Heightmapping fun... NOT!

[DeltaCon]

For the first time I wanted to try the height-mapping feature because I updated to the 1.17e DC42 firmware with the 1.14a GUI and the show heightmap button got me curious. I repeatedly get these kind of crazy maps though:

Really not fun and I guess that makes my printer unusable if turned on. The routine just runs like I would expect it to. I am using a bit coarse grid of 20mm and a radius of 120 because I have the 0.6 version Duet and that one does not allow for enough probe points needed for a finer grid. What could cause this ENORMOUS deviation figures that are not really there of course?

Here is the map in figures:

Code: Select all

RepRapFirmware height map file v1 generated at 2017-02-27 21:12, mean error 184466663519813632.00, deviation 3026897512028962816.00
xmin,xmax,ymin,ymax,radius,spacing,xnum,ynum
-100.00,100.10,-100.00,100.10,120.00,20.00,11,11
      0,      0,  0.067,  0.035, -0.003, -0.039, -0.088, -0.075, -0.077,      0,      0
      0,  0.139,  0.115,  0.097,  0.070,  0.009, -0.028, -0.073, -0.084, -0.015,      0
  0.023,  0.003,  0.021,  0.014,  0.041,  0.029, -0.021, -0.003,  0.017,  0.035,  0.109
  0.028,  0.023,  0.046,  0.060,  0.061,  0.015, -0.027, -0.038, -0.022,  0.025,  0.099
 -0.053, -0.022,  0.002,  0.026,  0.035,  0.002,  0.009,  0.015,  0.048,  0.090,  0.165
 -0.027,  0.054,  0.060,  0.039,  0.014, -0.018, -0.015, -0.011, -0.011,  0.028,  0.125
 -0.059, -0.027,  0.012,  0.028, -0.003,  0.020,  0.025,  0.015,  0.026,  0.046,  0.118
 -0.087,  0.004,  0.040,  0.038,  0.009,  0.052,  0.024, -0.025, -0.034, -0.022,  0.077
 -0.082, -0.035,  0.043,  0.038,  0.021,  0.013,  0.010,  0.000,  0.002, -0.001, -0.018
      0,  0.011,  0.009,-8224483864962138112.000,16451619751970471936.000,-136651341824.000,1035104029769728.000,  0.138, -0.235, -0.049,      0
  0.000,  0.000,5490524672.000,-753258.250,12635438092820414464.000,-16456320164179214336.000,16443865995971395584.000,-6421816847368192.000,367459303424.000,  0.000,  0.000

As far as I can tell nothing odd is happening at the probing points that go bezirk.

[magicmushroom666]

Are you sure nothing is triggering early?
I was getting something similar, and it turned out my cooling fan was catching on the build plate clips at some locations, causing it to trigger before the nozzle had actually contacted.

[DeltaCon]

Are you sure nothing is triggering early?

Yes I am. I have no fans hanging below the effector momentarily. Besides that would not explain why my triggerheight value is somewhere around the height of the moon... What strikes me though is that the decimal values of the "questionable" triggers are all exactly .000 behind the dot...

[dc42]

We have no other reports of anything like this. Do you get the same bad height values each time you run G29?

Please upgrade to firmware 1.18RC1 and let us know if it is still a problem.

[DeltaCon]

Thanks DC,

You probably have read on the reprap forum that the update to 1.18RC1 looks to give plausible results indeed.
Will have to rerun a few hot calibrations as wel to be really sure. It was too late yesterday so I will do that tonight.
Do I need to change anything in my config.g to enable the dropdown-button mesh grid compensation routine?
I could not find any info googling that yesterday.

[DGBK]

It happens sometimes: http://forum.seemecnc.com/viewtopic.php ... 16#p101555

MHackney's theory is that if the probe points are directly across from the FSR mounts, it can make it teeter or something which causes crazy results. If you look at that thread, he describes his new mounting system that places the FSRs outside of the build plate to eliminate wobble.

[DeltaCon]

It happens sometimes: http://forum.seemecnc.com/viewtopic.php ... 16#p101555
MHackney's theory is that if the probe points are directly across from the FSR mounts, it can make it teeter or something which causes crazy results. If you look at that thread, he describes his new mounting system that places the FSRs outside of the build plate to eliminate wobble.

Yes DGBK I am aware of that issue. Good shot, but there are multiple reasons for me to think I have not the same problem. In Michaels case he could see the "falling back" of the bed by looking at the JSL board. The led's would light. Also I am quite certain that the nozzle really touches the bed at the places where I am getting false figures. As third reason: the fact that the falsely registered figures all end at .000 makes me think there is something wrong in the firmware calculations. That simply cannot be a coincidence... Also I used a grid radius of 120 because my duet (0.6) cannot handle enough probepoints, and that radius is within the "safe triangle" as shown in Michaels infographic.

I took DC's advice and installed the 1.18RC1 and I did a few mesh grid compensations cold as well as hot, and the strange behaviour did not return. Thanks David, for the suggestion! And thanks DGBK for thinking along with me!