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    Microstepping and speed limits

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    • dc42undefined
      dc42 administrators
      last edited by

      You should preferably limit the step rate to about 100kHz per motor. For a Cartesian or CoreXY printer, the step rate is your steps/mm multiplied by the travel speed in mm/sec. So here is a table giving maximum recommended speeds when using 20 tooth pulleys, GT2 belts and 1.8deg motors:

      Microstepping, steps/mm. max speed
      16x, 80, 1250
      32x, 160, 625
      64x, 320, 312
      128x, 640, 156
      256x, 1280, 78

      For 0.9deg motors, divide max speed by 2. For other numbers of pulley teeth, multiply max speed by pulley_teeth/20.

      On the firmware work list is to implement variable microstepping, so that you can configure 256x but it will be reduced automatically at high 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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      • InSanityundefined
        InSanity
        last edited by

        @elmoret:

        I didn't come up with it, it is explained in the link I posted.

        My bad, didn't notice the link. Interesting..very interesting. Looks like 1.8 deg with 16 tooth and 256 stepping I'm looking at 150mm/s perhaps more as I think those charts are for a delta. I'm running 17t as well so yah maybe 150+ mm/s.

        Thanks,

        Jeff

        Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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        • deckingmanundefined
          deckingman
          last edited by

          @(In)Sanity:

          @elmoret:

          http://reprap.org/wiki/Step_rates

          Assuming a 20 tooth pulley, 1.8deg stepper, max speed is 187mm/sec at 256x. If you change to 0.9deg steppers, then about 93mm/sec.

          Thanks I'm actually running 1.8 deg motors with a weird 17t pulley setup. So I'm loosing a little speed with a little better resolution. Where did you come up with your value ?

          Jeff

          May I ask what are your steps/m for X and Y?

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

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          • InSanityundefined
            InSanity
            last edited by

            @dc42:

            You should limit the step rate to about 100kHz per motor. The step rate is your steps/mm multiplied by the travel speed in mm/sec. So here is a table giving maximum realistic speeds when using 20 tooth pulleys, GT2 belts and 1.8deg motors:

            Microstepping, steps/mm. max speed
            16x, 80, 1250
            32x, 160, 625
            64x, 320, 312
            128x, 640, 156
            256x, 1280, 78

            For 0.9deg motors, divide max speed by 2. For other numbers of pulley teeth, multiply max speed by pulley_teeth/20.

            On the firmware work list is to implement variable microstepping, so that you can configure 256x but it will be reduced automatically at high speeds.

            Thank you sir, looks like I should stick with 64x or 128x , perhaps 128x as I still can hear a little singing with 64x, not too much..but a little bit. 32x just drives me nuts. Hmm, I do once in a while print at 150mm/s when I need junk quickly.

            Jeff

            Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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            • InSanityundefined
              InSanity
              last edited by

              @deckingman:

              @(In)Sanity:

              @elmoret:

              http://reprap.org/wiki/Step_rates

              Assuming a 20 tooth pulley, 1.8deg stepper, max speed is 187mm/sec at 256x. If you change to 0.9deg steppers, then about 93mm/sec.

              Thanks I'm actually running 1.8 deg motors with a weird 17t pulley setup. So I'm loosing a little speed with a little better resolution. Where did you come up with your value ?

              Jeff

              May I ask what are your steps/m for X and Y?

              Sure, here is my current setup

              M92 X94.12 Y94.12 Z400 ; set axis steps/mm
              M92 E200.7238:200.7238 ; set extruder 0 and 1 steps/mm

              M350 I1 X64 Y64 Z64 E256:256 ; set microstepping

              Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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              • dc42undefined
                dc42 administrators
                last edited by

                Does the 64x sing less if you enable interpolation? The TMC2660 datasheet doesn't make it clear whether interpolation works at microstepping other than 16x.

                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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                • InSanityundefined
                  InSanity
                  last edited by

                  @dc42:

                  Does the 64x sing less if you enable interpolation? The TMC2660 datasheet doesn't make it clear whether interpolation works at microstepping other than 16x.

                  You know, my mind wants to think so…so I leave it on. I've not done any real serious testing. I'll have to do so.

                  Jeff

                  Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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                  • deckingmanundefined
                    deckingman
                    last edited by

                    At 94.12 steps/mm 1 step = 0.01062734mm so at 16 micro steps 1 micro step = 0.000664046mm , at 32, one micro step = 0.000332023mm, at 64 it becomes 0.000166011mm and we need to use scientific notation for the higher micro steps.
                    Just thought I'd point that out.

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

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                    • InSanityundefined
                      InSanity
                      last edited by

                      @deckingman:

                      At 94.12 steps/mm 1 step = 0.01062734mm so at 16 micro steps 1 micro step = 0.000664046mm , at 32, one micro step = 0.000332023mm, at 64 it becomes 0.000166011mm and we need to use scientific notation for the higher micro steps.
                      Just thought I'd point that out.

                      The uneven ratio I know is a bit odd and could produce some possible artifacts, it's what the printer came with and is a bit of work to change out to 16t pulleys. 20t might actually be easier to switch to if they fit. I assume you were talking about the odd ratio, or perhaps just the resolution which of course can't be achieved? I can however notice stuff like the letters on the back of a 3dbenchy looking better at > 16 microstepping. It's subtle, but it exists. Mostly the higher microstepping is about noise level for me. I just can't live with 16x when I have that 1% chance of better results above 16x.

                      Jeff

                      Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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                      • InSanityundefined
                        InSanity
                        last edited by

                        @dc42:

                        Does the 64x sing less if you enable interpolation? The TMC2660 datasheet doesn't make it clear whether interpolation works at microstepping other than 16x.

                        It does seam to make a little bit more singing noise with interpolation off. I would say for those who are worried about such a thing to just leave it on, even if it does nothing more than make the end user think it does.

                        Jeff

                        Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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                        • 3dprinting meatheadundefined
                          3dprinting meathead
                          last edited by

                          @(In)Sanity:

                          @dc42:

                          Does the 64x sing less if you enable interpolation? The TMC2660 datasheet doesn't make it clear whether interpolation works at microstepping other than 16x.

                          It does seam to make a little bit more singing noise with interpolation off. I would say for those who are worried about such a thing to just leave it on, even if it does nothing more than make the end user think it does.

                          Jeff

                          Are you running 12v or 24v?
                          I heard that the tmc2100s were quieter with 24v, but not sure if it's true, and I'm not sure if it holds true with the tmc2660, which from th little information I could find, is a 2100 with higher amperage(?)

                          If I can learn it, than anyone can learn it.

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                          • dc42undefined
                            dc42 administrators
                            last edited by

                            I've had confirmation from Trinamic that interpolation only works when microstepping is set to 16x.

                            The 256x interpolation modes in the TMC2100 and TMC2660 are similar, but as well as supporting higher currents the TMC2660 provides an SPI interface to control and monitor the chip, while the TMC2100 just provides some configuration pins instead.

                            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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                            • InSanityundefined
                              InSanity
                              last edited by

                              I'm running 24 volts. So the finding on the interpolation match up with what I've seen, 32x for example is significantly louder then 64x with interpolation on.

                              So at the moment I'm running in 256x mode and can do travel moves at 200 mm/s and normally print at 80-90 mm/s. I've timed prints with 16x up to 256x and not seen any differences in completion time at all, so how does one know if you are being slowed down by using too high of microstepping values ?

                              Jeff

                              Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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                              • dc42undefined
                                dc42 administrators
                                last edited by

                                To check whether you have the combination of speed * microstepping too high, do some long, high-speed moves. Then run M122 and look at "MaxReps" in the Move section. Try to keep that value below 50, or 100 at most. The value is cleared out after it is displayed.

                                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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                                • InSanityundefined
                                  InSanity
                                  last edited by

                                  @dc42:

                                  To check whether you have the combination of speed * microstepping too high, do some long, high-speed moves. Then run M122 and look at "MaxReps" in the Move section. Try to keep that value below 50, or 100 at most. The value is cleared out after it is displayed.

                                  Ok, in geek speak what does this translate into ?

                                  Thanks,

                                  Jeff

                                  Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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                                  • dc42undefined
                                    dc42 administrators
                                    last edited by

                                    MaxReps is the number of times that the ISR loops while generating step pulses, before there are no further steps due yet.

                                    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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                                    • InSanityundefined
                                      InSanity
                                      last edited by

                                      @dc42:

                                      MaxReps is the number of times that the ISR loops while generating step pulses, before there are no further steps due yet.

                                      Ahh, so kind of like the max length of the FIFO that was hit? I notice I hit 364 on my last print. I've stepped down to 128x and trying the print again.

                                      Edit: Same print I got 17 now with 128x vs 364 @ 256x. Guess I'll stick with 128x.

                                      Thanks,

                                      Jeff

                                      Duet WiFi Powered FFCP with E3D legends hotend system. BLTouch grid leveling.

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