Bed height map - Wrong result data

I have a RepRap Delta printer with Repetier firmware 0.92.3, and I have metal heat bed with leveling in 3 points. Bed is correctly leveled mechanically.

I have calibrated carriages on all three towers with rod as in your video tutorial, and double checked geometry of the printer with laser measuring device (0.1 mm resolution) and metal meter and everything is OK.

Printing with 0.1 mm layer height is excellent and even on the whole bed.

But, when I try to measure levels with micro-switch probe mounted on the print head, with Bed height map option in the Repetier Host, I got wrong results. Only center point is correct. Why is that? What I am doing wrong, because printing is OK end even on the whole bed?

I got results Min Height: 11.82, Max Height 15.33, Center Height 14.11. Maybe I can make level mistake of 0.1 mm, but more then 3 mm no way.

Please advice.

Thanks in advance.

Dragan Kujovic


  • Do you go down to Z=12 before starting height map? Depending on your starting point you can hit a endstop - especially if you start after homing. That stops the move on that axis and gives your setup a skew it did not have after homing.
  • Yes. I first send G28, and after that G1 Z12.
  • Real Z = 14 mm
    Measured data:
    12,36 12,10 12,07 12,27 12,48 12,49 12,27 12,04 11,82
    12,97 12,85 12,93 13,00 13,07 13,15 13,02 12,95 12,64
    13,52 13,58 13,57 13,58 13,50 13,44 13,38 13,25 13,22
    14,09 14,09 14,16 14,00 13,87 13,66 13,56 13,63 13,62
    14,49 14,53 14,47 14,36 14,16 13,97 13,93 13,91 14,04
    14,80 14,84 14,72 14,56 14,44 14,34 14,24 14,32 14,34
    15,01 14,94 14,89 14,77 14,70 14,68 14,66 14,61 14,63
    15,20 15,13 15,03 14,98 14,96 14,98 14,95 14,90 14,85
    15,33 15,25 15,18 15,16 15,18 15,23 15,20 15,12 15,06

  • I have checked this wrong results data at Bed height map measuring, and noticed that nozzle hole is even to the surface of the mechanically leveled bed no matter where the nozzle is on the bed, but the angle of the extruder carriage is changing.

    So, the probe pin which is 42 mm in front  of the nozzle center (Y axis) has a difference in height of 4 mm from Y=80 to Y=-80 because of the extruder carriage angle changing.

    I thought that extruder carriage is always at the angle of 90 degrees to the surface, but in my case it is not.

    To mention again, I have a RepRap Delta printer:

    Firmware is Repetier 0.92.3.

    Diagonal rod length is 214 mm, Horizontal rod radius is 116 mm and printer radius is 140 mm.

    What could be wrong.

    Any idea? Anybody have this printer, and have tested it with bed height map?
  • Ok, if the carriage changes the angle it is a real problem.

    Delta mechanic prevents this (normally). The constrain to keep it parallel is that every 2 paired arms have exactly the same length and ALWAYS keep parallel, meaning the slider distance and carriage distance must be exactly equal. So I guess at least one pair violates this.
  • Arms are exactly the same length, but one of the tower carriage sliders is not the same thickness as other two !?! Because of that Z axis is longer than X and Y axis.

    I will make all 3 tower carriage sliders on the other 3D printer, and post the results.
  • Different thickness will cause wrong print results but will not change carriage angle. The angle is here physically fixed by the 3 parallelograms. If arms have same length there might still be the distance at carriage and slider which could be different. 
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