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    Auto bed compensation questions and issues

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    • Gaz6
      Gaz6 last edited by

      Hey,
      I am new to Duet and trying to figure out how to work with the board correctly.
      I think that my bed compensation is not working at all. I don't feel or see the screws rotate at all during XY movement. The Z axis moves without any issue(even if I connect the 4 motors to the same driver)
      Also, when I use babysteps the bed will not move during a layer change. Not in the printer and not in the web interface. I just see the same value as the first layer after the babysteps.
      Can it be connected to the 4 motors on 1 driver? It is moving pretty smooth and the driver is not hot.

      Another question is regarding the Z probe offset, I am using an inductive sensor and I could not find information on how to adjust it right. What does (-) and (+) mean? What is my point of reference?

      I have a cartesian machine with Duet2 wifi (1.02 or later) Firmware:2.01(RTOS) (2018-07-26b2)
      0_1557051353291_config.g

      Thank you for your help

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      • Veti
        Veti last edited by

        what stepper motors do you have?

        12v or 24v?

        are the 4 motors in series or parallel?

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        • Gaz6
          Gaz6 last edited by

          I am using NEMA 17, 24 volts.
          I have two cables for the Z motors, each connects on one side to 2 motors and on the other side to the Duet. The cables are connecting the motors in parallel. I don't know how the duet dual Z connectors work...

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          • Veti
            Veti last edited by

            @gaz6 said in Auto bed compensation questions and issues:

            NEMA 17

            there are many different nema 17 stepper motors. please post the specific data on your steppers.

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            • Gaz6
              Gaz6 last edited by

              It is Motech motors and the datasheet is located here: http://motechmotor.com/productDetail-0104-32.html.

              The motors were able to move the bed without any problem and I have now finished printing a 400 mm tall cube but my first layer looks bad and my brim did not adhere at all.
              I don't see the connection to the motor type as before I moved to Duet I was printing with the same setup using MKS gen board and Marlin 1.9 UBL activated.
              Why do you think it is related to the motors?

              Thank you

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              • Veti
                Veti last edited by

                you have 1.68A motors
                However if you connect 4 motors in parallel you run them at 1/4 the current.

                You configured 0.8A.

                So thats 0.2A per motor.
                not even 25%.

                The connectors on the duet run them in series.
                so start of by connecting 2 to each port.
                Then increase your current.
                You want to run your motors at 75% of their rated current, but that might be pushing it on the duet drivers.

                zapta 1 Reply Last reply Reply Quote 0
                • Gaz6
                  Gaz6 last edited by

                  Ok. I understand.
                  I tried what you suggested and nothing changed. I still don't see the bed compensation in work.
                  I then connected 2 motors to E1 driver and the same result. There is no compensation at all.
                  In all senarios, I was able to probe the bed, move the bed all the way down and all the way up.
                  When I press the Auto Bed compensation I can see the bed topography.
                  What am I missing?

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                  • Phaedrux
                    Phaedrux Moderator last edited by

                    are you enabling the compensation at some point before the print?
                    G29 S1 will load a saved heightmap. That needs to go into your slicer start gcode to enable it before a print.

                    If you run M122 during a print, does it show compensation as "mesh" ?

                    You may also want to update your firmware to 2.02.

                    Z-Bot CoreXY Build | Thingiverse Profile

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                    • Gaz6
                      Gaz6 last edited by

                      @phaedrux said in Auto bed compensation questions and issues:

                      compensation

                      I updated the firmware. I have added the G29 S1 to the GCODE after the G28 command.
                      I don't see 'compensation' or 'mesh' in the M122
                      0_1557126505840_M122.txt

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                      • Phaedrux
                        Phaedrux Moderator last edited by

                        Looks like it is being loaded.

                        Bed compensation in use: mesh

                        Z-Bot CoreXY Build | Thingiverse Profile

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                        • zapta
                          zapta @Veti last edited by

                          @veti said in Auto bed compensation questions and issues:

                          However if you connect 4 motors in parallel you run them at 1/4 the current.

                          From the description above it seems that the steppers are connected as 2P2S and thus each sees 1/2 of the current.

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                          • Gaz6
                            Gaz6 last edited by

                            @phaedrux said in Auto bed compensation questions and issues:

                            M122

                            I started from scratch and now the compensation is working...

                            Regarding G31 command... What is the difference between the P and the Z? How do I work with those values for an inductive sensor?

                            How do I set the offset values of the probe relative to the nozzle? Do I use minus values? I know I use G31 with X and Y values but how to set them relative to my nozzle?

                            dc42 1 Reply Last reply Reply Quote 0
                            • dc42
                              dc42 administrators @Gaz6 last edited by

                              @gaz6 said in Auto bed compensation questions and issues:

                              Regarding G31 command... What is the difference between the P and the Z? How do I work with those values for an inductive sensor?

                              Z is the trigger height. For an inductive sensor it should be positive (sensor triggers before the nozzle touches the bed).

                              P is trigger level, and only makes much difference if you are using a sensor with an analog output.

                              How do I set the offset values of the probe relative to the nozzle? Do I use minus values? I know I use G31 with X and Y values but how to set them relative to my nozzle?

                              The X and Y parameters in G31 are the offsets of the probe from the head reference point (HRP). In single-extrusion printers, the HRP is normally the nozzle. So use positive values if the probe offsets are in the +X and +Y directions from the nozzle.

                              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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                              • Gaz6
                                Gaz6 last edited by

                                Ok, thank you.

                                When I add the probe offset the printer won't probe a lot of points that my probe can reach. My inductive sensor is located inside the bed during all movement of the printer.
                                My last probing point is the bed size minus the probe offset values. I would like to be able to probe from edge to edge. Is it possible?

                                In Marlin, you have an interpolation command to estimate the points the probe can't reach. Does duet have it as well?

                                Thank you for all the help!

                                Phaedrux dc42 2 Replies Last reply Reply Quote 0
                                • Phaedrux
                                  Phaedrux Moderator @Gaz6 last edited by

                                  @gaz6 RRF will automatically interpolate for the area it can't reach.

                                  Z-Bot CoreXY Build | Thingiverse Profile

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                                  • dc42
                                    dc42 administrators @Gaz6 last edited by

                                    @gaz6 said in Auto bed compensation questions and issues:

                                    My last probing point is the bed size minus the probe offset values. I would like to be able to probe from edge to edge. Is it possible?

                                    In your M557 command, specify the coordinates that you want to probe. Do not correct them for probe offset. The firmware will place the nozzle at the correct point so that the probe is where you asked to probe, allowing for the nozzle offset. So you can probe anywhere that the probe can reach, assuming you have set the M208 limits correctly. For example, if your probe is offset by +30mm in the X direction, and the lowest X coordinate you want to probe is X10, then the firmware will move the head to X-20 to do that - assuming that the lower X limit set by M208 is -20 or lower.

                                    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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                                    • Gaz6
                                      Gaz6 last edited by

                                      Thank you.
                                      I have just done that.
                                      I had to add G92 X0 to my homeall and xhome files after homing is finished so I won't have -30 in my X position after homing. Any other solution to that?

                                      dc42 1 Reply Last reply Reply Quote 0
                                      • Phaedrux
                                        Phaedrux Moderator last edited by

                                        Well you may actually want to have that -30 in your X position if the nozzle is actually 30mm away from the edge of the bed.

                                        Z-Bot CoreXY Build | Thingiverse Profile

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                                        • dc42
                                          dc42 administrators @Gaz6 last edited by dc42

                                          @gaz6 said in Auto bed compensation questions and issues:

                                          I had to add G92 X0 to my homeall and xhome files after homing is finished so I won't have -30 in my X position after homing. Any other solution to that?

                                          If your printer homes X with the nozzle 30mm off the left edge of the bed, then it's right that the X position is -30 immediately after homing X, assuming that you want X=0 to correspond to the left edge of the bed. [Another common choice is to make X=0 Y=0 the centre of the bed.]

                                          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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