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Leadscrew or ballscrew delta

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  • undefined
    DjDemonD
    last edited by 12 Jun 2017, 16:08 6 Dec 2017, 16:08

    Okay, so I'm musing on making a leadscrew or ballscrew based delta printer with a twist, as its going to use an acrylic cylinder for a frame.

    I am not doing this because I think it will be a better configuration than same an all-metal kossel XL, which I know works pretty damn well. It's more an exercise in building something unusual and interesting.

    My question is on leadscrews and ballscrews.

    1)Pitch, I understand that to get reasonable speed I am not going to be able to maximise resolution by having fine pitch screws, otherwise my motors just won't be able to turn them very fast. 8mm?
    2) How much motor torque is needed to drive them leadscrew vs ballscrew? The mass on each tower is not going to be large, (carriage, rods, share of the mass of the effector)

    Any thoughts? Anyone tried this already?

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

    undefined 1 Reply Last reply 13 Sept 2018, 03:52 Reply Quote 0
    • undefined
      deckingman
      last edited by 6 Dec 2017, 16:16

      I know nothing about Deltas but the ex engineer in me used to know a bit about lead screws and ball screws. In a nutshell, ball screws were invented as a low friction alternative to lead screws. That's all I'm prepared to say about your proposition - (other than best of luck Simon). 🙂

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

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      • undefined
        bot
        last edited by 6 Dec 2017, 16:49

        You could try acquiring some of these: http://www.linengineering.com/products/stepper-motor-linear-actuators/ln-stepper-motor-linear-actuators/

        I believe robotdigg sells something like that.

        It might allow you to move faster, with the right pitch, as you wouldn't be spinning the entire length of the screw – just the nut. With the drawback of moving the motor on each carriage.

        *not actually a robot

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        • undefined
          DjDemonD
          last edited by 6 Dec 2017, 16:49

          Thanks Ian (I think :)).

          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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          • undefined
            DjDemonD
            last edited by 12 Jun 2017, 19:48 6 Dec 2017, 16:57

            Interesting Bot, I think that might be a bit heavy duty, I'm looking at probably (as acrylic tubes are hard to get so I'm using a Biube fishtank) 30cm diameter and 45 cm height. So nema 17's and electronics top mounted with the intention that the base is open and can be placed onto whatever you want to print on, like David's scara using blue tape on the desk.

            I have in mind to use mgn9 rails, mount the bearing blocks for the screws to the lower end of the rails and design carriages with the nut in them.

            I also need to figure out how to precision drill the holes to mount the rails. I'm thinking either some sort of multi axis cnc or maybe just a paper template printed from cad drawings. I might be able to print a scaffold with holes marked on my large delta, assuming it is accurate enough and I'm not going to be introducing analogue copying error.

            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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            • undefined
              dc42 administrators
              last edited by 6 Dec 2017, 17:09

              If the screws are 8mm lead then the steps/mm using 1.8deg motors @ x16 microstepping would be 200 * 16/8 = 400. That's already 4x higher than a typical belt-drive delta. Another way of looking at it is that it's like using a 4-tooth GT2 pulley (same 8mm movement/rev). So you certainly don't want a smaller lead than 8mm, and you shouldn't use 0.9deg motors. You will probably need 24V power to get reasonable speeds.

              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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              • undefined
                deckingman
                last edited by 6 Dec 2017, 17:49

                Also consider that 400 micro steps per mm is 25 full steps, or 2.5 full steps per 0.1mm. So any odd value of layer height will rely on micro-stepping for positional accuracy which isn't generally best practice. Even numbers (0.2, 0.4 etc) would be fine though (well that is on a "normal" printer) 🙂

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

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                • undefined
                  timcurtis67
                  last edited by 6 Dec 2017, 18:10

                  You could also reduce the micro steps if you don't want 400 steps per mm. 1/4 step gets you back to matching what a delta belt moves.

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                  • undefined
                    DjDemonD
                    last edited by 6 Dec 2017, 18:36

                    David - thanks, yes 24v was certainly on the list.
                    Timcurtis67 - It'll make a lovely noise at 1/4 🙂

                    But that is interesting, whether microstepping might be useful is uncertain, with leadscrews I doubt it, but ballscrews should offer very low friction, like the rails themselves.

                    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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                    • undefined
                      toysrfun @DjDemonD
                      last edited by 13 Sept 2018, 03:52

                      @djdemond

                      For others reading this I’d run separate drivers through duex5 and 3000rpm servos and it will fly with fine pitch screws setup direct drive or 1:1. I have a CNC mill with 10mm pitch and very large servos that can run 1200ipm. Off top of head that is in 30,000mm/m and extremely fast I can’t imagine a 3D printer keeping up. At 10mm pitch I have 2.5 tpi and a 5mm pitch at approx 5tpi would potentially cut the speed in half. That’s still faster than you need so consider a 4mm or 2mm pitch. Ultimately you can go many of ways and use gear reduction if needed. The accuracy and positional feedback would be a huge improvement over belts if setup right. If using a course pitch to attempt industrial speeds you will have other challenges including z axis holding. I would in that case be sure the z axis servo had a built in off power brake. You can run steppers for extruders and servos for your axis. Presuming you want to spend $240 per axis. Personally I would do it and not waste my money again on steppers. Once you’ve changed you have a difficult time ever looking back. Everyone will say steppers are fine, blah, blah, and I’d be willing to bet it comes down to their own williness to spend the money on quality products. After all for most it’s a weekend hobby and nothing more. For others it’s the future and the sky is the limit. For myself I won’t even say what I’ve spent on this current project. Good thing I’m not married 😉

                      Obsessed with knowledge and growth. Learning never stops and everyday equates to another day learned. Being polite isn’t always easy. The fundamental essentials in learning require patience and kindness towards others. Knowitalls knowitless.

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                      • undefined
                        Danal
                        last edited by 13 Sept 2018, 04:04

                        I'd encourage you to use 9mm belts (instead of 6mm). They are quite close to half as stretchy as 6, and high quality 9mm work very well.

                        I do understand your desire for "something different", so if you must "Get Screwed"... Ballscrews all the way!!! Leadscrews are a "middle ground" or "compromise" and there is no reason to go away from belts and NOT go to the best of the best in your other option.

                        Delta / Kossel printer fanatic

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                        • undefined
                          Danal
                          last edited by 13 Sept 2018, 04:06

                          And... if you want to be REALLY different, have you considered this delta mechanical setup? Those are servos up top. Fast, beefy, servos.

                          https://youtu.be/Ec3Vf8Ip4Ic?t=17

                          Delta / Kossel printer fanatic

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