Duet3D Logo Duet3D
    • Tags
    • Documentation
    • Order
    • Register
    • Login

    max number of step/ seconds in case of dual Y stepper config

    Scheduled Pinned Locked Moved
    General Discussion
    6
    20
    1.4k
    Loading More Posts
    • Oldest to Newest
    • Newest to Oldest
    • Most Votes
    Reply
    • Reply as topic
    Log in to reply
    This topic has been deleted. Only users with topic management privileges can see it.
    • psychotik2k3undefined
      psychotik2k3
      last edited by

      hi; i just saw another post indicating that the max frequency for steps is 360kHz and you have to divide it by the number of motors.
      does this applies to mirrored motors, like dual Y or dual Z ?or do you just send the same pulse to 2 pins ?

      thanks

      1 Reply Last reply Reply Quote 0
      • dc42undefined
        dc42 administrators
        last edited by

        The same pulse is sent to 2 pins, so using dual Y or dual Z does not reduce the maximum step rate.

        The 360kHz figure is probably over-optimistic now. When I measured that, RRF used double, quad or even octal stepping at high seeds. Since then we have users with step-servo drives, which need a steady pulse train. So now RRF always does single-stepping.

        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

        Catalin_ROundefined dragonnundefined 2 Replies Last reply Reply Quote 0
        • Catalin_ROundefined
          Catalin_RO @dc42
          last edited by

          @dc42 With single-stepping, what's a realistic maximum frequency for steps?

          1 Reply Last reply Reply Quote 0
          • psychotik2k3undefined
            psychotik2k3
            last edited by psychotik2k3

            yes i'm interested to know too as i have to check which ball scrtew lead i have to choose to have a correct speed .

            1 Reply Last reply Reply Quote 0
            • Phaedruxundefined
              Phaedrux Moderator
              last edited by

              Based on previous posts it would seem that 120khz is about right.

              https://forum.duet3d.com/topic/8660/high-number-of-hiccups-during-basic-moves/10

              Z-Bot CoreXY Build | Thingiverse Profile

              dc42undefined 1 Reply Last reply Reply Quote 0
              • dc42undefined
                dc42 administrators @Phaedrux
                last edited by

                @phaedrux said in max number of step/ seconds in case of dual Y stepper config:

                Based on previous posts it would seem that 120khz is about right.

                https://forum.duet3d.com/topic/8660/high-number-of-hiccups-during-basic-moves/10

                Yes, 120kHz to each of 3 motors on separate axes/towers. That's down from 180kHz when RRF used double/quad/octal stepping.

                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

                deckingmanundefined 1 Reply Last reply Reply Quote 0
                • deckingmanundefined
                  deckingman @dc42
                  last edited by

                  @dc42 May I ask what the limit might be in the situation of multiple extruder motors doing a firmware retraction? And also if that is likely to be different with Duet3?

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

                  dc42undefined 1 Reply Last reply Reply Quote 0
                  • dc42undefined
                    dc42 administrators @deckingman
                    last edited by

                    @deckingman said in max number of step/ seconds in case of dual Y stepper config:

                    @dc42 May I ask what the limit might be in the situation of multiple extruder motors doing a firmware retraction? And also if that is likely to be different with Duet3?

                    It's likely to be the same, i.e. 120kHz to 3 extruders simultaneously. Duet3 should be faster, my guess is by 50% to 80%.

                    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

                    1 Reply Last reply Reply Quote 0
                    • dragonnundefined
                      dragonn @dc42
                      last edited by

                      @dc42 said in max number of step/ seconds in case of dual Y stepper config:

                      The same pulse is sent to 2 pins, so using dual Y or dual Z does not reduce the maximum step rate.

                      The 360kHz figure is probably over-optimistic now. When I measured that, RRF used double, quad or even octal stepping at high seeds. Since then we have users with step-servo drives, which need a steady pulse train. So now RRF always does single-stepping.

                      Why not make double/quad/octal stepping an option? Or maybe automatic scale it when reaching certain frequency like 100kHz - goes into double stepping, 200kHz - quad and so on.

                      dc42undefined 1 Reply Last reply Reply Quote 0
                      • dc42undefined
                        dc42 administrators @dragonn
                        last edited by

                        @dragonn said in max number of step/ seconds in case of dual Y stepper config:

                        @dc42 said in max number of step/ seconds in case of dual Y stepper config:

                        The same pulse is sent to 2 pins, so using dual Y or dual Z does not reduce the maximum step rate.

                        The 360kHz figure is probably over-optimistic now. When I measured that, RRF used double, quad or even octal stepping at high seeds. Since then we have users with step-servo drives, which need a steady pulse train. So now RRF always does single-stepping.

                        Why not make double/quad/octal stepping an option? Or maybe automatic scale it when reaching certain frequency like 100kHz - goes into double stepping, 200kHz - quad and so on.

                        Because it would require additional code in multiple places to decide whether to do double etc. steppering or not, which would complicate the code and slow it down. I am not aware of any situations in which step rates or more than 100kHz are genuinely needed, so the ability to maintain more than 100kHz to three motors simultaneously is sufficient IMO. The maximum rate to a single motor should be around 200kHz.

                        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

                        deckingmanundefined 1 Reply Last reply Reply Quote 1
                        • deckingmanundefined
                          deckingman @dc42
                          last edited by

                          @dc42 said in max number of step/ seconds in case of dual Y stepper config:

                          I am not aware of any situations in which step rates or more than 100kHz are genuinely needed, so the ability to maintain more than 100kHz to three motors simultaneously is sufficient IMO. The maximum rate to a single motor should be around 200kHz.

                          Here is one situation. 3 (or 5) extruders feeding a mixing hot end and using firmware retraction. In an ideal world, I'd like to use 256X micro stepping to get the resolution required when the mixing ratio for a single filament is in the low single digit range. According to my calcs, using Bondtech BMGs with micro stepping at 16x the steps per mm are in the region of 415. So at 256x, the steps per mm would be 6640 and 100kHz would therefore limit retraction speed to 15mm/sec. Ideally, I'd like this to be 60mm/sec which means dropping the micro-stepping to 64x. TBH, I've been using 128X micro stepping because I thought the limit was 200kHz and I don't see an hiccups at this setting (but it'd been a while since I checked).

                          I doubt the following is possible but I'll ask the question anyway. I need fine extruder resolution for printing with low single digit mixing ratios, but at low speed. For retraction I don't care too much about resolution but do need speed. So would it be possible to do G10/G11 retraction moves at 16x microstepping but use 256x micro-stepping for "normal" printing?

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

                          dc42undefined 1 Reply Last reply Reply Quote 0
                          • dc42undefined
                            dc42 administrators @deckingman
                            last edited by

                            @deckingman said in max number of step/ seconds in case of dual Y stepper config:

                            Here is one situation. 3 (or 5) extruders feeding a mixing hot end and using firmware retraction. In an ideal world, I'd like to use 256X micro stepping to get the resolution required when the mixing ratio for a single filament is in the low single digit range.

                            IMO it's most unlikely that using x256 microstepping will give you any improvement over x16 or at most x32, because the incremental torque for a single x256 microstep is so small.

                            @deckingman said in max number of step/ seconds in case of dual Y stepper config:

                            I doubt the following is possible but I'll ask the question anyway. I need fine extruder resolution for printing with low single digit mixing ratios, but at low speed. For retraction I don't care too much about resolution but do need speed. So would it be possible to do G10/G11 retraction moves at 16x microstepping but use 256x micro-stepping for "normal" printing?

                            When we designed the Duet WiFi I originally planned to support dynamically-varying microstepping. But it's not easy, and interpolation proved to be effective at achieving the main benefit of higher microstepping, i.e. reducing stepper motor noise.

                            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

                            deckingmanundefined 1 Reply Last reply Reply Quote 0
                            • deckingmanundefined
                              deckingman @dc42
                              last edited by

                              @dc42 We discussed this some time back and I did a post about it on my blog https://somei3deas.wordpress.com/2018/06/08/why-16x-micro-stepping-is-a-bad-idea-with-mixing-hot-end/

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

                              dc42undefined 1 Reply Last reply Reply Quote 0
                              • dc42undefined
                                dc42 administrators @deckingman
                                last edited by

                                @deckingman said in max number of step/ seconds in case of dual Y stepper config:

                                @dc42 We discussed this some time back and I did a post about it on my blog https://somei3deas.wordpress.com/2018/06/08/why-16x-micro-stepping-is-a-bad-idea-with-mixing-hot-end/

                                Wasn't that before I fixed the bug whereby the residue after rounding the movement to a whole number of microsteps was thrown away instead of being added to the extrusion pending?

                                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

                                deckingmanundefined 1 Reply Last reply Reply Quote 0
                                • deckingmanundefined
                                  deckingman @dc42
                                  last edited by

                                  @dc42 said in max number of step/ seconds in case of dual Y stepper config:

                                  @deckingman said in max number of step/ seconds in case of dual Y stepper config:

                                  @dc42 We discussed this some time back and I did a post about it on my blog https://somei3deas.wordpress.com/2018/06/08/why-16x-micro-stepping-is-a-bad-idea-with-mixing-hot-end/

                                  Wasn't that before I fixed the bug whereby the residue after rounding the movement to a whole number of microsteps was thrown away instead of being added to the extrusion pending?

                                  I've no idea, but it wouldn't solve much in any case. The spread sheet linked in my post should still be active but to save you looking, I took an example segment size of 0.5mm as being not unreasonable. In that case, with a mixing ratio of 1% using 16x micro-stepping the extruder move would be 0.10375 of a micro-step. So there would effectively be no extruder movement. If you take the sum of the residues then you'd get one extruder micro-step every 10 segments but nothing for the other 9.

                                  The biggest error in percentage terms for 16x micro-stepping is actually with a mixing ratio of 5%, because the micro step is close to 0.5. So you either get no micro-step or whole one. If it's no micro-step, then you effectively under extrude by 5%. If it gets rounded up to a whole micro-step then you get 5% over extrusion. And if you happen to be using a 5 colour hot end with mixing ratio of 80:05:05:05:05 then you would get 20% under or over extrusion.

                                  In practice, it's not that bad because I don't believe that the filament coming out of the nozzle can follow what the extruder does with anything like that accuracy. So it will continue to "ooze" from one print segment to the next and get corrected during subsequent segments, but I hope you see what I'm getting at. To completely eliminate theoretical errors, I would need to use 256X micro-stepping.

                                  But that leads to a question that I've asked many times but never received a definitive answer which is, "would 1/256 micro step actually translate to any physical movement of the filament?" I suspect not, in which case one could say that no mixing hot end could ever achieve accurate colour mixing where the ratio of any one filament is a single digit percentage of the whole.

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

                                  1 Reply Last reply Reply Quote 0
                                  • Catalin_ROundefined
                                    Catalin_RO
                                    last edited by

                                    I think that the discussion is going into a direction that is not good at all!

                                    I have used both GRBL with its shield and 4 Pololu drivers before converting my CNC to Duet. These days I'm helping someone to upgrade a Chinese 6040 from this board to Duet - I will detail once we finish the conversion. In both cases the steppers run much smoother at 16x micro-stepping because of the interpolation implemented in the drivers.

                                    In the end we are discussing of mechanical systems with not insignificant moving/rotating weights and the associated inertia. Combining that with the very few studies on the Internet on the precision of the steppers steps and micro-steps, I wouldn't expect any significant difference between the interpolated 16x and an actual 256x micro-stepping! All that inertia smooths the movements anyway, and with the Trinamic drivers running at 16x micro-stepping things are even better.

                                    I still consider that the Duet board is a lot more than any other similar product in the same price range (if anyone can find such a product!). Also, it is a product that evolves. When trying to get as much functionality as possible in the firmware some things might get slower. From my experience that can happen also when trying to implement a certain functionality better or in a safer way. Long term I vote for reliability!

                                    deckingmanundefined 1 Reply Last reply Reply Quote 0
                                    • deckingmanundefined
                                      deckingman @Catalin_RO
                                      last edited by

                                      @catalin_ro said in max number of step/ seconds in case of dual Y stepper config:

                                      I think that the discussion is going into a direction that is not good at all!

                                      Hey, I'm not complaining. Mixing hot ends are rare, strange and fickle beasts at the best of times. David sad he "wasn't aware of any situations in which step rates of more than 100kHz are genuinely needed". I'm merely pointing out that such cases do indeed exist. But if i have to live with it, then so be it.

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

                                      1 Reply Last reply Reply Quote 0
                                      • deckingmanundefined
                                        deckingman
                                        last edited by

                                        @dc David. How about if I wrote a little post processing script that whenever there is a G10 command (retract), insert M350 E16:16:16:16:16 immediately before it, and whenever there is a G11 command (un-retract) enter M350 E256:256:256:256:256 immediately after it ? So effectively use 256x for "normal" printing but switch to 16X for the retract moves. Any reason why that wouldn't work?

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

                                        dc42undefined 1 Reply Last reply Reply Quote 0
                                        • dc42undefined
                                          dc42 administrators @deckingman
                                          last edited by

                                          That should work, although there may be more of a definite stop before and after retraction. But I will be surprised if you will see any difference between x16 interpolated and x256 microstepping.

                                          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

                                          deckingmanundefined 1 Reply Last reply Reply Quote 0
                                          • deckingmanundefined
                                            deckingman @dc42
                                            last edited by

                                            @dc42 In theory it should make a difference because as I keep saying, at 16x with single digit mixing ratios the extruder move could be in the region of 1/10th of a micro step or less. The only question remains is whether a single 1/256 micro step translates to any physical movement of the motor/filament. If not, what does. Is 128x, 64x or what? One of these days I'll run some more tests. I know exactly the colour combination to use. It's White and Red. The tiniest amount of red leads to pink. So a cylinder with 0.5mm segment sizes using single digit mixing of red with white would be the part to print. Five copies, at 16x, 32x, 64x, 128x and 256x. Maybe print them in vase mode. (Note to self, add this to the "todo" list).

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

                                            1 Reply Last reply Reply Quote 1
                                            • First post
                                              Last post
                                            Unless otherwise noted, all forum content is licensed under CC-BY-SA