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    Hollow shaft extruder

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    • o_lampeundefined
      o_lampe
      last edited by

      I was able to squeeze a bigger BLDC motor in the 44mm space of the sherpa mini.

      3506VS2804.jpg

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      • o_lampeundefined
        o_lampe @tombrazier
        last edited by o_lampe

        @tombrazier said in Hollow shaft extruder:

        At 700mA I can drive the filament at 50mm/s and accelerate at 1500mm/s^2 without a motor stall

        Is that the retraction speed or can you actually extrude at 50mm/s? What are actual PLA print speeds with 0.4mm nozzle and say 0.3mm layer?
        It's always hard to compare apples with oranges, but in the end I'd like to know if it's worth going the extra mile with the dual motor setup I'm working on.

        rqthreeundefined tombrazierundefined 2 Replies Last reply Reply Quote 0
        • rqthreeundefined
          rqthree @o_lampe
          last edited by rqthree

          @o_lampe said in Hollow shaft extruder:

          @tombrazier said in Hollow shaft extruder:

          At 700mA I can drive the filament at 50mm/s and accelerate at 1500mm/s^2 without a motor stall

          Is that the retraction speed or can you actually extrude at 50mm/s? What are actual PLA print speeds with 0.4mm nozzle and say 0.3mm layer?
          It's always hard to compare apples with oranges, but in the end I'd like to know if it's worth going the extra mile with the dual motor setup I'm working on.

          Tom, although I've been using my "original" NEMA 14 VDE for well over two years, I still tinker with ideas. I never could get a NEMA 11 pancake to drive reliably, but TWO of them, rotating in the same direction but mounted back-to-back, seems like the cat's meow. Because they are back-to-back, they eliminate torque on the filament. Of course, you need two motors, and two bearing carriers. But one carrier is "right hand thread", and the other is, of necessity, "left hand thread", so the grooves scored in the filament only cross each other once per revolution. There is no issue with getting the two grooves to track each other, because they can't, and don't need to. They are independent of each other. There is still only one knife edge per carrier, per my reasoning above.

          Of course this bumps the complexity and cost by 2x, and the weight up to 65 whole grams! Prototype with 30 degree cant angles.
          IMG_1940.jpg

          EDIT Nov.1, 2023: A very brief video of the Push-Me_Pull_You VDE running (change the .doc extension to .mov).
          Cons: as noted, twice as heavy and twice as complicated, needs left AND right hand drive carriers.
          Pros: handles extremely flexible TPU with no hot end anchoring at all, 5 times the filament force (5 kilos vs 1 kilo) at 0.2 amps (paralleled NEMA 11 motors, no heat issues at all), motors can attain 4500 RPM, and 3000 RPM while actually driving filament (150 mm/sec at 30 degree cant angle). Feed and retraction very repeatable, as the two drivers don't interact.
          The Take Away: Not worth the size, weight (80 grams), and expense, unless you are after extreme extrusion speeds. I'll stick to my tried-and-true single knife NEMA 14.

          IMG_1951.DOC

          o_lampeundefined fmaundefined 2 Replies Last reply Reply Quote 3
          • o_lampeundefined
            o_lampe @rqthree
            last edited by

            @rqthree The left/right rotation is a good idea.
            Otherwise It is a bit similar to my dual motor approach, but I'll put a Bowden tube between the two. No weight panelty and free choice for the remote motor.

            I'm also a bit worried about temperatures and sketched up a thin watercooling plate to fit between your motors. A bit more weight doesn't make much of a difference, you already fouled there anyway 🙂

            watercooler.jpg

            rqthreeundefined 1 Reply Last reply Reply Quote 0
            • fmaundefined
              fma @rqthree
              last edited by

              @rqthree very cute extruder!

              Do you have some more informations about the motors and all vitamins used? Would you share your 3D models?

              Thanks,

              Frédéric

              rqthreeundefined 1 Reply Last reply Reply Quote 0
              • tombrazierundefined
                tombrazier @o_lampe
                last edited by

                @o_lampe said in Hollow shaft extruder:

                Is that the retraction speed or can you actually extrude at 50mm/s? What are actual PLA print speeds with 0.4mm nozzle and say 0.3mm layer?

                That's retraction speed. I think the motor can move at that speed while printing without stalling (but will have to confirm for sure). However with compression of the helical thread actual extrusion speed will be a whole lot lower. I specced the motor for extruding about 16mm/s which would give about 320mm/s linear printing speed with 0.4mm x 0.3mm lines. However with nozzle back-pressure I don't expect to get 16mm/s.

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                • o_lampeundefined
                  o_lampe
                  last edited by

                  I've verified my NEMA08 motor temp-curve and the rated current of 0.6A is quite reasonable. For PLA printing the motor-surface temp at 0.5A is a bit too high.
                  The filament got soft when I extruded very slow (0.5mm/s). At normal print speeds I don't expect problems, but the first layer speed is usually slower and might fail.
                  Will try with 0.45A for longer periods and add some airflow over the stepper by designing an intake fan shroud for the hotend fan.

                  I also noticed that 20° cant angle doesn't self-lock the filament motion completely, but that is part of my pacemaker strategy. Luckily I've written the code for the remote torque_push motor in such way, that it goes idle without incomming steps. 🤞

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                  • rqthreeundefined
                    rqthree @fma
                    last edited by

                    @fma said in Hollow shaft extruder:

                    @rqthree very cute extruder!

                    Do you have some more informations about the motors and all vitamins used? Would you share your 3D models?

                    Thanks,

                    Frederic, here you go. Change the file extension to .zip from .doc. This forum does not accept zip files.

                    VDE_NEMA11.doc

                    fmaundefined 2 Replies Last reply Reply Quote 0
                    • fmaundefined
                      fma @rqthree
                      last edited by

                      @rqthree Thank you very much!

                      Frédéric

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                      • breedundefined
                        breed
                        last edited by

                        Those rollers that were on funssor store on AliExpress a month or so ago finally showed up. They don't look anywhere near as bad as far as machining quality goes compared to the pictures. Id be hard to pressed to make better ones on the lathe. I'll send some pictures later today, gotta get to bed so I can watch some college football today.

                        o_lampeundefined 1 Reply Last reply Reply Quote 3
                        • o_lampeundefined
                          o_lampe @breed
                          last edited by

                          @breed I have them on my watchlist, but wait until the price drops.
                          If it's good enough with one flanged bearing (according to @rqthree ) it doesn't make sense to use three long threaded rods.
                          I was thinking if making them conical in both directions would be better? But the contact area is so small, it doesn't matter...

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                          • fmaundefined
                            fma @rqthree
                            last edited by

                            @rqthree There is a problem with these files: Carrier_Assy.FCStd and Knife_Bearing.FCStd ; I'm unable to open them, neither other people at my hackerspace (they freeze or crash FreeCAD).
                            Could you save them as STEP files?
                            Thanks,

                            Frédéric

                            rqthreeundefined 1 Reply Last reply Reply Quote 0
                            • rqthreeundefined
                              rqthree @fma
                              last edited by

                              @fma said in Hollow shaft extruder:

                              @rqthree There is a problem with these files: Carrier_Assy.FCStd and Knife_Bearing.FCStd ; I'm unable to open them, neither other people at my hackerspace (they freeze or crash FreeCAD).
                              Could you save them as STEP files?
                              Thanks,

                              The files are fine, but were generated with a very high definition version of FreeCad. They will eventually open, but may take many minutes on a pretty high power workstation. In any case, the two files you reference are not at all important, and just show the over-all arrangement of parts.They don't contain any critical dimensions or data not seen in the other files.

                              fmaundefined 1 Reply Last reply Reply Quote 0
                              • fmaundefined
                                fma @rqthree
                                last edited by

                                @rqthree Ok, I see!

                                Frédéric

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                                • fmaundefined
                                  fma
                                  last edited by

                                  @rqthree BTW, how do you get the sharp edge on the flanged bearing? With a lathe?

                                  Frédéric

                                  rqthreeundefined 1 Reply Last reply Reply Quote 0
                                  • rqthreeundefined
                                    rqthree @fma
                                    last edited by rqthree

                                    @fma , yes, I use a collet chuck in a jewelers lathe, with an abrasive disc on a rotary tool. Others, like Tom Brazier, have come up with clever methods that don't require a lathe.

                                    IMG_1952.jpg

                                    fmaundefined 1 Reply Last reply Reply Quote 0
                                    • fmaundefined
                                      fma @rqthree
                                      last edited by

                                      @rqthree Thanks, I'll read the entire thread again to see how other guys do...

                                      Frédéric

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                                      • rqthreeundefined
                                        rqthree @o_lampe
                                        last edited by

                                        @o_lampe said in Hollow shaft extruder:

                                        @rqthree The left/right rotation is a good idea.
                                        Otherwise It is a bit similar to my dual motor approach, but I'll put a Bowden tube between the two. No weight panelty and free choice for the remote motor.

                                        I'm also a bit worried about temperatures and sketched up a thin watercooling plate to fit between your motors. A bit more weight doesn't make much of a difference, you already fouled there anyway 🙂

                                        watercooler.jpg

                                        The dual motor Push-Me-Pull-You VDE works fine at 0.2 amps driving two paralleled NEMA 11 motors. The motors get slightly warm after several hours of continuous operation, but nothing that affects even PLA.

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                                        • tombrazierundefined
                                          tombrazier
                                          last edited by

                                          @rqthree I vote we call this push pull version VDE337.

                                          rqthreeundefined 1 Reply Last reply Reply Quote 0
                                          • rqthreeundefined
                                            rqthree @tombrazier
                                            last edited by rqthree

                                            @tombrazier said in Hollow shaft extruder:

                                            @rqthree I vote we call this push pull version VDE337.

                                            Tom, I have to ask...??? I know there is always a method to your madness, but I have wracked my brains on this one.

                                            EDIT: Never mind, you Cessna driver. VDE337 it is!

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