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    Unsolved mesh bed compensation not applying correct corrections

    Tuning and tweaking
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    • necrorat
      necrorat last edited by

      As per the title im having some issues using mesh bed levelling on my new corexy machine.
      I've gone though the setup and configuration of a bltouch sensor following the very good guide on betrue3d site and have the sensor offset and homing of the machine via z probe working perfectly. The issue is when i go to print i run a G29 as part of my start Gcode from cura and it seems that the z motors are applying the wrong correction. consistently the front right is massively over squashed and the top left of my bed the filament is barley touching the build plate. I can see and feel that the motors are correcting but it seems like they are doing the inverse of what they should be doing! also i have checked with M122 that mesh is running and it shows that it is but allying a 0.000mm correction.

      I have rechecked the frame for squareness and that made no difference, I have changed the x gantry as i thought it might of been bowed again no difference and i have trawled thought the firmware but i cant seem to find what could be causing this behaviour.

      Ive tried to get the bottom of this and have spent the better part of two weeks trying to sort it but i cant figure out what is wrong so was hoping someone on here could steer me in the right direction.

      ivae attached my bed.g, config.g homeall.g, homex.g, homex.g and homez.g also my start gcode is as follows:

      ; Startup Gcode
      G91 ; Relative Positioning
      G1 Z-5 ; Move Z down 1mm
      G90 ; Absolute Positioning
      G28 ; Home machine
      G32 ;Check bed level
      G29 ;Run messh leveling
      G29 S1 ; Load hegight map
      G1 X5 Y5 ; Move Head to front left
      G92 E0 ; Zero Extruder
      G1 F200 E20 ; Prime the extruder
      G92 E0 ; Zero Extruder

      homez.g ,homey.g ,homex.g ,homeall.g ,config.g And bed.g

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      • A Former User
        A Former User last edited by

        i could be wrong, but i thought you should only need G28 and G29 S1 if the machine is reliable you'd only need to run that once, not for each print as well

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        • necrorat
          necrorat last edited by

          i tried running just G29 S1 in the start Gcode, same behaviour

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          • Phaedrux
            Phaedrux Moderator last edited by

            Perhaps you need to run G32 a few times to get the bed to level out perfectly?

            Z-Bot CoreXY Build | Thingiverse Profile

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            • necrorat
              necrorat last edited by

              just done a cycle of 5 G32 commands and one after the other and i seem to have a consistent 0.100ish tilt, i do have 2 independent z axis motors could the correction not be applying itself correctly?

              28/01/2020, 00:55:40 G32
              Leadscrew adjustments made: -0.094 -0.111, points used 2, deviation before 0.103 after 0.000
              28/01/2020, 00:55:20 G32
              Leadscrew adjustments made: -0.104 -0.104, points used 2, deviation before 0.104 after 0.000
              28/01/2020, 00:55:01 G32
              Leadscrew adjustments made: -0.101 -0.104, points used 2, deviation before 0.103 after 0.000
              28/01/2020, 00:54:37 G32
              Leadscrew adjustments made: -0.104 -0.102, points used 2, deviation before 0.103 after 0.000
              28/01/2020, 00:54:14 G32
              Leadscrew adjustments made: -0.093 -0.100, points used 2, deviation before 0.097 after 0.000
              28/01/2020, 00:53:53 G32
              Leadscrew adjustments made: -0.122 -0.080, points used 2, deviation before 0.102 after 0.000

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              • Phaedrux
                Phaedrux Moderator last edited by

                I'm not sure what to make of those results.

                Z-Bot CoreXY Build | Thingiverse Profile

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                • SIam
                  SIam last edited by SIam

                  M671 x-60:353 Y140:140 S2                ; leadscrew at left (connected to z) and right (connected to
                  

                  are you shure that your first leadscrew is on pos x-60 y 140
                  and the second is on x353 y140 ???

                  if yes than the limits are wrong

                  ; Axis Limits
                  M208 X0 Y0 Z-1 S1                        ; set axis minima
                  M208 X295 Y277 Z275 S0
                  

                  for example my working config with 3 leadscrews:

                  M671 X0:380:0 Y52:190:327 S3 F1.0; Leitspindeln links und rechts von der X-Achse
                  

                  Hypercube-Evolution-Hybrid, Piezo Orion, Orbiter
                  Duet WiFi 1.02 or later + DueX5
                  RepRapFirmware for Duet 2 WiFi/Ethernet 3.4.0beta4 (2021-09-27 11:30:36)
                  Duet WiFi Server: 1.26
                  Duet Web Control 3.4.0beta4 (2021-09-27)

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                  • necrorat
                    necrorat last edited by necrorat

                    so the stated points are from the machine origin ie 00 the left leadscrew is to the left of the heat bed and the right leadscrew is to the right of the heat bed so the machine cant physically reach those points. should the m208 also have these figures in?

                    Phaedrux 1 Reply Last reply Reply Quote 0
                    • Phaedrux
                      Phaedrux Moderator @necrorat last edited by

                      @necrorat said in mesh bed compensation not applying correct corrections:

                      should the m208 also have these figures in?

                      No, M208 should define your reachable area. It's normal for the lead screws to be outside the print area. Your probe points should be as close as possible to the lead screws.

                      Z-Bot CoreXY Build | Thingiverse Profile

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                      • Veti
                        Veti last edited by

                        i dont think there should be a G29 S1 in the bed.g

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                        • Veti
                          Veti last edited by

                          M557 X23:270 Y9:265 P2 ; define mesh grid

                          P2 will not result in a usable mesh.

                          try S15

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                          • necrorat
                            necrorat last edited by necrorat

                            for the p parameter it was originally at 8 and behaved exactly the same. i am using two now to speed up iterations and to see if there is an improvement, so far the exactly the same behaviour despite the amount of probed points. as for the bed.g ill remove the G29 and see if that helps

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                            • necrorat
                              necrorat @Phaedrux last edited by

                              @Phaedrux that was my understanding and have set them as such. the probe point is about 10mm in from the edge of the bed so as close as reasonably possible

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                              • necrorat
                                necrorat last edited by necrorat

                                one further question when taking the measurements for the where the leadscrews are positioned should i be taking the measurements from the nozzle or from the probe? (nozzle is 0,0)

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                                • Phaedrux
                                  Phaedrux Moderator last edited by

                                  I'm not sure I understand what you mean. The lead screws are fixed in relation to the bed, so their position is absolute. 0,0 is a point on the bed, the nozzle/probe/printhead is relative to that. The lead screw position would be relative to the 0,0 position in absolute coordinates.

                                  Does that make sense?

                                  Z-Bot CoreXY Build | Thingiverse Profile

                                  necrorat 1 Reply Last reply Reply Quote 0
                                  • necrorat
                                    necrorat @Phaedrux last edited by

                                    @Phaedrux so when i home my machine the print head moves to 0,0 which lines up with the printer nozzle being in the bottom left corner. what i wanted to check is that the bed compensation calculations where been done relative to the nozzle not the probe as the probe is offset approximately 23mm from the nozzle. so the above values would of been off but after digging and as you said the calcs are done from the nozzle for all intensive purposes and that is how i have it configured at the moment.

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                                    • necrorat
                                      necrorat last edited by

                                      so an update to the issue. spent all of this evening re checking that the machine is as square as reasonably possible and have levelled the bed to as close as i can get it to perfectly flat

                                      height map.png
                                      but now when i go to load up the height map it gives me the error:
                                      G29 S1
                                      Error: G29: Failed to load height map from file heightmap.csv: failed to read line from file

                                      at this point i dont really need mesh compensation as get ting very nice first layers without the mesh but for completions sake i want to get everything working as intended and iron out the few areas that are slightly more squashed than others on the first layer. should i try reducing the number of probed points to try and get it to accept the height map? or just any steers in the right direction would be highly appreciated.

                                      Phaedrux 1 Reply Last reply Reply Quote 0
                                      • Phaedrux
                                        Phaedrux Moderator last edited by

                                        Can you upload that Height map. CSV?

                                        Z-Bot CoreXY Build | Thingiverse Profile

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                                        • necrorat
                                          necrorat @Phaedrux last edited by

                                          @Phaedrux heightmap.csv there you go mate, appreciate the help so far!

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                                          • Phaedrux
                                            Phaedrux Moderator last edited by

                                            I don't see anything in particular wrong with that file. Try deleting it from the SD card and re-running G29

                                            Z-Bot CoreXY Build | Thingiverse Profile

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                                            • necrorat
                                              necrorat last edited by

                                              so deleted the file and reduced the number of probe points and it seems to of accepted the file now,but it still seems to be not applying the mesh correctly. there are inconstant very small gaps between the extruded lines in a couple of patches on the bed so that leads me to believe that something i have borked up in my config. ive checked my extrusion multiplier and calibrated my e steps so at this stage it must be something in my config or associated files.

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                                              • Veti
                                                Veti last edited by

                                                @necrorat said in mesh bed compensation not applying correct corrections:

                                                inconstant very small gaps between the extruded lines in a couple of patches on the bed

                                                that is either a problem with under extrusion or backlash in your printer. not a problem with mesh bed leveling.

                                                necrorat 1 Reply Last reply Reply Quote 0
                                                • necrorat
                                                  necrorat @Veti last edited by necrorat

                                                  @Veti 90% of the bed layer is perfect there are two patches where the gaps are observed so if it was under extrusion or backlash would it not be consistently like that all over the bed with mesh levelling working as it should?

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                                                  • Veti
                                                    Veti last edited by

                                                    post a picture

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                                                    • Phaedrux
                                                      Phaedrux Moderator @necrorat last edited by

                                                      @necrorat said in mesh bed compensation not applying correct corrections:

                                                      height map.png

                                                      The image seems to show a bowed gantry. What areas are not touching the bed?

                                                      Z-Bot CoreXY Build | Thingiverse Profile

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