is not small.
  • Thanks for your help and patience! So for very small objects, I should just make them 1.27 mm higher?
  • No, making objects 1.27mm higher only works around an error. Big object will also have wrong height I guess. You need to find the configuration setting that is wrong. Z home position, z steps per mm and z acceleration being too high so you loose steps or z max speed to high loosing steps are the values to test. Get a metal block of known height and home and go with z to that position and see if it fits below nozzle with only a light scratching. Do this with a higher block as well. If that succeeds your z parameter should be calibrated good.
  • Sounds good, I'll look for those. Thanks!
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