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    Scanning Z probe support in RRF 3.5

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    • CNCModellerundefined
      CNCModeller
      last edited by CNCModeller

      @dc42 is it fair to say that this type of probe wouldn't be much use scanning a flexible magnetic build sheet like this ? Due to the varying magnetic field?

      Polar Duet3 Mini + 1HCL
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      dc42undefined 1 Reply Last reply Reply Quote 0
      • dc42undefined
        dc42 administrators @CNCModeller
        last edited by

        @CNCModeller I am using the probe with a flexible magnetic sheet. I was expecting the magnets underneath it to show up in the height map, but they don't. However, the instructions for the Beacon probe say you need to avoid strong magnets.

        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

        CNCModellerundefined o_lampeundefined 2 Replies Last reply Reply Quote 0
        • CNCModellerundefined
          CNCModeller @dc42
          last edited by

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

          @CNCModeller I am using the probe with a flexible magnetic sheet. I was expecting the magnets underneath it to show up in the height map, but they don't. However, the instructions for the Beacon probe say you need to avoid strong magnets.

          @dc42 In your experience, does the height map reference to the magnetic sheet surface or the underlying metal bed?

          Polar Duet3 Mini + 1HCL
          https://youtube.com/playlist?list=PLWjZVEdMv1BY82izahK45qKh-hp3NFkix
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          dc42undefined 1 Reply Last reply Reply Quote 0
          • dc42undefined
            dc42 administrators @CNCModeller
            last edited by dc42

            @CNCModeller I can's say because I don't use one without the other. However, the fact that the probe doesn't see the magnets suggests to me that it is sensing the sheet.

            For reference I am using this bed https://mandalaroseworks.com/products/magbed-for-e3d-toolchanger and this sheet https://whambam3d.com/collections/build-surfaces/products/flexi-plate-with-pre-installed-pex-build-surface?variant=39372386566242.

            Duet WiFi hardware designer and firmware engineer
            Please do not ask me for Duet support via PM or email, use the forum
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            CNCModellerundefined T3P3Tonyundefined 2 Replies Last reply Reply Quote 0
            • 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
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              • 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
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                  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
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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
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                        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
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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
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                                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
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                                  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
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                                    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

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                                      • 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
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                                        • 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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