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    Scanning Z probe support in RRF 3.5

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    • 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
        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 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
            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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            • 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
                      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

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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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                                          • 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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