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    Laser filament monitor

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    Filament Monitor
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    • dc42undefined
      dc42 administrators
      last edited by

      If you want to calibrate volumetric extrusion, then I agree, in principle you need to measure filament diameter too. But standard practice is to calibrate linear extrusion. If the filament is of high quality, then the diameter will be tightly controlled so it will also give you sufficiently accurate volumetric extrusion too. Nevertheless, different filaments swell by different amounts after extrusion, so even accurate volumetric extrusion doesn't guarantee that you won't need to adjust the extrusion factor.

      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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      • DjDemonDundefined
        DjDemonD
        last edited by

        Sure measuring die-swell would be hard. The only idea that might be feasible for true auto calibration of the extruder would be to extrude onto a glass section at the side of the bed, from a precise z-height, and measure using a CCD scanner sensor, or something similar the width of filament extruded then change the steps/mm and extrude again. In theory it would account for all necessary factors.

        Simon. Precision Piezo Z-Probe Technology
        www.precisionpiezo.co.uk
        PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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        • deckingmanundefined
          deckingman
          last edited by

          IMO, even with a perfectly calibrated extruder there may still be a need to alter the extrusion multiplier to compensate for say models which have a lot of short slow moves vs models which have predominantly long fast moves. Another factor which is related to that is temperature and by that I mean the temperature throughout the filament from outside edge to the core. The filament itself is a very poor thermal conductor so when printing at high(ish) speed, there is less time in the melt chamber so the inner core may be significantly cooler than the outer surface. So even measuring die swell at one fixed speed/temperature combination might not be a practical solution.

          Ian
          https://somei3deas.wordpress.com/
          https://www.youtube.com/@deckingman

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          • veng1undefined
            veng1
            last edited by

            The schematic for Prusa's laser sensor has been published in his github. The part number on the print is PAT9125SEL

            https://github.com/prusa3d/PRUSA_Laser_filament_sensor/blob/master/rev.02/laser-sensor.pdf

            Slightly off topic but he has also published the power panic circuit. From the picture, I think it may need a slot routed in the pcb between L and N to meet UL creep distance.

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            • dc42undefined
              dc42 administrators
              last edited by

              Thanks, that confirms that the sensor we chose is the same one.

              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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              • elmoretundefined
                elmoret
                last edited by

                @veng1:

                The schematic for Prusa's laser sensor has been published in his github. The part number on the print is PAT9125SEL

                https://github.com/prusa3d/PRUSA_Laser_filament_sensor/blob/master/rev.02/laser-sensor.pdf

                Slightly off topic but he has also published the power panic circuit. From the picture, I think it may need a slot routed in the pcb between L and N to meet UL creep distance.

                Can confirm slot! Just received MK3.

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                • S1lencerundefined
                  S1lencer
                  last edited by

                  Happy to hear that the laser sensor is on the way ;).
                  Would be happy to test it.
                  Had problems lately with filamentgrinding.
                  That would be a thing of the past then.

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                  • McAdamundefined
                    McAdam
                    last edited by

                    For a while I've been toying with the idea of a filament thickness detector.
                    I often do 20 hour prints on 2.5kg spools, so the thickness of filament can vary a bit within a single print.
                    Supplier states 1.75mm +/- 0.05mm but I have found it to be closer to 0.08mm

                    The idea I've had so far is to use a digital tire gauge caliper, it's inexpensive, fairly accurate, and has a built-in serial output.

                    http://www.ebay.co.uk/itm/NEW-Digital-Tyre-Tire-Tread-Brakes-Shoe-Pad-Wear-Depth-Gauge-Caliper-0-25mm-/321762696307

                    Reading the output with a small microcontroller (ESP8266) I can then adjust the flowrate.

                    For actual filament movement; A 16 bit resolution rotary encoder with a extruder gear on it.

                    I know these solutions are more mechanical than the current suggestions, but maybe they can inspire some new thoughts.

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                    • fmaundefined
                      fma
                      last edited by

                      Does the section of your filament vary that much?

                      You need to measure the diameter in both directions, as the filament can be oval, and the section remaining the same…

                      Frédéric

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                      • McAdamundefined
                        McAdam
                        last edited by

                        @fma:

                        Does the section of your filament vary that much?

                        You need to measure the diameter in both directions, as the filament can be oval, and the section remaining the same…

                        Over a whole 2.5kg spool, it can vary quite a lot.

                        Yes, checking for OVALness will be very difficult, I have not thought of a solution to it yet 😞

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                        • DjDemonDundefined
                          DjDemonD
                          last edited by

                          There are some very expensive laser-based diameter and roundness testing devices but they're $1500… Its whether there is a way to do it for a lot less, rotating the laser filament monitor that Duet3D are playing with around the filament?

                          Simon. Precision Piezo Z-Probe Technology
                          www.precisionpiezo.co.uk
                          PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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                          • DeltaConundefined
                            DeltaCon
                            last edited by

                            @McAdam:

                            …The idea I've had so far is to use a digital tire gauge caliper, it's inexpensive, fairly accurate, and has a built-in serial output.
                            http://www.ebay.co.uk/itm/NEW-Digital-Tyre-Tire-Tread-Brakes-Shoe-Pad-Wear-Depth-Gauge-Caliper-0-25mm-/321762696307
                            Reading the output with a small microcontroller (ESP8266) I can then adjust the flowrate.

                            Nice idea, but would you press the gauge against the filament using a spring or something? I guess when a whole spool of filament passed this plastic toy, there would be a huge abraded hole in it. 😉

                            If you think trial and error is dangerous, try routine. That's even more so!

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                            • dc42undefined
                              dc42 administrators
                              last edited by

                              I've just had notification that the prototype PCBs for the laser filament sensor are on their way to me from HK! I only ordered them last Sunday.

                              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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                              • Dougal1957undefined
                                Dougal1957
                                last edited by

                                That's good news David

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                                • S1lencerundefined
                                  S1lencer
                                  last edited by

                                  Nice to hear.

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                                  • McAdamundefined
                                    McAdam
                                    last edited by

                                    @DeltaCon:

                                    @McAdam:

                                    …The idea I've had so far is to use a digital tire gauge caliper, it's inexpensive, fairly accurate, and has a built-in serial output.
                                    http://www.ebay.co.uk/itm/NEW-Digital-Tyre-Tire-Tread-Brakes-Shoe-Pad-Wear-Depth-Gauge-Caliper-0-25mm-/321762696307
                                    Reading the output with a small microcontroller (ESP8266) I can then adjust the flowrate.

                                    Nice idea, but would you press the gauge against the filament using a spring or something? I guess when a whole spool of filament passed this plastic toy, there would be a huge abraded hole in it. 😉

                                    Idea was to have a small pulley attached to the end of the guage, (similar to pulleys found in extruders) so there will be no friction.

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                                    • McAdamundefined
                                      McAdam
                                      last edited by

                                      @dc42:

                                      I've just had notification that the prototype PCBs for the laser filament sensor are on their way to me from HK! I only ordered them last Sunday.

                                      Great news!
                                      Is there still space on the Beta List?

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                                      • totalitarianundefined
                                        totalitarian
                                        last edited by

                                        Sorry to jump in but what is the advantage of this compared to a simple micro switch?

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                                        • adavidmundefined
                                          adavidm
                                          last edited by

                                          @totalitarian:

                                          Sorry to jump in but what is the advantage of this compared to a simple micro switch?

                                          These monitors track the amount of filament passing through the system. You can use that to tell if the extruder drive is slipping, not just if there is filament present.

                                          David has raised the possibility of auto-calibration of e-steps using the system, which would be very neat if it works.

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                                          • totalitarianundefined
                                            totalitarian
                                            last edited by

                                            Ah I see, very clever!

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