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    Scanning Z probe support in RRF 3.5

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    • CNCModellerundefined
      CNCModeller @dc42
      last edited by

      @dc42 I'm using the type that looks like flexible rubber fridge magnets so we'll see how that compares. The flux is in long lines spaced at about 10mm pitch.

      Polar Duet3 Mini + 1HCL
      https://youtube.com/playlist?list=PLWjZVEdMv1BY82izahK45qKh-hp3NFkix
      Wanhao D4S: Duet2
      https://forum.duet3d.com/post/296755
      K40 Laser, Duet2
      https://forum.duet3d.com/post/312082
      Wanhao D5S
      https://www.youtube.com/CNCModellerUK

      1 Reply Last reply Reply Quote 1
      • T3P3Tonyundefined
        T3P3Tony administrators @dc42
        last edited by

        That mandalaroseworks bed does have pretty darn strong magnets in it!

        @dc42 why not do a bed scan without the flex sheet installed just for comparison.

        www.duet3d.com

        dc42undefined 1 Reply Last reply Reply Quote 0
        • dc42undefined
          dc42 administrators @T3P3Tony
          last edited by

          @T3P3Tony OK, here it is.

          ec98784f-9ad0-427d-90c9-8e41fdf92347-image.png

          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

          T3P3Tonyundefined dc42undefined 2 Replies Last reply Reply Quote 0
          • T3P3Tonyundefined
            T3P3Tony administrators @dc42
            last edited by

            @dc42 cool, you can clearly see the magnets!

            One other interesting test would be to put a thin shim in the middle under the flexi build plate (say a couple of M4 washers and see how accurately it picks up the deformation of the flex plate.

            www.duet3d.com

            dc42undefined 1 Reply Last reply Reply Quote 0
            • dc42undefined
              dc42 administrators @dc42
              last edited by

              Here's the scan with the bed plate, for comparison. It looks to me that the magnets are being picked up very slightly.

              241c9a19-4371-49d5-a1d7-4a88e2cf2814-image.png

              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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              • dc42undefined
                dc42 administrators @T3P3Tony
                last edited by dc42

                @T3P3Tony as you wish:

                e9a561d8-49ea-4644-893b-e35abf1a5d71-image.png

                One 0.8mm M4 washer in each of two locations.

                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

                T3P3Tonyundefined 1 Reply Last reply Reply Quote 1
                • T3P3Tonyundefined
                  T3P3Tony administrators @dc42
                  last edited by

                  @dc42 definitively confirms its picking up the flex plate and not the underlying bed/magnets

                  www.duet3d.com

                  CNCModellerundefined 1 Reply Last reply Reply Quote 0
                  • CNCModellerundefined
                    CNCModeller @T3P3Tony
                    last edited by CNCModeller

                    @T3P3Tony @dc42

                    1688386589765217860994438101262.jpg

                    This is what the field lines on the magnetic build plate I'm using looks like, zoom into the magnetic detection film.

                    It's stuck to a 4mm thick mirror on top of a 4mm thick aluminium plate which has the 250v heater pad on the back of it.

                    It'll be interesting to see if the AC bed makes a difference when it's on. I guess I should be able to turn it off for the scan once the bed is up to temperature.

                    I'm assuming the inductive probe will pick up on the mirror coating if it doesn't interact with the rubberised magnetic build sheet.

                    It'll be a while before I can test this as I've got a lot on at the moment but everything is in hand to give it a try.

                    For the record very impressed on how quickly this has been done, as always the Duet3D team is top banana 🍌 πŸ‘

                    All the best
                    Barry M

                    Polar Duet3 Mini + 1HCL
                    https://youtube.com/playlist?list=PLWjZVEdMv1BY82izahK45qKh-hp3NFkix
                    Wanhao D4S: Duet2
                    https://forum.duet3d.com/post/296755
                    K40 Laser, Duet2
                    https://forum.duet3d.com/post/312082
                    Wanhao D5S
                    https://www.youtube.com/CNCModellerUK

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                    • o_lampeundefined
                      o_lampe @dc42
                      last edited by

                      @dc42 These stronger magnetic sheets have alternating magnet orientation. (just mentioning it, not everyone knows)
                      It probably depends if you scan along the magnet lines or cross them.

                      CNCModellerundefined 1 Reply Last reply Reply Quote 0
                      • CNCModellerundefined
                        CNCModeller @o_lampe
                        last edited by

                        ... and even when in line with the field lines the pitch of the scan might need to be the same as or multiples of the pitch of the field lines. And that assumes every field line is the same strength.

                        Will be an interesting experiment none the less...

                        Polar Duet3 Mini + 1HCL
                        https://youtube.com/playlist?list=PLWjZVEdMv1BY82izahK45qKh-hp3NFkix
                        Wanhao D4S: Duet2
                        https://forum.duet3d.com/post/296755
                        K40 Laser, Duet2
                        https://forum.duet3d.com/post/312082
                        Wanhao D5S
                        https://www.youtube.com/CNCModellerUK

                        dc42undefined 1 Reply Last reply Reply Quote 0
                        • dc42undefined
                          dc42 administrators @CNCModeller
                          last edited by

                          @CNCModeller I don't think the static magnetic field should affect the sensor significantly, because it's unlikely to cause magnetic saturation.

                          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

                          dc42undefined 1 Reply Last reply Reply Quote 0
                          • dc42undefined
                            dc42 administrators @dc42
                            last edited by dc42

                            I've made some further improvements to the scanning probe software:

                            • Previously I was fitting the sensor frequency vs. height calibration points to a quadratic curve. When I plotted the residual in a spreadsheet I saw that there was a small cubic residual error. Now I fit a cubic curve to the points instead.
                            • I hadn't noticed that during calibration, when the sensor got close to the bed it returned an amplitude error, which affected the calibration. I have increased the oscillation amplitude to fix this.

                            Here is a 522 point height map produced by the scanning sensor in 21 seconds, including the time taken to do a regular probe at bed centre (to establish an accurate Z=0 datum) and then calibrate the scanning probe:

                            466c0e3f-4f23-4686-b5d4-1354e48b54ea-image.png

                            Here is a height map of the same bed produced using the microswitch probe in 5 min 28 seconds (I reduced the dive height to 2mm to speed up probing):

                            983b9d47-60c5-41be-8762-1c74e71040e6-image.png

                            There's not much difference between them, except for a 0.04mm offset that I need to track down.

                            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

                            samlogan87undefined o_lampeundefined 2 Replies Last reply Reply Quote 2
                            • samlogan87undefined
                              samlogan87 @dc42
                              last edited by

                              @dc42 when you did that, was the bed warm or are you still playing around with it when it’s cold?

                              Custom Core-XY

                              dc42undefined 1 Reply Last reply Reply Quote 0
                              • dc42undefined
                                dc42 administrators @samlogan87
                                last edited by

                                @samlogan87 it's still cold. I'll try heating the bed to 80C next.

                                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

                                samlogan87undefined 1 Reply Last reply Reply Quote 0
                                • o_lampeundefined
                                  o_lampe @dc42
                                  last edited by

                                  @dc42 said in Scanning Z probe support in RRF 3.5:

                                  There's not much difference between them

                                  The max. deviation numbers have a huge difference:
                                  -0.351 vs -0.198
                                  That's almost a layer thickness, or am I wrong?

                                  dc42undefined 1 Reply Last reply Reply Quote 0
                                  • samlogan87undefined
                                    samlogan87 @dc42
                                    last edited by

                                    @dc42 cool. It is looking very promising though. Awesome work. I have a 400x400mm bed and always have issues with bed flatness especially when you really heat it up to do nylons etc

                                    Custom Core-XY

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                                    • dc42undefined
                                      dc42 administrators @o_lampe
                                      last edited by dc42

                                      @o_lampe said in Scanning Z probe support in RRF 3.5:

                                      The max. deviation numbers have a huge difference:
                                      -0.351 vs -0.198
                                      That's almost a layer thickness, or am I wrong?

                                      Those most negative height error values are in the mid right hand edge of the map. 0.04mm of the difference is accounted for by the offset between the height maps. I think the remainder is caused by the bed magnet at that position. It's now clear to me that the six bed magnets are causing slight dips in the height map produced by the scanning probe. This is especially clear along the left hand edge.

                                      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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                                      • lparnell34undefined
                                        lparnell34
                                        last edited by lparnell34

                                        Im getting a G31: invalid z probe index error and also Error: M558: Unknown pin name 'i2c.ldc1612'
                                        I modified my config.g and mesh.g to include your changes. Im using the sammyc21 expansion board.

                                        I'm also using the latest firmware that I built for the sammyc21 and duet3 6hc from github today.

                                        dc42undefined 1 Reply Last reply Reply Quote 0
                                        • dc42undefined
                                          dc42 administrators @lparnell34
                                          last edited by

                                          @lparnell34 sounds like you must have built RRF using the wrong branches from Github. Use the 3.5-dev branches.

                                          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

                                          lparnell34undefined 1 Reply Last reply Reply Quote 0
                                          • lparnell34undefined
                                            lparnell34 @dc42
                                            last edited by

                                            @dc42 I used the 3.5 dev builds.

                                            dc42undefined 2 Replies Last reply Reply Quote 0
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