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    Mesh Bed Compensation not compensating?

    Scheduled Pinned Locked Moved
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    • timcurtis67undefined
      timcurtis67 @cemejean
      last edited by

      @cemejean said in Mesh Bed Compensation not compensating?:

      @Argo I believe that your Z axis minimum limit needs to be a negative value.

      https://forum.duet3d.com/topic/16185/mesh-bed-leveling-not-moving-bed/2

      +1

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      • Argoundefined
        Argo
        last edited by

        I think those limits are only for gcode commands and not for the firmware itself.
        But I'll test it anyway.

        Phaedruxundefined 1 Reply Last reply Reply Quote 1
        • Argoundefined
          Argo
          last edited by

          I just tested it with "M208 X0:250 Y0:210 Z-2:205"

          The effect is the same. After G29 I can travel to the right and see a 0.1-0.2mm gap when there should be Z=0.

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          • Phaedruxundefined
            Phaedrux Moderator
            last edited by

            Is there anything mechanically pulling at the print head when in that position?

            Does your BLtouch mount have some tilt to it?

            What do you have in bed.g for your tilt correction?

            Also please post your homeall.g

            Are you doing a G29 before each print?

            You can increase the accuracy of the BLtouch with some slight changes to your M558 and G31

            M558 P9 C"^zprobe.in" H5 F120 T12000 A10 S0.005
            G31 P25 X30.6 Y-12.0 Z2.315
            

            Note this will make your initial dive speed much slower. You can modify your homeall to set a faster speed for the first probe and then do a slower detailed probe

            M558 F500 A1 ; probe once quickly
            G30
            M558 F120 A10 ; detailed probe
            G30
            

            Z-Bot CoreXY Build | Thingiverse Profile

            Argoundefined 1 Reply Last reply Reply Quote 0
            • Phaedruxundefined
              Phaedrux Moderator @Argo
              last edited by

              @Argo said in Mesh Bed Compensation not compensating?:

              I think those limits are only for gcode commands and not for the firmware itself.
              But I'll test it anyway.

              That's correct. The firmware will be able to compensate below the 0 point provided it is physically able to do so. For baby stepping purposes it can be useful to have a slightly negative value for the Z minima because by default you're only able to move down an amount equal to the thickness of the first layer height.

              Z-Bot CoreXY Build | Thingiverse Profile

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              • RyanPundefined
                RyanP
                last edited by RyanP

                I find the same thing on my E5Plus. Even thought I do a fairly long and detailed bed process, I still find that I am having to babystep my way out of a disaster with most prints. Or worse, have to adjust the bed knobs. My regular ender5 and the CR10S (all running duets) don't seem to have this problem on such a consistent basis.

                I even switched the setup to independant z motors and perform a G32, and still find I have to watch the first layer and make sure the filament goes down properly.

                I perform a G28 to start, then a G32 to level the separate z axis, then do a G29 for the mesh. Still have issues. So either the G32 undoes itself, or it needs to be done after the G29...which does not make any sense.

                CR10S, August 2018
                Anycubic Photon S December 2019
                Ender 5 Feb 2020
                Ender 5 Plus May 2020
                Anycubic Photon Mono X Nov 2020
                ~
                https://3dimensiongames.com/

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

                  @RyanP said in Mesh Bed Compensation not compensating?:

                  I perform a G28 to start, then a G32 to level the separate z axis, then do a G29 for the mesh. Still have issues. So either the G32 undoes itself, or it needs to be done after the G29...which does not make any sense.

                  You may need to do the G32 a few times over, and you should do a single G30 at the center of the bed afterwards to redefine the Z0. Then the G29.

                  Z-Bot CoreXY Build | Thingiverse Profile

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                  • Argoundefined
                    Argo @Phaedrux
                    last edited by

                    @Phaedrux

                    I don't think the BLTouch mount has tilt but the pin looks slightly bend to the right.
                    I temporarily disabled G32 in my start gcode and calibrated my axis by running against the Z endstops.
                    Afterwards I did G29 mesh leveling and the result was a severe tilted bed (right side was higher).
                    I suspect now that is has something to do with the BLTouch. Next thing I'll do is to replace the PIN and also print another more stable mount.

                    For completion:

                    homeall.g

                    ; homeall.g
                    ; called to home all axes
                    ;
                    ; generated by RepRapFirmware Configuration Tool v2 on Tue Aug 06 2019 23:15:45 GMT+0200 (Central European Summer Time)
                    G91                     ; relative positioning
                    M915 X S-6 F0 H400 R0		                ; Set X axis Sensitivity
                    M915 Y S-1 F0 H400 R0		                ; Set y axis Sensitivity
                    G1 Z6 F6000 H2          ; lift Z relative to current position
                    G1 H1 X-255 F2600 ; move quickly to X and Y axis endstops and stop there (first pass)
                    G1 H1 Y-215 F2600 ; move quickly to X and Y axis endstops and stop there (first pass)
                    G1 X5 Y5 F6000          ; go back a few mm
                    G1 H1 X-255 F2600  ; move slowly to X and Y axis endstops once more (second pass)
                    G1 H1 Y-215 F2600  ; move slowly to X and Y axis endstops once more (second pass)
                    G90                     ; absolute positioning
                    G1 X15 Y15 F6000        ; go to first bed probe point and home Z
                    G30                     ; home Z by probing the bed
                    
                    M915 X S3 F0 H400 R1		                ; Set X axis Sensitivity
                    M915 Y S3 F0 H400 R1		                ; Set y axis Sensitivity
                    

                    bed.g

                    ; bed.g
                    ; called to perform automatic bed compensation via G32
                    
                    
                    M561 ; clear any bed transform
                    G28 W ; home
                    G30 P0 X35 Y100 Z-99999 ; probe near a leadscrew, half way along Y axis
                    G30 P1 X240 Y100 Z-99999 S2 ; probe near a leadscrew and calibrate 2 motors
                    
                    
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                    • Argoundefined
                      Argo
                      last edited by

                      I just replaced the X axis rods (one was slightly bend) and printed another BL Touch mount and replaced the pin.
                      Just as before the nozzle is too far away on the right side of the bed which results in the line not sticking together.

                      Height Map:
                      BED.png

                      Print result (middle and right tile):
                      results.jpg

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                      • Phaedruxundefined
                        Phaedrux Moderator
                        last edited by

                        Is there some skew in the bed rail?

                        G1 X15 Y15 F6000 ; go to first bed probe point and home Z
                        G30 ; home Z by probing the bed

                        Also may want to move the probe point to the center of the bed.

                        Z-Bot CoreXY Build | Thingiverse Profile

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                        • RyanPundefined
                          RyanP
                          last edited by

                          @Argo

                          You and I are experiencing the same thing, with the same brand (and model) of printer. Have you printed anything else? Like a simple box. Something with a flat surface. I print a lot of simple boxes for board games. The tend to have a number of flat solid layers. Picture a box with a open top, and solid bottom.

                          My layers tend to have this double line, gap, double line, gap. Just like your right hand square. I am starting to think it is a mechanical problem with Creality printers. I have three of them and this patters happens on them all. It isnt on every part, or in every area. I think a lot of it is based on the BL Touch in conjunction with a backlash or mechanical shifting of things in the X-Axis or Y-Axis.

                          I am currently printing a fairly intricate player box for the board game Scythe. When it is done, I will post a picture of its flat surfaces.

                          Keep me in the loop as to your findings as I am working through various solutions myself.

                          CR10S, August 2018
                          Anycubic Photon S December 2019
                          Ender 5 Feb 2020
                          Ender 5 Plus May 2020
                          Anycubic Photon Mono X Nov 2020
                          ~
                          https://3dimensiongames.com/

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

                            @Phaedrux

                            Sorry for not mentioning that I‘m already using your advice to probe with 0.005 accuracy and after G32 I probe the center to determine Z=0.

                            New observation: after leveling the bed with a crazy 12x12 grid I can see that there is something wrong with the bad. It is very bumpy and when I print with the 12x12 mesh my Z axis can’t keep up and I have small hiccups during fast travel moves.

                            Next thing I do is to disassemble the Y axis, check the rods and the Y carriage for their flatness.
                            Hopefully I don’t have to order both.

                            Crazy that so many thing all at once tend to break 😞

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                            • Argoundefined
                              Argo @RyanP
                              last edited by

                              @RyanP

                              I’m having a MK3s Prusa printer.
                              The lines got better but only with crazy accurate 12x12 mesh bed compensation. I suspect there is something terrible wrong with my y axis rods, bed or carriage or worst case: all at once.

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                              • Argoundefined
                                Argo
                                last edited by

                                Update:

                                Y-Axis rods and the bed look fine.
                                I just leveld my x axis (tilt) by slowly driving the x-axis against the Z endstops.

                                New height map (7x7 mesh leveling, with center Z probe and 0.005 accuracy):
                                Screenshot 2020-05-22 at 14.47.32 .png

                                Print picture is the same. Left side is too close, right side too far away.

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                                • Phaedruxundefined
                                  Phaedrux Moderator @Argo
                                  last edited by

                                  @Argo said in Mesh Bed Compensation not compensating?:

                                  t is very bumpy and when I print with the 12x12 mesh my Z axis can’t keep up and I have small hiccups during fast travel moves.

                                  Increase your Z jerk. M566 Z24.00 is very low. Try at least 60. That should solve the stutters.

                                  Z-Bot CoreXY Build | Thingiverse Profile

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                                  • shirnschallundefined
                                    shirnschall
                                    last edited by

                                    I recently had a similar issue and the problem was that the z screw was turning but the nozzle was not moving accordingly.

                                    1. Check if your Z leadscrews are turning when moving the nozzle from left to right (using gcode. Not by hand)

                                    2. if the screws are turning check if there is any slop in the system. If possible measure how much the nozzle moves up and down

                                    If the z screws are not turning it I would suspect a problem with the probing itself

                                    My printer: DIY 2020 extrusion CoreXY with E3D Tool-changing and Duet3 (https://github.com/shirnschall/HS-Bot-Project)

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                                    • Argoundefined
                                      Argo
                                      last edited by

                                      I did a complete frame rebuild today which improved things but it’s still not perfect level. There are parts on the bed which are good and parts which aren’t.
                                      I’d say the inaccuracy between perfect layer and what the BLTouch measures at some spots is around 0.020mm to 0.025mm.

                                      I suspect the BLTouch measuring error comes from the fact that it is mounted too far away from the nozzle. The Y offset is -12mm from nozzle and the mount I’m using atm has even higher offset from Y.
                                      Thereby every small inconsistency in printed parts gets magnified by the position from the BLTouch, it’s like a lever.

                                      My extruder has a slot for the Prusa PINDA Mount which merely has an offset of 2mm on the y axis.
                                      I’ll try to configure it today and see if that helps.
                                      I never did so because only RRF 3 supports the probe’s thermistor.

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                                      • Argoundefined
                                        Argo
                                        last edited by Argo

                                        Do give you guys an update and also for someone who might have the same issue:

                                        Installing the probe (in my case PINDA 2) with almost no Y offset solved my probing problem.
                                        My guess ist that any small difference (parts, rods, frame) gets amplified by the probe when the location has a big Y offset to the nozzle.

                                        I also do not recommend using "True Bed Leveling" with a cartesian printer. This could tilt the X axis which does also add an angle to the nozzle and probe. I level my X axis (tilt) by running into the Z endstops.

                                        New working height map (almost perfect first layer)

                                        940fd036-216c-468b-a433-e59edf074eed-image.png

                                        Z = 0 reference point is X10 / Y10.

                                        And if anyone is interested in how in configured my PINDA:

                                        ; Z-Probe PINDA
                                        M574 Z1 S2 ; Set endstops controlled by probe
                                        M558 P5 C"^zprobe.in" I1 H0.9 F1000 T6000 A20 S0.005 ; PINDA
                                        G31 P1000 X23 Y5 Z1.025 ; PEI Sheet Offset
                                        ;G31 P1000 X23 Y5 Z1.325 ; Textured Sheet Offset
                                        M557 X24:221 Y10:195 P12 ; Define mesh grid

                                        The probing is quite fast but the accuracy is quite good as the probe rarely needs more than 2 probes per point.
                                        Next I need to figure out how to use the temperature compensation with the G31 command.

                                        fcwiltundefined 1 Reply Last reply Reply Quote 1
                                        • fcwiltundefined
                                          fcwilt @Argo
                                          last edited by

                                          @Argo

                                          If you run the probing multiple times are the results fairly consistent?

                                          Thanks.

                                          Frederick

                                          Printers: a small Utilmaker style, a small CoreXY and a E3D MS/TC setup. Various hotends. Using Duet 3 hardware running 3.4.6

                                          Argoundefined 1 Reply Last reply Reply Quote 0
                                          • Argoundefined
                                            Argo @fcwilt
                                            last edited by Argo

                                            @fcwilt

                                            Yes they are but not the overall Z offest because of the rising temperature of the probe.

                                            fcwiltundefined 1 Reply Last reply Reply Quote 0
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