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    Mesh Bed Compensation Screwy

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    Tuning and tweaking
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    • CHPundefined
      CHP
      last edited by

      Ok, so I loaded GrodanB's heightmap.csv and then sampled the whole bed ( HeightMap::GetInterpolatedHeightError() ) with a 4mm (and 2mm) resolution and visualised the result with excel.

      The first one is rather off, the area clearly wrong. Debugging it showed that GridDefinition::recipSpacing is still at its default value (for a 20mm grid) after loading the .csv.

      After fixing that it is much better, but still some hard jumps at the borders, so I'll debug the border-interpolation next.

      My fixes as well as the (very shoddy) simulator I use can be found here: https://github.com/ChristophPech/RepRapFirmware

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      • 3dprinting meatheadundefined
        3dprinting meathead
        last edited by

        I just made a short video of the smooth motion without g29, and the choppier motion with.
        I'm not sure if it's a bug, maybe all the variables eat up the processing power?
        But I don't remember my 8 bit board doing this.
        Here's the video:
        https://youtu.be/igNx0sjtSqE

        If I can learn it, than anyone can learn it.

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        • CHPundefined
          CHP
          last edited by

          I found an error in one of the interpolation functions and fixed it (pull request pending)

          The result looks much better:

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          • CHPundefined
            CHP
            last edited by

            But there is still more. Zeroing out the last two columns gives me this:

            The interpolation overflows into the first column of the next line. Fixing it:

            The final result of the whole mesh: looks quite good.

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            • CHPundefined
              CHP
              last edited by

              And we can even do better by using bicubic interpolation:

              Since Z is often the slowest axis, smoothing it out will mean smoother movement for the other axes.

              But there still remain two last issues: unprobed points with a 0 csv are being clamped to zero, this can easily be fixed

              Second: points outside the probing area remain constant. These should be extrapolated, maybe something like linear regression.

              Thoughts?

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              • dc42undefined
                dc42 administrators
                last edited by

                @CHP, many thanks for diagnosing and fixing these issues. I have accepted your pull request, and I will release a new 1.18 beta soon incorporating these changes.

                Duet WiFi hardware designer and firmware engineer
                Please do not ask me for Duet support via PM or email, use the forum
                http://www.escher3d.com, https://miscsolutions.wordpress.com

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                • pcsentinelundefined
                  pcsentinel
                  last edited by

                  Hi CHP, can I just say thank you for identifying this and fixing, very very much appreciated.

                  DC42, have you any idea what going on re my comment about 4 pont adjustment above?

                  thanks

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                  • 3dprinting meatheadundefined
                    3dprinting meathead
                    last edited by

                    @CHP although I only understand have of what you said(the hampster wheel in my head is seizing up), the pictures you put up show that you've found a way to wrangle the angry pixies flowing to my motors, and I thank you for it.

                    If I can learn it, than anyone can learn it.

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                    • dc42undefined
                      dc42 administrators
                      last edited by

                      @pcsentinel:

                      Hi CHP, can I just say thank you for identifying this and fixing, very very much appreciated.

                      DC42, have you any idea what going on re my comment about 4 pont adjustment above?

                      thanks

                      You need to probe clockwise round the bed, not anticlockwise. One of these days I'll get round to either re-ordering the points or generating an error message if they are in the wrong order.

                      Duet WiFi hardware designer and firmware engineer
                      Please do not ask me for Duet support via PM or email, use the forum
                      http://www.escher3d.com, https://miscsolutions.wordpress.com

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                      • pcsentinelundefined
                        pcsentinel
                        last edited by

                        Hi, tried this which is clockwise

                        G30 P0 X151 Y151 H0 Z-99999
                        G30 P1 X151 Y49 H0 Z-99999
                        G30 P2 X49 Y49 H0 Z-99999
                        G30 P3 X49 Y151 H0 Z-99999 S4

                        but same result, just gives a small judder on first move after running the bed level and then wont move anymore. (Sorry)

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                        • pcsentinelundefined
                          pcsentinel
                          last edited by

                          Update, maybe its just my misunderstanding of how this works, but commented out last line and moved S to third line as

                          G30 P0 X100 Y151 H0 Z-99999
                          G30 P1 X151 Y151 H0 Z-99999
                          G30 P2 X151 Y49 H0 Z-99999 S

                          works and I can then see compensation movement through moves, yet to try with a print though

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                          • dc42undefined
                            dc42 administrators
                            last edited by

                            @pcsentinel:

                            Hi, tried this which is clockwise

                            G30 P0 X151 Y151 H0 Z-99999
                            G30 P1 X151 Y49 H0 Z-99999
                            G30 P2 X49 Y49 H0 Z-99999
                            G30 P3 X49 Y151 H0 Z-99999 S4

                            but same result, just gives a small judder on first move after running the bed level and then wont move anymore. (Sorry)

                            Start with your X49 Y49 point as P0 and go clockwise from there.

                            Duet WiFi hardware designer and firmware engineer
                            Please do not ask me for Duet support via PM or email, use the forum
                            http://www.escher3d.com, https://miscsolutions.wordpress.com

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                            • pcsentinelundefined
                              pcsentinel
                              last edited by

                              Further Update, changed the coords so that there were four but not in a perfect square. And now it works with 4, but following running the bed compensation, Z is set to an insane neagtive number of -199.91

                              G30 P0 X49 Y151 H0 Z-99999
                              G30 P1 X150 Y150 H0 Z-99999
                              G30 P2 X149 Y50 H0 Z-99999
                              G30 P3 X51 Y50 H0 Z-99999 S

                              Go back to 3points as

                              G30 P0 X100 Y151 H0 Z-99999
                              G30 P1 X149 Y50 H0 Z-99999
                              G30 P2 X51 Y50 H0 Z-99999 S

                              and Z after shows 5.73 and z compensation across the bed seems to work, again need to wait till tonight to try a print

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                              • GrodanBundefined
                                GrodanB
                                last edited by

                                Great work, thanks.

                                Just tell me when a beta is available and I test with that.

                                It would be interesting to see the result. I'll switch back to 16 mm square instead of the 32 mm I used for this test.

                                I'll still wonder if there is something hidden in the fact that the measurement clearly shows that the bed is high at the back right off the plate but the print is pressed hard against the plate on precisely that spot… Strange if you ask me...

                                Then I kind of wonder how the compensation is done when printing with dual head. I set the distance between the first tool and the Z-probe. But I do not enter the distant from the second... So is automatically compensated or should I refer to a point in the middle?

                                G31 X-25.19 Y7 Z2.67 P500 ; Set the probe height and threshold; increase Z to decrease bed probe distance X11.0 Y0.5

                                This is relative the tool 1 nozzle... the nozzles are approx. 38 mm apart. So to place the compensation in the middle should I use:

                                G31 X-44.19 Y7 Z2.67 P500

                                Or is the 38mm added due to
                                G10 P1 X38.3 Y0.0 Z0.0 S0 R0

                                So that exact bed leveling is done for the extruding nozzle?

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                                • pcsentinelundefined
                                  pcsentinel
                                  last edited by

                                  Update on G30 four point probing. Now I have actually read DC42's comment (sorry must have overlapped) I have set the four poits clockwise from minor XY as per

                                  G30 P0 X49 Y49 H0 Z-99999
                                  G30 P1 X49 Y149 H0 Z-99999
                                  G30 P2 X149 Y149 H0 Z-99999
                                  G30 P3 X149 Y49 H0 Z-99999 S

                                  it looks like the four pointer is working, the results are
                                  G32
                                  Bed equation fits points [49.0, 49.0, -0.118] [49.0, 149.0, -0.156] [149.0, 149.0, 0.162] [149.0, 49.0, -0.093]

                                  So my final bed.g looks like

                                  ; bed.g
                                  ; called to perform automatic bed compensation via G32
                                  ;
                                  ; generated by RepRapFirmware Configuration Tool on Sun Feb 26 2017 13:25:00 GMT+0000 (GMT Standard Time)
                                  G90
                                  ; Clear any bed transform
                                  M561

                                  ; Probe the bed at 4 points CLOCKWISE!
                                  G28
                                  G30 P0 X49 Y49 H0 Z-99999
                                  G30 P1 X49 Y149 H0 Z-99999
                                  G30 P2 X149 Y149 H0 Z-99999
                                  G30 P3 X149 Y49 H0 Z-99999 S
                                  G1 X0 Y0

                                  Also my Home Z and Home All now have

                                  G1 X1 Y21 F6000
                                  G30

                                  becuase my X offset of the probe from the extruder is 48 and Y offset is 28 and G30 instructions account for the offset in the instructed points.

                                  Hope this helps anyone else who is suffering.

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                                  • pcsentinelundefined
                                    pcsentinel
                                    last edited by

                                    Hi All, can I now confirm that I amprinting the four squares test succesfully. thanks for your help.

                                    DC42 as a suggestion, might it be worthwhile adding the above fledged out with a little explanation to the Wiki, at least for those of us that are using Glass Beds on a Cartesian?

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                                    • deckingmanundefined
                                      deckingman
                                      last edited by

                                      @pcsentinel. Glad you got it sorted. A couple of points. You seem to only be doing the bed compensation for 100mm x 100mm of the bed area. It's usually best to probe close to the 4 extreme corners of the axes movements so that you cover the entire printable area. Also, your Z homing example seems to indicate that you are homing Z at one corner of the bed and it's usually better to do the Z homing at the centre of the bed, because that is where the majority of your printing will take place and therefore where you need the most accuracy. HTH
                                      Ian

                                      Ian
                                      https://somei3deas.wordpress.com/
                                      https://www.youtube.com/@deckingman

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                                      • pcsentinelundefined
                                        pcsentinel
                                        last edited by

                                        Ok, thanks I tried that, but because of my offset when I go to postion 2 on the grid with
                                        G30 P1 X49 Y189 H0 Z-99999
                                        the nozzle is hitting the bed and compressing the carriage before te sensor is activated therefor throwing off the reading

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                                        • dc42undefined
                                          dc42 administrators
                                          last edited by

                                          @pcsentinel:

                                          Ok, thanks I tried that, but because of my offset when I go to postion 2 on the grid with
                                          G30 P1 X49 Y189 H0 Z-99999
                                          the nozzle is hitting the bed and compressing the carriage before te sensor is activated therefor throwing off the reading

                                          I think you must have a severely tilted bed. You can increase the Z probe dive height - it's the H parameter in the M558 command. But it's better to get the bed more level than to rely on a lot of compensation.

                                          Duet WiFi hardware designer and firmware engineer
                                          Please do not ask me for Duet support via PM or email, use the forum
                                          http://www.escher3d.com, https://miscsolutions.wordpress.com

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                                          • GrodanBundefined
                                            GrodanB
                                            last edited by

                                            Is it possible for me to test before a firmware is released?

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